[Federal Register Volume 82, Number 121 (Monday, June 26, 2017)]
[Proposed Rules]
[Pages 28946-28977]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2017-13275]



[[Page 28945]]

Vol. 82

Monday,

No. 121

June 26, 2017

Part II





Department of Commerce





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National Oceanic and Atmospheric Administration





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50 CFR Parts 223 and 224





Endangered and Threatened Wildlife; 90-Day Finding on a Petition To 
List 10 Species of Giant Clams as Threatened or Endangered Under the 
Endangered Species Act; Proposed Rule

  Federal Register / Vol. 82 , No. 121 / Monday, June 26, 2017 / 
Proposed Rules  

[[Page 28946]]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

50 CFR Parts 223 and 224

[Docket No. 170117082-7082-01]
RIN 0648-XF174


Endangered and Threatened Wildlife; 90-Day Finding on a Petition 
To List 10 Species of Giant Clams as Threatened or Endangered Under the 
Endangered Species Act

AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and 
Atmospheric Administration (NOAA), Commerce.

ACTION: 90-day petition findings, request for information, and 
initiation of status review.

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SUMMARY: We, NMFS, announce our 90-day findings on a petition to list 
ten species of giant clam as endangered or threatened under the U.S. 
Endangered Species Act (ESA). We find that the petition presents 
substantial scientific or commercial information indicating that the 
petitioned action may be warranted for seven species (Hippopus 
hippopus, H. porcellanus, Tridacna costata, T. derasa, T. gigas, T. 
squamosa, and T. tevoroa). Accordingly, we will initiate status reviews 
of these seven giant clam species. To ensure that the status reviews 
are comprehensive, we are soliciting scientific and commercial 
information regarding these species. We find that the petition did not 
present substantial scientific or commercial information indicating 
that the petitioned action may be warranted for the other three 
petitioned giant clam species (T. crocea, T. maxima, or T. noae).

DATES: Information and comments on the subject action must be received 
by August 25, 2017.

ADDRESSES: You may submit comments, information, or data, by including 
``NOAA-NMFS-2017-0029'' by either of the following methods:
     Federal eRulemaking Portal: Go to www.regulations.gov/#!docketDetail;D=NOAA-NMFS-2017-0029, click the ``Comment Now'' icon, 
complete the required fields, and enter or attach your comments.
     Mail or hand-delivery: Office of Protected Resources, 
NMFS, 1315 East-West Highway, Silver Spring, MD 20910. Attn: Lisa 
Manning.
    Instructions: NMFS may not consider comments if they are sent by 
any other method, to any other address or individual, or received after 
the comment period ends. All comments received are a part of the public 
record and NMFS will post for public viewing on http://www.regulations.gov without change. All personal identifying 
information (e.g., name, address, etc.), confidential business 
information, or otherwise sensitive information submitted voluntarily 
by the sender will be publicly accessible. NMFS will accept anonymous 
comments (enter ``N/A'' in the required fields if you wish to remain 
anonymous).

FOR FURTHER INFORMATION CONTACT: Lisa Manning, NMFS, Office of 
Protected Resources (301) 427-8403.

SUPPLEMENTARY INFORMATION:

Background

    On August 7, 2016, we received a petition from a private citizen, 
Dr. Dwayne W. Meadows, Ph.D., requesting that we list the Tridacninae 
giant clams (excluding Tridacna rosewateri) as endangered or threatened 
under the ESA. The ten species of giant clams considered in this 
finding are the eight Tridacna species, including: T. costata, T. 
crocea, T. derasa, T. gigas, T. maxima, T. noae, T. squamosa, and T. 
tevoroa (also known as T. mbalavauna); and the two Hippopus species: H. 
hippopus and H. porcellanus. The petitioner also requested that 
critical habitat be designated for Tridacninae species that occur in 
U.S. waters concurrent with final ESA listing. The petition states that 
Tridacninae giant clams merit listing as endangered or threatened 
species under the ESA because of the following: (1) Loss or curtailment 
of habitat or range; (2) historical and continued overutilization of 
the species for commercial purposes; (3) inadequacy of existing 
regulatory mechanisms to safeguard the species; (4) other factors such 
as global climate change; and (5) the species' inherent vulnerability 
to population decline due to their slow recovery and low resilience to 
threats.

ESA Statutory Provisions and Policy Considerations

    Section 4(b)(3)(A) of the ESA of 1973, as amended (16 U.S.C. 1531 
et seq.), requires, to the maximum extent practicable, that within 90 
days of receipt of a petition to list a species as threatened or 
endangered, the Secretary of Commerce make a finding on whether that 
petition presents substantial scientific or commercial information 
indicating that the petitioned action may be warranted, and promptly 
publish the finding in the Federal Register (16 U.S.C. 1533(b)(3)(A)). 
When we find that substantial scientific or commercial information in a 
petition and in our files indicates the petitioned action may be 
warranted (a ``positive 90-day finding''), we are required to promptly 
commence a review of the status of the species concerned, which 
includes conducting a comprehensive review of the best available 
scientific and commercial information. Within 12 months of receiving 
the petition, we must conclude the review with a finding as to whether, 
in fact, the petitioned action is warranted. Because the finding at the 
12-month stage is based on a significantly more thorough review of the 
available information, a ``may be warranted'' finding at the 90-day 
stage does not prejudge the outcome of the status review and 12-month 
finding.
    Under the ESA, a listing determination may address a ``species,'' 
which is defined to also include subspecies and, for any vertebrate 
species, any distinct population segment (DPS) that interbreeds when 
mature (16 U.S.C. 1532(16)). A joint NMFS-U.S. Fish and Wildlife 
Service (USFWS) policy clarifies the agencies' interpretation of the 
phrase ``distinct population segment'' for the purposes of listing, 
delisting, and reclassifying a species under the ESA (``DPS Policy''; 
61 FR 4722; February 7, 1996). A species, subspecies, or DPS is 
``endangered'' if it is in danger of extinction throughout all or a 
significant portion of its range, and ``threatened'' if it is likely to 
become endangered within the foreseeable future throughout all or a 
significant portion of its range (ESA sections 3(6) and 3(20), 
respectively; 16 U.S.C. 1532(6) and (20)). Pursuant to the ESA and our 
implementing regulations, the determination of whether a species is 
threatened or endangered shall be based on any one or a combination of 
the following five section 4(a)(1) factors: The present or threatened 
destruction, modification, or curtailment of habitat or range; 
overutilization for commercial, recreational, scientific, or 
educational purposes; disease or predation; inadequacy of existing 
regulatory mechanisms; and any other natural or manmade factors 
affecting the species' existence (16 U.S.C. 1533(a)(1), 50 CFR 
424.11(c)).
    ESA-implementing regulations issued jointly by NMFS and USFWS (50 
CFR 424.14(b)) define ``substantial information'' in the context of 
reviewing a petition to list, delist, or reclassify a species as the 
amount of information that would lead a reasonable person to believe 
that the measure proposed in the petition may be warranted. When 
evaluating whether substantial information is contained in a petition,

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we must consider whether the petition: (1) Clearly indicates the 
administrative measure recommended and gives the scientific and any 
common name of the species involved; (2) contains detailed narrative 
justification for the recommended measure, describing, based on 
available information, past and present numbers and distribution of the 
species involved and any threats faced by the species; (3) provides 
information regarding the status of the species over all or a 
significant portion of its range; and (4) is accompanied by the 
appropriate supporting documentation in the form of bibliographic 
references, reprints of pertinent publications, copies of reports or 
letters from authorities, and maps (50 CFR 424.14(b)(2)).
    At the 90-day stage, we evaluate the petitioner's request based 
upon the information in the petition including its references, and the 
information readily available in our files. We do not conduct 
additional research, and we do not solicit information from parties 
outside the agency to help us in evaluating the petition. We will 
accept the petitioner's sources and characterizations of the 
information presented, if they appear to be based on accepted 
scientific principles, unless we have specific information in our files 
that indicates the petition's information is incorrect, unreliable, 
obsolete, or otherwise irrelevant to the requested action. Information 
that is susceptible to more than one interpretation or that is 
contradicted by other available information will not be dismissed at 
the 90-day finding stage, so long as it is reliable and a reasonable 
person would conclude that it supports the petitioner's assertions. 
Conclusive information indicating the species may meet the ESA's 
requirements for listing is not required to make a positive 90-day 
finding. We will not conclude that a lack of specific information alone 
negates a positive 90-day finding, if a reasonable person would 
conclude that the unknown information itself suggests an extinction 
risk of concern for the species at issue.
    To make a 90-day finding on a petition to list a species, we 
evaluate whether the petition presents substantial scientific or 
commercial information indicating the subject species may be either 
threatened or endangered, as defined by the ESA. First, we evaluate 
whether the information presented in the petition, along with the 
information readily available in our files, indicates that the 
petitioned entity constitutes a ``species'' eligible for listing under 
the ESA. Next, we evaluate whether the information indicates that the 
species at issue faces extinction risk that is cause for concern; this 
may be indicated in information expressly discussing the species' 
status and trends, or in information describing impacts and threats to 
the species. We evaluate any information on specific demographic 
factors pertinent to evaluating extinction risk for the species at 
issue (e.g., population abundance and trends, productivity, spatial 
structure, age structure, sex ratio, diversity, current and historical 
range, habitat integrity or fragmentation), and the potential 
contribution of identified demographic risks to extinction risk for the 
species. We then evaluate the potential links between these demographic 
risks and the causative impacts and threats identified in ESA section 
4(a)(1).
    Information presented on impacts or threats should be specific to 
the species and should reasonably suggest that one or more of these 
factors may be operative threats that act or have acted on the species 
to the point that it may warrant protection under the ESA. Broad 
statements about generalized threats to the species, or identification 
of factors that could negatively impact a species, do not constitute 
substantial information that listing may be warranted. We look for 
information indicating that not only is the particular species exposed 
to a factor, but that the species may be responding in a negative 
fashion; then we assess the potential significance of that negative 
response.
    Many petitions identify risk classifications made by non-
governmental organizations, such as the International Union for the 
Conservation of Nature (IUCN), the American Fisheries Society, or 
NatureServe, as evidence of extinction risk for a species. Risk 
classifications by other organizations or made under other Federal or 
state statutes may be informative, but such classification alone may 
not provide the rationale for a positive 90-day finding under the ESA. 
For example, as explained by NatureServe, their assessments of a 
species' conservation status do ``not constitute a recommendation by 
NatureServe for listing under the U.S. Endangered Species Act'' because 
NatureServe assessments ``have different criteria, evidence 
requirements, purposes and taxonomic coverage than government lists of 
endangered and threatened species, and therefore these two types of 
lists should not be expected to coincide'' (http://www.natureserve.org/prodServices/statusAssessment.jsp). Thus, when a petition cites such 
classifications, we will evaluate the source of information that the 
classification is based upon in light of the standards on extinction 
risk and impacts or threats discussed above.

Analysis of the Petition

General Information

    The petition clearly indicates the administrative measure 
recommended and gives the scientific and, in some cases, the common 
names of the species involved. The petition also contains a narrative 
justification for the recommended measures and provides limited 
information on the species' geographic distribution, habitat use, and 
threats. Limited information is also provided on population status and 
trends for all but a couple of species. The introduction of the 
petition emphasizes that giant clam species have not been evaluated by 
the IUCN since 1996, and more recent information provides evidence of 
significant population declines of all giant clam species range-wide, 
with increasing threats. The petition then provides general background 
information on giant clams as well as some limited species-specific 
information where available. Topics covered by the petition include 
giant clam taxonomy, natural history, descriptions of Tridacna species 
(descriptions of Hippopus species are absent), geographic range, 
habitat descriptions, life history (including growth and reproduction), 
ecology (including their symbiotic relationship with zooxanthellae and 
their ecological role on coral reefs), population structure and 
genetics, and abundance and trends. A general description of threats 
categorized under the five ESA Section 4(a)(1) factors is provided and 
is meant to apply to all of the petitioned clam species. This section 
discusses the following threats: Coral reef habitat degradation 
(including sedimentation, pollution, and reclamation), subsistence and 
commercial harvest by coastal and island communities for local 
consumption as well as sale and export for the meat, aquarium and curio 
trades, inadequacy of existing regulatory mechanisms to safeguard the 
species, and impacts of climate change (including bleaching and ocean 
acidification). A synopsis of and our analysis of the information 
provided in the petition and readily available in our files is provided 
below.

Species Description

    Giant clams are a small but conspicuous group of large bivalves 
that are members of the cardiid bivalve subfamily Tridacninae (Su et 
al., 2014). They are the largest living marine

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bivalves found in coastal areas of the Indo-Pacific region, and are 
frequently regarded as important ecological components of coral reefs, 
especially as providers of substrate and contributors to overall 
productivity (Neo and Todd 2013). The most recent information suggests 
there are 13 extant species of giant clams, 10 of which are considered 
in this 90-day finding, including 8 species in the genus Tridacna--T. 
crocea, T. derasa, T. gigas, T. maxima, T. noae, T. squamosa, T. 
costata (formerly T. squamosina) and T. tevoroa (formerly T. 
mbalavauna), and 2 species in the genus Hippopus--H. hippopus and H. 
porcellanus.

Taxonomy

    Giant clam taxonomy (family Cardiidae, subfamily Tridacninae) has 
seen a surge in new species descriptions in recent decades (Borsa et 
al., 2015a), and there is some disagreement in the literature regarding 
the validity of some species. Two giant clam species considered in this 
90-day finding have been only recently described (T. tevoroa and T. 
costata), but have been shown to be junior synonyms of species 
described decades before (i.e., T. mbalavuana and T. squamosina, 
respectively; Borsa et al., 2015a). Another species, T. noae, has been 
the subject of debate in terms of its validity as a species. However, 
T. noae has been recently resurrected from synonymy with the small 
giant clam, T. maxima, after additional molecular and morphological 
evidence supported the taxonomic separation of the two species (Su et 
al., 2014).

Range and Distribution

    Modern giant clams are distributed along shallow shorelines and on 
reefs in the Indo-West Pacific in the area confined by 30[deg] E and 
120[deg] W (i.e., from South Africa to beyond French Polynesia) and 
between 36[deg] N and 30[deg] S (i.e., from Japan in the North to 
Australia in the South; Neo et al., 2015) and excluding New Zealand and 
Hawaii, although there are reports that at least two species have been 
introduced in Hawaii (T. derasa and T. squamosa; bin Othman et al., 
2010). Although most extant giant clams mainly occur within the 
tropical Indo-Pacific region, three species (T. maxima, T. squamosa and 
T. costata) are found as far west as East Africa or the Red Sea (Soo 
and Todd 2014). Of all the giant clam species, T. maxima has the most 
cosmopolitan distribution, which encompasses nearly the entire 
geographical range of all the other giant clam species. On the other 
side of the spectrum, the more recently described T. costata, T. 
tevoroa, and H. porcellanus have the most restricted geographical 
ranges (bin Othman et al., 2010).
    Anecdotal reports by SCUBA divers and data from Reef Check (an 
international non-governmental organization that trains volunteers to 
carry out coral reef surveys) include records of giant clams beyond 
previously defined geographical boundaries, extending their known 
occurrence to near Cape Agulhas, South Africa. Giant clam distribution 
is not uniform, with greater diversity found in the central Indo-
Pacific (Spalding et al., 2007). A couple of recent sources have 
extended the known ranges of a couple of species. For example, Gilbert 
et al. (2007) documented the first observation of T. squamosa in French 
Polynesia, extending the species' range farther east than previously 
reported. Likewise, in our files, we found evidence that T. tevoroa has 
recently been observed in the Loyalty Islands of New Caledonia, whereas 
it was previously thought to be restricted to Tonga and Fiji (Kinch and 
Teitelbaum 2009). The petition claims that several of the species occur 
(or historically occurred) in the United States and its territories or 
possessions, including: T. derasa, T. gigas, T. maxima, T. squamosa, 
and H. hippopus. The rest of the petitioned clam species have strictly 
foreign distributions. The NMFS Coral Reef Ecosystem Program (CREP) 
conducts routine Reef Assessment and Monitoring Program surveys in U.S. 
territories, but their comprehensive monitoring reports only include 
general information on Tridacna clams, not at the species level.

Habitat

    The petition cites Soo and Todd (2014), stating that giant clams 
are markedly stenothermal (i.e., they are able to tolerate only a small 
range of temperature) and thus restricted to warm waters. Based on the 
broad latitudinal and depth ranges of some giant clam species, they 
each likely have varying ranges of temperature tolerance, possibly 
similar to that of other coral reef associated species. Although giant 
clams are typically associated with and are prominent inhabitants of 
coral reefs, this is not an obligate relationship (Munro 1992). Giant 
clams are typically found living on sand or attached to coral rock and 
rubble by byssal threads (Soo and Todd 2014), but they can be found in 
a wide variety of habitats, including live coral, dead coral rubble, 
boulders, sandy substrates, seagrass beds, macroalgae zones, etc. 
(Gilbert et al., 2006; Hernawan 2010).

Life History

    The exact lifespan of tridacnines has not been determined; although 
it is estimated to vary widely between eight to several hundred years 
(see original citations in Soo and Todd 2014). Little information 
exists on the size at maturity for giant clams, but size and age at 
maturity vary by species and geographical location (Ellis 1997). In 
general, giant clams appear to have relatively late sexual maturity, a 
sessile, exposed adult phase and broadcast spawning reproductive 
strategy, all of which can make giant clams vulnerable to depletion and 
exploitation (Neo et al., 2015). All giant clam species are classified 
as protandrous functional hermaphrodites, meaning they mature first as 
males and develop later to function as both male and female (Chambers 
2007); but otherwise, giant clams follow the typical bivalve mollusc 
life cycle. At around 5 to 7 years of age (Kinch and Teitelbaum 2009), 
giant clams reproduce via broadcast spawning, in which several million 
sperm and eggs are released into the water column where fertilization 
takes place. Giant clam spawning can be seasonal; for example, in the 
Central Pacific, giant clams can spawn year round but are likely to 
have better gonad maturation around the new or full moon (Kinch and 
Teitelbaum 2009). In the Southern Pacific, giant clam spawning patterns 
are seasonal and clams are likely to spawn in spring and throughout the 
austral summer months (Kinch and Teitelbaum 2009). Once fertilized, the 
eggs hatch into free-swimming trochophore larvae for around 8 to 15 
days (according to the species and location) before settling on the 
substrate (Soo and Todd 2014; Kinch and Teitelbaum 2009). During the 
pediveliger larvae stage (the stage when the larvae is able to crawl 
using its foot), the larvae crawl on the substrate in search of 
suitable sites for settlement and metamorphose into early juveniles (or 
spats) within 2 weeks of spawning (Soo and Todd 2014). Growth rates 
after settlement generally follow a sigmoid (``S'' shaped) curve, 
beginning slowly, then accelerating after approximately 1 year and then 
slowing again as the animals approach maturity (Ellis 1997). These 
rates are usually slow and vary amongst species.

Feeding and Nutrition

    According to Munro (1992), giant clams are facultative 
planktotrophs, in that they are essentially planktotrophic (i.e., they 
feed on plankton) but they can acquire all of the nutrition required 
for maintenance from their symbiotic algae,

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Symbodinium. Nutritional requirements and strategies vary significantly 
by species. For example, T. derasa is able to function as a complete 
autotroph in its natural habitat (down to 20 m), whereas T. tevoroa 
only achieves this in the shallower parts of its distribution (10 to 20 
m). Tridacna gigas shows a different strategy, comfortably satisfying 
all apparent carbon requirements from the combined sources of filter-
feeding and phototrophy (Klumpp and Lucas 1994). In fact, Klumpp et al. 
(1992) showed that T. gigas is an efficient filter-feeder and that 
carbon derived from filter-feeding in Great Barrier Reef waters 
supplies significant amounts of the total carbon necessary for its 
respiration and growth.

Giant Clam Status and Abundance Trends

    The petition does not provide historical or current global 
abundance estimates for any of the petitioned clam species; rather, the 
petition cites a number of studies that document local extirpations of 
various giant clam species in particular areas to demonstrate that all 
species of giant clams are currently declining, or have declined 
historically, within their ranges. We assess the information presented 
in the petition, and information in our files, regarding each of the 
petitioned species in individual species accounts later in this 
finding.

ESA Section 4(a)(1) Factors

    The petition indicates that giant clam species merit listing due to 
all five ESA section 4(a)(1) factors: Present or threatened 
destruction, modification, or curtailment of its habitat or range; 
overutilization for commercial, recreational, scientific, or 
educational purposes; disease or predation; inadequacy of existing 
regulatory mechanisms; and other natural or manmade factors affecting 
its continued existence. We first discuss each of these threats to 
giant clams in general, and then discuss these threats as they relate 
to each species, based on information in the petition and the 
information readily available in our files.

Threats to Giant Clams

Present or Threatened Destruction, Modification, or Curtailment of Its 
Habitat or Range
    The petition contends that all giant clam species are at risk of 
extinction due to habitat destruction. The petitioner cites Foster and 
Vincent (2004) and states that: ``Giant clams inhabit shallow coastal 
waters which are highly vulnerable to habitat degradation caused by 
various anthropogenic activities.'' While we agree that highly 
populated coastal areas are subject to anthropogenic impacts (e.g., 
land-based sources of pollution, sedimentation, nutrient loading, 
etc.), the reference provided by the petitioner refers to habitat 
degradation as a threat to seahorse populations, with no information 
provided in this reference specific to giant clams. The petition also 
asserts that because giant clams are associated with coral reefs, that 
all species of giant clams face all of the ``regular'' threats that 
coral reefs generally face, including coral reef habitat degradation, 
sedimentation and pollution. The petition cites Brainard et al. (2011), 
a status review report that was prepared by NMFS for 82 coral species 
under the ESA, as evidence of habitat destruction issues throughout the 
range of the petitioned giant clam species. While this status review 
report thoroughly describes issues related to coral reef habitat 
degradation in general, it does not discuss giant clams, nor does it 
provide any substantial evidence regarding a link between coral reef 
habitat degradation and negative population-level impacts to any of the 
petitioned giant clam species throughout their ranges. Further, the 
petition itself notes that while giant clam species are generally 
associated with coral reefs, it is not an obligate relationship. In 
fact, surveys in many areas suggest that adults of most species of 
giant clams can live in most of the habitats available in coralline 
tropical seas (Munro 1992), with observations of giant clam species 
inhabiting a diverse variety of habitats (e.g., live coral, dead 
encrusted coral, coral rubble, seagrass beds, sandy substrates, 
boulders, macroalgae zones, etc.; Gilbert et al., 2006; Hernawan 2010). 
Additionally, while the petition describes the ecological importance of 
giant clams to coral reefs, the petition does not provide any 
information demonstrating the importance of pristine coral reef habitat 
to the survival of giant clam species.
    Finally, the petitioner also notes evidence from the South China 
Sea that 40 square miles (104 sq km) of coral reefs have been destroyed 
as a result of giant clam poaching, with an additional 22 square miles 
(57 sq km) destroyed by island-building and dredging activities. The 
petitioner notes that the main target during these poaching activities 
is T. gigas, because its large shell is considered a desirable luxury 
item in mainland China. Although directed poaching of giant clams would 
fall under the threat of overutilization, the means of poaching (e.g., 
explosives, tools of various sorts, and/or dragging and pulling to 
remove giant clams from the surrounding habitat) clearly has impacts to 
coral reef habitat as well. However, it is unclear how the loss of 
coral reefs in the South China Sea may impact the status of giant clams 
throughout their ranges, and aside from T. gigas, the petition provides 
no species-specific information regarding habitat destruction for the 
other nine petitioned species.
    Therefore, while the information in the petition suggests concern 
for the status of coral reef habitat generally, its broadness, 
generality, and speculative nature, and the lack of connections between 
the threats discussed and the status of the giant clam species 
specifically, means that we cannot find that this information 
reasonably suggests that habitat destruction is an operative threat 
that acts or has acted on each of the species to the point that they 
may warrant protection under the ESA. Broad statements about 
generalized threats to the species, or identification of factors that 
could negatively impact a species, do not constitute substantial 
information that listing may be warranted. We look for information 
indicating that not only is the particular species exposed to a factor, 
but that the species may be responding in a negative fashion; then we 
assess the potential significance of that negative response and 
consider the significance within the context of the species' overall 
range. In this case, generalized evidence of declining coral reef 
habitat is not evidence of a significant threat to any of the 
individual petitioned species to infer extinction risk such that the 
species may meet the definition of either threatened or endangered 
under the ESA.
    In addition to habitat degradation as a result of various 
anthropogenic activities, the petition contends that climate change 
related threats, including ocean warming and ocean acidification, are 
operative threats to all giant clam species and the coral reef habitat 
they rely on. The petitioner cites Brainard et al. (2011) and NMFS' 
proposed and final rules to list numerous reef-building corals under 
the ESA (77 FR 73219; December 7, 2012 and 79 FR 53852; September 10, 
2014) as substantial information to support these claims. While we 
agree with the petitioner that coral bleaching events have been 
increasing in both intensity and geographic extent because of climate 
change, and the information in the petition suggests concern for coral 
reef ecosystems, we disagree with the petitioner's broad and 
generalized

[[Page 28950]]

application of this information to the status of giant clams.
    With regard to climate change related threats to coral reef 
habitat, NMFS' final rule to list 20 species of reef-building corals 
(79 FR 53852; September 10, 2014) explains that exposure and response 
of coral species to global threats varies spatially and temporally, 
based on variability in the species' habitat and distribution. The vast 
majority of coral species occur across multiple habitat types, or reef 
environments, and have distributions that encompass diverse physical 
environmental conditions that influence how that species responds to 
global threats. Additionally, the best available information, as 
summarized in Brainard et al. (2011) and the coral final rule (79 FR 
53852; September 10, 2014), shows that adaptation and acclimatization 
to increased ocean temperatures are possible; there is intra-genus 
variation in susceptibility to bleaching, ocean acidification, and 
sedimentation; at least some coral species have already expanded their 
ranges in response to climate change; and not all species are seriously 
affected by ocean acidification. In fact, some studies suggest that 
coral reef degradation resulting from global climate change threats 
alone is likely to be an extremely spatially, temporally, and 
taxonomically heterogeneous process. These studies indicate that coral 
reef ecosystems, rather than disappear entirely as a result of future 
impacts, will likely persist, but with unpredictable changes in the 
composition of coral species and ecological functions (Hughes et al., 
2012; Pandolfi et al., 2011). We have additional information regarding 
climate change impacts and predictions for coral reefs readily 
available in our files, which indicates a highly nuanced and variable 
pattern of exposure, susceptibility, resilience, and recovery over 
regionally and locally different spatial and temporal scales, with much 
uncertainty remaining. The literature underscores the multitude of 
factors contributing to coral response to thermal stress, including 
taxa, geographic location, biomass, previous exposure, frequency, 
intensity, and duration of thermal stress events, gene expression, and 
symbiotic relationships (Pandolfi et al., 2011; Putman et al., 2011; 
Buddemeier et al., 2012; Sridhar et al., 2012; Teneva et al., 2012; van 
Hooidonk and Huber, 2012). Evidence suggests that coral bleaching 
events will continue to occur and become more severe and more frequent 
over the next few decades (van Hooidonk 2013). However, newer 
multivariate modeling approaches indicate that traditional temperature 
threshold models may not give an accurate picture of the likely 
outcomes of climate change for coral reefs, and effects and responses 
will be highly nuanced and heterogeneous across space and time 
(McClanahan et al., 2015).
    In addition to bleaching, the petitioner similarly implies that 
ocean acidification is a threat to giant clam habitat (i.e., corals and 
coral reefs). The petition cites Brainard et al. (2011) and states: 
``ocean acidification threatens to slow or halt coral growth and reef 
building entirely if the pH of the ocean becomes too low for corals to 
form their calcite skeletons.'' The petition further states that 
bioerosion of coral reefs is likely to accelerate as skeletons become 
more fragile because of the effects of acidification. However, aside 
from these broad and generalized statements regarding the potential 
impacts of ocean acidification to giant clam habitat (based largely on 
information regarding ocean acidification impacts to corals and coral 
reefs), the petition provides very limited information regarding 
species-specific impacts of ocean acidification for most of the 
petitioned giant clam species. Additionally, as with coral bleaching, 
Brainard et al. (2011) and the coral final rule (79 FR 53852; September 
10, 2014) show that adaptation and acclimatization to ocean 
acidification are possible, there is intra-genus variation in 
susceptibility to ocean acidification, and not all species are 
seriously affected. The previous discussion regarding spatial and 
temporal variability regarding how coral species respond to increasing 
temperature also applies to how corals respond to impacts of ocean 
acidification. Despite the generally high-ranking global threats from 
climate change, including coral bleaching and acidification and 
considerations of how these threats may act synergistically, only 20 of 
the 83 petitioned coral species ultimately warranted listing under the 
ESA. This underscores the fact that reef-building corals exist within a 
wide spectrum of susceptibility and vulnerability to global climate 
change threats. Thus, at the broad level of coral reefs, the 
information in the petition and in our files does not allow us to 
conclude that coral reefs generally are at such risk from ocean 
acidification effects as to threaten the viability of the petitioned 
giant clam species.
    Finally, the petition provided no information or analysis regarding 
how changes in coral reef composition and function because of climate 
change pose an extinction risk to any of the petitioned giant clam 
species. This is particularly important given that giant clams do not 
have an obligate relationship to coral reefs and, like corals, occur in 
a wide variety of habitats that encompass diverse physical 
environmental conditions that influence how a particular species 
responds to global threats. Broad generalizations regarding climate 
change related threats and their impacts cannot be applied as an 
equivalent threat to corals and coral reef associated species. In cases 
where the petitioner provided relevant species-specific information 
regarding climate change impacts, we consider this information in 
further detail below in the individual species accounts.
Overutilization for Commercial, Recreational, Scientific, or 
Educational Purposes
    The petition describes several activities that may be contributing 
to the overutilization of giant clams in general. The petition notes 
that harvest of giant clams is for both subsistence purposes (e.g., 
giant clam adductor, gonad, muscle, and mantle tissues are all used for 
food products and local consumption), as well as commercial purposes 
for global international trade (e.g., giant clam shells are used for a 
number of items, including jewelry, ornaments, soap dishes).
    The petition discusses a number of commercial fisheries that 
operated historically, including long-range Taiwanese fishing vessels 
and some local fisheries that developed in the 1970s and 1980s (e.g., 
Papua New Guinea, Fiji, Maldives). According to Munro (1992), 
historical commercial fisheries appear to have been limited to long-
range Taiwanese fishing vessels, which targeted the adductor muscles of 
larger species (e.g., T. gigas and T. derasa). This activity reached 
its peak in the mid-1970s and then subsided in the face of depleted 
stocks, strong international pressures, and improved surveillance of 
reef areas (Munro 1992). In response to declining activities by the 
Taiwanese fishery and continuing demand for giant clam meat, commercial 
fisheries developed in Papua New Guinea, Fiji, and the Maldives. For 
example, the Fijian fishery, which was exclusively for T. derasa, 
landed over 218 tons over a 9-year period, with the largest annual 
harvest totaling 49.5 tons in 1984. The petition cites Lewis et al. 
(1998) in stating this level of harvest is ``thought to have removed 
most of the available stock,'' but the authors actually stated that in 
1984-85 there were still abundant populations on various reefs in the 
windward (Lau, Lomaiviti)

[[Page 28951]]

islands but subsequent commercial harvest has considerably reduced 
these numbers. Because of these rapidly depleting local stocks, 
government authorities closed the fisheries (Munro 1992). The petition 
also noted historical commercial overutilization of giant clams (i.e., 
T. gigas and T. derasa) in Palau. Hester and Jones (1974) recorded 
densities of 50 T. gigas and 33 T. derasa per hectare at Helen Reef, 
Palau, before these stocks were ``totally decimated by distant-water 
fishing vessels'' (Munro 1992), although no further information or 
citations are provided to better describe the decimation. The petition 
discusses a few other studies that document historical overutilization 
of giant clams in various locations, including Japan, Philippines, 
Malaysia, and Micronesia (Okada 1997; Villanoy et al., 1988; Tan and 
Yasin 2003; and Lucas 1994, respectively). Thus, it is clear that in 
some locations, giant clams, particularly the largest species (T. gigas 
and T. derasa), have likely experienced historical overutilization as a 
result of commercial harvest. However, it should be noted that the 
large majority of the information provided in the petition points to 
selective targeting of the largest giant clam species, with limited 
information on many of the other petitioned giant clam species. 
Therefore, we cannot conclude that overutilization is contributing 
equally or to the same extent to the extinction risk of all giant clam 
species. Thus, any individual studies and species-specific information 
are discussed and analyzed in further detail in the individual species 
accounts below.
    In terms of current and ongoing threats of overutilization to giant 
clams, the petition emphasizes the threat of the growing giant clam 
industry in China, largely the result of improved carving techniques, 
increased tourism in Hainan, China, the growth in e-commerce, and the 
domestic Chinese wholesale market (Larson 2016). The petition also 
cites McManus (2016) to note concerns that stricter enforcement of the 
trade in ivory products has diverted attention to giant clam shells. 
The petition points out that the giant clam (T. gigas) is the main 
target for international trade, as this species' shell is considered a 
desirable luxury item, with a pair of high quality shells (from one 
individual) selling for upwards of US $150,000. Therefore, the high 
value and demand for large T. gigas shells may be a driving factor 
contributing to ongoing overutilization of the species. However, aside 
from T. gigas, the petition provides very limited information regarding 
the threat of international trade to the other nine petitioned giant 
clam species. Based on the information presented in the petition and in 
our files, we acknowledge that international trade may be a threat to 
some species (e.g., T. gigas), but we cannot conclude that 
international trade is posing an equivalent threat to all of the 
petitioned species, as it is clear that some giant clam species are 
more desirable and targeted more for international trade than others. A 
more detailed analysis of available species-specific trade information 
presented in the petition and in our files can be found in the 
individual species accounts in later sections of this notice.
    Although the petition does not mention aquaculture and hatchery 
programs, we found some information in our files on numerous giant clam 
aquaculture and hatchery programs throughout the Indo-Pacific, with 
several species being cultured in captivity for the purpose of 
international trade and restocking/reseeding programs to enhance wild 
populations. Currently, a variety of hatchery and nursery production 
systems are being utilized in over 21 Indo-Pacific countries 
(Teitelbaum and Friedman 2008), with several Pacific Island Countries 
and Territories (PICTs) across the Pacific using giant clam aquaculture 
and restocking programs to help enhance wild populations and culture 
clams for commercial use/trade. For example, the Cook Islands cultures 
giant clams at the Aitutaki Marine Research Center and exported 30,000 
giant clams from 2003 to 2006 for the global marine aquarium trade 
(Kinch and Teitelbaum 2009). In 2005, the Palau National Government 
established the Palau Maricultural Demonstration Center Program to 
conduct research on giant clam culture and to establish community-based 
giant clam grow-out farms. This program has helped establish 46 giant 
clam farms throughout Palau, with over two million giant clam 
`seedlings' distributed (Kinch and Teitelbaum 2009). At least 10 
percent of all giant clams from each farm are also kept aside to spawn 
naturally in their own ranched enclosures, thus reseeding nearby areas. 
In addition to being used to reseed areas in Palau, the program 
exported approximately 10,000 cultured giant clams each year from 2005 
to 2008 to France, Germany, Canada, the United States (including Guam 
and the Federated States of Micronesia (FSM)), Korea, and Taiwan. Other 
major producers of cultured giant clams for export include the Republic 
of the Marshall Islands, Tonga, and the FSM, producing an approximate 
average of 15-20,000 pieces of clams per year (Kinch and Teitelbaum 
2009). Therefore, the international trade of giant clams is complex, 
with many facets to consider, including the increasing influx of 
cultured giant clams into the trade. We acknowledge that the success of 
these restocking programs have been variable and limited in some 
locations (Teitelbaum and Friedman 2008); however, given the foregoing 
information, we cannot conclude that international trade poses an equal 
extinction risk to all of the petitioned giant clam species. In cases 
where the petition did provide species-specific information regarding 
commercial trade, we consider this information, as well as what is in 
our files, in the individual species accounts below.
Disease and Predation
    The petition states that predation is not likely a threat to giant 
clam species, as there is no evidence to suggest that levels of 
predation have changed or are unnaturally high and affecting the status 
of giant clam populations. We could also find no additional information 
in our files regarding the threat of predation for any of the 
petitioned clam species.
    The petition asserts that because diseases have been documented in 
a number of species and have likely increased in concert with climate 
change, they cannot be ruled out as a threat. The petition presented 
some limited information on diseases (e.g., impacts of protozoans and 
parasitic gastropods on giant clams and other bivalves on the Great 
Barrier Reef of Australia), but did not provide any species-specific 
information regarding how diseases may be impacting giant clam 
populations to the point that disease poses an extinction risk to any 
of the petitioned clam species. We could also not find any additional 
information in our files regarding the threat of disease for any of the 
petitioned clam species. Therefore, we conclude that the petition does 
not provide substantial information that disease or predation is a 
threat contributing to any of the species' risk of extinction, such 
that it is cause for concern.

Inadequacy of Existing Regulatory Mechanisms

    The petition claims existing regulatory mechanisms at the 
international, federal, and state level to protect giant clams or the 
habitat they need to survive are inadequate. The petitioner asserts 
that not only are local and national laws inadequate to protect

[[Page 28952]]

giant clams, but that international trade and greenhouse gas 
regulations are also inadequate. We address each of these topics 
separately below.
Local and National Giant Clam Regulations
    The petitioner notes that there are some laws for giant clams on 
the books in certain locations, but only discusses regulations from the 
Philippines and Malaysia and a separate issue of illegal clam poaching 
in disputed areas of the South China Sea. The petition acknowledges 
that all species of giant clam in the Philippines are protected as 
endangered species under the Philippine's Fisheries Administrative 
Order No. 208 series of 2001 (Dolorosa and Schoppe 2005), but states 
that despite this law, declines of giant clams continue. However, the 
only study presented on abundance trends since the law was implemented 
in 2001 was conducted on one reef (Tubbataha Reef; Dolorosa and Schoppe 
2005). Dolorosa and Schoppe (2005) specifically stated that they could 
not conclude a continuous decline of tridacnids was occurring because 
the much lower density observed in their study was based on data taken 
from a single transect. Prior to the study conducted by Dolorosa and 
Schoppe (2005), the only quantitative information presented was from 
studies conducted in the 1980s and 1990s (Villanoy et al., 1988; 
Salazar et al., 1999). Therefore, based on the foregoing information, 
we cannot conclude that the aforementioned fisheries law is inadequate 
for mitigating local threats to giant clams and slowing or halting 
population declines in the Philippines. However, illegal poaching for 
some species does seem to be an issue in some areas of the Philippines, 
notably in the protected area of Tubbataha Reef National Marine Park. 
For example, hundreds of giant clams (T. gigas) were confiscated from 
Chinese fishermen who poached in the Park in the early 2000s (Dolorossa 
and Schoppe 2005), indicating that regulatory mechanisms (e.g., the 
protected area) may not be adequate to protect that highly sought after 
species.
    The petitioner also notes that Malaysia's Department of Fisheries 
has listed giant clams as protected species, but cites Tan and Yasin 
(2003) as evidence that giant clams continue to decline despite this 
protective regulation. The petition provides no details regarding when 
this law was implemented or what specific protections it affords giant 
clams in Malaysian waters, nor could we find these details in the 
reference provided (Tan and Yasin 2003). Given that Malaysia represents 
a different proportion of each of the petitioned species' overall 
range, the potential inadequacy of regulatory mechanisms in Malaysia 
will be assessed and considered for each of the petitioned species in 
the individual species accounts below.
    Overall, the discussion of inadequate regulatory mechanisms for 
giant clams at the national/local level by the petitioner focuses on 
Southeast Asia, without any information regarding regulatory mechanisms 
throughout large portions of the rest of the ranges of the species. 
However, we found regulations in our files in numerous countries 
throughout the tropical Pacific (e.g., PICTs) and Australia regarding 
the harvest of giant clams. For example, size limits and complete bans 
on commercial harvest are the most commonly used fisheries management 
tools for giant clams throughout the PICTs (Kinch and Teitelbaum 2009). 
Several countries, including French Polynesia, Niue, Samoa, and Tonga, 
have size limits imposed for certain species. Some PICTs, such as Fiji 
and New Caledonia, both of which have active high volume tourist 
trades, allow up to three giant clam shells (or six halves) not 
weighing more than 3 kg to be exported with Convention on International 
Trade of Endangered Species of Wild Fauna and Flora (CITES) permits. 
Other PICTs, such as Guam and New Caledonia, have imposed bag-limits on 
subsistence and commercial harvest of giant clams. Papua New Guinea has 
imposed a ban on the use of night lights to harvest giant clams. There 
are also community-based cultural management systems in many PICTs like 
the Cook Islands where a local village or villages may institute rahui, 
or closed areas, for a period of time to allow stocks to recover 
(Chambers 2007). Finally, the following PICTs have complete bans on 
commercial harvest and export, with the exception of aquacultured 
species: FSM, Fiji, French Polynesia, Kiribati, Palau, Solomon Islands, 
and Vanuatu (Kinch and Teitelbaum 2009). Therefore, without any 
information or analysis as to how these regulatory measures are failing 
to address local threats to giant clams, we cannot conclude that there 
is substantial information indicating that regulatory mechanisms for 
all of the petitioned giant clam species are equally inadequate such 
that they may be posing an extinction risk to the species. Where more 
specific information is available for a particular species, we consider 
this information in the individual species accounts later in this 
finding.
Trade Regulations
    The petition asserts that international regulations, specifically 
the CITES, are inadequate to control commercial trade of giant clam 
species. The petition explains that although all members of the 
Tridacninae family are listed under Appendix II of CITES, 
implementation and enforcement are likely not adequate and thus illegal 
shipments are not necessarily intercepted. However, the assertions 
regarding illegal shipments were made broadly about wildlife shipments 
in general, without providing any specific information or clear 
linkages regarding how CITES is failing to regulate international trade 
of each of the petitioned giant clam species. The petition cites a 
number of CITES documents and states that these documents ``show wide 
disparities in yearly giant clam trade figures,'' which suggest that 
some countries have failed to exert control on the clam trade (bin 
Othman et al., 2010). However, the petition did not provide any 
additional details explaining how these trade figures demonstrate a 
risk of extinction to any particular species.
    Overall, the discussion of the inadequacy of CITES is very broad 
and does not discuss how the inadequacy of international trade 
regulations is impacting any of the petitioned species to the point 
that it is contributing to an extinction risk, with the exception of T. 
gigas and the growing giant clam industry in China. For example, the 
petition points out that the shape of the large giant clam shells (T. 
gigas) makes them highly desirable for making large, intricately carved 
scenes. In fact, the petition itself emphasizes that T. gigas is the 
main giant clam species targeted and poached in the South China Sea for 
this particular trade. Therefore, from the information in the petition 
and our files, it is clear that some giant clam species are more 
desirable and targeted for the international trade than others, and 
thus require more restrictive regulations to ensure their 
sustainability. As discussed previously in the Overutilization for 
Commercial, Recreational, Scientific, or Educational section above, we 
concluded that, for giant clams in general, the information in the 
petition and our files does not constitute substantial information that 
international trade is posing an equivalent threat to all of the 
petitioned giant clam species. Therefore, while we acknowledge that 
international trade may be a threat to some species, and existing 
regulations may be inadequate and warrant further investigation, the 
assertion that inadequate regulations for international trade is an 
equivalent

[[Page 28953]]

threat to all of the petitioned giant clam species is not supported.
Greenhouse Gas Regulations
    The petition claims that regulatory mechanisms to curb greenhouse 
gas emissions and reduce the effects of global climate change are 
inadequate to protect giant clams from the threats climate change poses 
to the species and their habitat. The petition goes on to explain that 
climate change threats, including bleaching and ocean acidification, 
represent the most significant long-term threat to the future of global 
biodiversity. Information in our files and from scientific literature 
indeed indicates that greenhouse gas emissions have a negative impact 
to reef building corals (NMFS 2012). However, as we discussed in detail 
previously, beyond this generalized global threat to coral reefs, we do 
not find that the petition presents substantial information indicating 
that the effects of greenhouse gas emissions are negatively affecting 
the petitioned species or their habitat such that they may warrant 
listing under the ESA. In particular, the information in the petition 
and in our files does not indicate that the loss of coral reef habitat 
or the direct effects of ocean warming and acidification is 
contributing to the extinction risk of the petitioned species (refer 
back to the Present or Threatened Destruction, Modification or 
Curtailment of its Habitat or Range section above and the Other Natural 
or Manmade Factors section below). Therefore, with the exception of 
species for which species-specific information is available regarding 
negative responses to ocean warming or acidification, inadequate 
regulatory mechanisms controlling greenhouse gas emissions are not 
considered a factor that may be contributing to the extinction risk of 
the petitioned species.

Other Natural or Manmade Factors Affecting Its Continued Existence

Ocean Warming and Giant Clam Bleaching
    The petitioner discusses the climate change-related impacts of 
ocean warming and giant clam bleaching as an extinction risk to all the 
petitioned giant clam species. In terms of giant clam bleaching, the 
petitioner argues that giant clams are like stony corals, in that the 
Symbodinium zooxanthellae in giant clams are subject to bleaching and 
other effects from high temperature. The petitioner provides a number 
of studies documenting giant clam bleaching in various locations, 
including the Great Barrier Reef in Australia and Southeast Asia. The 
petition then describes several studies on the physiological effects to 
giant clams from bleaching and ocean acidification, with the large 
majority of these studies conducted on T. gigas. However, while the 
petition provides some evidence that giant clams experience bleaching 
as a result of increased temperature, there is no discussion regarding 
how giant clams tolerate bleaching or the extent to which bleaching 
leads to mortality for the majority of the petitioned species. For 
example, the petition discusses a study by Leggat et al. (2003), in 
which the symbiotic zooxanthellae in T. gigas declined 30-fold during 
the 1998 global coral bleaching event, leading to a loss of the 
nutrition provided by zooxanthellae in ways very similar to the effects 
on stony corals; however, the petition failed to present any discussion 
or analysis as to how this stressor is linked to mortality of giant 
clams or population declines. In fact, the main conclusion of the 
Leggat et al. (2003) study states:

    Despite this significant reduction in symbiont population, and 
the consequent changes to their carbon and nitrogen budgets, the 
clams are able to cope with bleaching events significantly better 
than corals. During the recovery of clams after an artificial 
bleaching event only three out of 24 clams died, and personal 
observations at Orpheus Island indicated that survival rates of 
bleached clams were greater than 95 percent under natural 
conditions. This is in contrast to reports indicating coral 
mortality in some species can be as great as 99 percent.

    Therefore, although giant clams and stony corals can experience 
similar bleaching of their symbiotic zooxanthellae, this does not 
necessarily equate to analogous impacts of widespread bleaching-induced 
mortality from ocean warming. As discussed for another reef-dwelling 
organism in the orange clownfish 12-month finding (80 FR 51235), 
anemones also have symbiotic zooxanthellae, but literature on the 
effects of ocean warming on anemones show results that are not 
necessarily analogous with corals either, and in fact show high 
variability between and within species. Even individual anemones can 
show varying responses across different bleaching events. Although 
observed anemone bleaching has thus far been highly variable during 
localized events, the overall effect of bleaching events on anemones 
globally (i.e., overall proportion of observed anemones that have shown 
ill effects) has been of low magnitude at sites across their ranges. In 
fact, only 3.5 percent of the nearly 14,000 observed anemones were 
recorded as bleached across 19 study sites and multiple major bleaching 
events (Hobbs et al., 2013). Based on this example, generalized 
statements about bleaching impacts to all organisms that have symbiotic 
dinoflagellates being analogous are not supported by the best available 
information.
    Without species-specific information on how ocean warming-induced 
bleaching affects each of the petitioned giant clam species (e.g., 
mortality rates and evidence of negative population level effects), we 
cannot conclude that bleaching caused by ocean warming may be acting 
equally on all of the petitioned species to the point that the 
petitioned action may be warranted. Where the petition provides some 
species-specific information regarding the effects of temperature-
induced bleaching, we consider this information in more detail in the 
individual species accounts below.
Ocean Acidification
    Similar to the effects of ocean warming, the petitioner discusses 
ocean acidification as a threat contributing to the extinction risk of 
all of the petitioned giant clam species. The petitioner asserts that 
the effects of ocean acidification will likely accelerate the 
bioerosion of giant clam shells and lead to their increased fragility. 
To support this assertion, the petition cites two studies. One study 
(Waters 2008) looked at cultured specimens of T. maxima in a lab 
experiment and found that T. maxima juveniles exposed to 
pCO2 concentrations approximating glacial (180 ppm), current 
(380 ppm) and projected (560 ppm and 840 ppm) levels of atmospheric 
CO2 (per the IPCC IS92a scenario) suffered decreases in size 
and dissolution, and this occurred below thresholds previously 
considered detrimental to other marine organisms in similar conditions. 
We discuss these results and implications in further detail in the T. 
maxima species account below.
    The second study (Lin et al., 2006) did not specifically evaluate 
impacts of ocean acidification but instead involved mechanical tests on 
the shells of conch (Strombus gigas), giant clam (T. gigas), and red 
abalone (Haliotis rufescens) for a comparison of strength with respect 
to the microstructural architecture and sample orientation. The study 
found that although the structure of the T. gigas shell had the lowest 
level of organization of the three shells, its sheer size results in a 
strong overall system (Lin et al., 2006). The petitioner claims that 
because T. gigas has the lowest flexural shell strength relative to the 
two other types of shells tested, that any loss

[[Page 28954]]

of shell material or strength from the effects of ocean acidification 
may have a greater negative effect on giant clams than on other large 
molluscs. However, this statement is speculative, and no additional 
information or references were provided to support this claim.
    Overall, while we agree that ocean acidification is likely to 
continue and increase in severity over time within the ranges of the 
giant clam species, resulting in various detrimental impacts, 
additional information in our files also underscores the complexity and 
uncertainty associated with the various specific effects of ocean 
acidification across the ranges of giant clams. There are numerous 
complex spatial and temporal factors that compound uncertainty 
associated with projecting effects of ocean acidification on coral reef 
associated species such as giant clams. Further, as explained in the 
final rule to list 20 reef-building coral species under the ESA (79 FR 
53852; September 10, 2014), projecting species-specific responses to 
global threats is complicated by several physical and biological 
factors that also apply to the petitioned giant clam species. First, 
global projections of changes to ocean acidification into the future 
are associated with three major sources of uncertainty, including 
greenhouse gas emissions assumptions, strength of the climate's 
response to greenhouse gas concentrations, and large natural 
variations. There is also spatial and temporal variability in projected 
environmental conditions across the ranges of the species. Finally, 
species-specific responses depend on numerous biological 
characteristics, including (at a minimum) distribution, abundance, life 
history, susceptibility to threats, and capacity for acclimatization.
    In this case, the petition did not provide sufficient information 
regarding the likely impacts of ocean acidification on specific giant 
clam species or their populations. Without any analysis of how ocean 
acidification may be negatively impacting each of the petitioned giant 
clam species (with the exception of T. maxima and T. squamosa), we 
cannot conclude that substantial information was provided to indicate 
effects of ocean acidification may be acting on all of the petitioned 
species to the point that the petitioned action may be warranted. In 
cases where the petition did provide species-specific information, we 
consider this information in further detail in the individual species 
accounts below.

Individual Species Accounts

    Based on the information presented in the petition and in our 
files, we made 10 separate 90-day findings, one for each of the 
petitioned giant clam species. We first address the seven species for 
which we have determined that the information presented in the petition 
and in our files constitutes substantial information that the 
petitioned action may be warranted (i.e., positive 90-day finding). 
Because we will be addressing all potential threats to these species in 
forthcoming status reviews, we will only provide summaries of the main 
threat information in these species accounts as opposed to addressing 
every ESA (4)(a)(1) factor. Then, we address the remaining three 
species for which we determined that the information presented in the 
petition and in our files does not constitute substantial information 
that the petitioned action is warranted (i.e., negative 90-day 
finding). In these species accounts, we address every ESA (4)(a)(1) 
factor individually.

Hippopus hippopus

Species Description
    The petition does not provide any descriptive information for H. 
hippopus. We found some information in our files describing this 
species. Its shell exterior is off-white with a yellowish orange 
coloring and reddish blotches arranged in irregular concentric bands; 
the shell interior is porcelaneous white, frequently flushed with 
yellowish orange on the ventral margin, and the mantle ranges from a 
yellowish-brown, dull green, or grey (Kinch and Teitelbaum 2009). 
Maximum shell length for H. hippopus is 40 cm, but it is commonly found 
at lengths up to 20 cm. It can be found on sandy bottoms of coral reefs 
in shallow water to a depth of 6 m. Smaller specimens (up to about 15 
cm in length) are often attached to coral rubble by their byssal 
strings, while large and heavy specimens are unattached and lack a 
byssus (Kinch and Teitelbaum 2009).
Life History
    The petitioner provides some information on life history specific 
to this species. He cites Shelley (1989) who found second sexual 
maturity in H. hippopus at Orpheus Island, Great Barrier Reef, at a 
shell size of 145mm which equated to 2 years of age for males and 4 
years of age for hermaphrodites of the species from the study area. He 
cites Stephenson (1934) and Shelley (1989) who reported that H. 
hippopus spawns in the austral summer months of December to March on 
the Great Barrier Reef, which is also supported by Munro (1992) who 
found spawning of H. hippopus to be restricted to a short summer season 
in the central region of the Great Barrier Reef. In Palau, Hardy and 
Hardy (1969) reported that H. hippopus spawned in June. In a detailed 
study of early life history in Guam, fertilized eggs of H. hippopus had 
a mean diameter of 130.0 [mu]m (micrometers; 13 cm; Jameson 1976). 
According to the same study, settlement in Guam occurred 9 days after 
fertilization at a mean shell length of 202.0 [mu]m (20.2 cm) for H. 
hippopus. Juveniles of H. hippopus in Guam first acquired zooxanthellae 
after 25 days and juvenile shells showed first signs of becoming opaque 
after 50 days (Jameson 1976).
Range, Habitat, and Distribution
    The petition includes a range map for H. hippopus that was 
excerpted from bin Othman et al. (2010). bin Othman et al. (2010) note 
that data from Reef Check (www.reefcheck.org) indicate that there are 
populations of giant clams beyond the species-specific boundaries 
described by the references on which the range maps within bin Othman 
et al. (2010) are based, although no further detail is provided for any 
species. This applies to all species for which range maps based on bin 
Othman et al. (2010) are provided in this finding. The range map for H. 
hippopus provided in the petition does include several U.S. Pacific 
areas including Guam, Commonwealth of the Northern Mariana Islands 
(CNMI), and Wake Atoll. According to the petition, H. hippopus also 
historically occurred in Singapore (Neo and Todd 2012b and 2013) and 
the United States, although locations in the United States are not 
specified and no reference is provided.

[[Page 28955]]

[GRAPHIC] [TIFF OMITTED] TP26JN17.000

    According to Munro (1992), H. hippopus occurs in the widest range 
of habitat types of all the Tridacninae species. This species is 
seemingly equally comfortable on sandy atoll lagoon floors or exposed 
intertidal habitats, and similar to T. gigas, which is found in many 
habitats (e.g., high or low islands, lagoons, or fringing reefs; Munro 
1992).
Population Status and Abundance Trends
    Although an overall population abundance estimate or population 
trends for H. hippopus are not presented, the petitioner does provide 
some limited abundance information from various locations within the 
species' range. For example, the petition cites Tan and Yasin (2003) 
who state that giant clams of all species but T. crocea are considered 
endangered in Malaysia. The authors mention underwater surveys that 
reveal the ``distribution of giant clams are widespread but their 
numbers are very low,'' but there are no references provided by the 
authors to provide any more detail or support for this information, 
which makes it difficult to interpret this information for individual 
species. The only species-specific information for H. hippopus in this 
reference is that it occurs in Malaysian waters. The petition states 
that Brown and Muskanofola (1985) found that H. hippopus was locally 
extinct in Indonesia. Upon review of this reference, more specifically, 
the authors found many small shells of H. hippopus but no living 
specimens in their survey area of seven island transects in Central 
Java, Indonesia. The authors noted that because of time constraints, it 
was not possible to cover more than a very small proportion of the 
total area suitable for clam growth in Karimun Jawa. Thus, confining 
the survey to such a small area could have affected the results. 
Hernawan (2010) found small populations and evidence of recruitment 
failure in the six species found during a survey of Kei Kecil, 
Southeast-Maluku, Indonesia, including H. hippopus. The authors 
conducted giant clam surveys in nine sites out of the many thousands of 
islands that make up Indonesia. At another site in Indonesia, Eliata et 
al. (2003) reported an 84 percent decline in H. hippopus based on 
surveys of Pari Island from 1984 and 2003. This species is presumed 
nationally extinct in Singapore (Neo and Todd 2012a, 2013) and has been 
reported as extirpated from Fiji, Tonga, Samoa and American Samoa, 
Guam, the Mariana Islands, and Taiwan (Wells 1996a, Skelton et al. 
2002, Teitelbaum and Friedman 2008).
    The petition presents three references from the Philippines on H. 
hippopus. Villanoy et al. (1988) states this species has been 
overexploited based on the export volumes of giant clam shells. The 
petitioner claims densities of H. hippopus declined by 97 percent in 
Tubbataha Reef Park in the Philippines from 1995-2005 based on a survey 
by Dolorosa and Schoppe (2005). However, upon closer review of this 
reference, the data in Dolorosa and Schoppe (2005) indicating a 
substantial decline in H. hippopus density was taken from a single 
transect; as such, the authors concluded that a continuous decline of 
the Tridacnids (including H. hippopus) could not be confirmed. Finally, 
Salazar et al. (1999) did a stock assessment of giant clams (including 
H. hippopus) in the Eastern Visayas of the Philippines and found most 
of the populations were made up of juveniles with insufficient numbers 
of breeders to repopulate the region, although this reference was 
unavailable for review. Notably, the petition cites Thamrongnavasawat 
(2001) as reporting that H. hippopus is considered extinct in Mo Ko 
Surin National Park in Thailand, although the bibliographic information 
provided for this reference did not allow us to access it for review.
    While individually and collectively the studies discussed in this 
section represent a small portion of H. hippopus' total geographic 
range, localized declines and potential extirpations of this species in 
small areas are spread throughout its range and not confined to one 
area that may be disproportionately affected by some negative impact. 
Thus, the number and spatial distribution of localized severe

[[Page 28956]]

declines or extirpations in the context of the species' range may be 
contributing to an elevated extinction risk for this species such that 
it warrants further investigation.
Threats to Hippopus hippopus
    The petition presents three studies with species-specific 
information regarding threats to H. hippopus. Some historical 
information indicates that shells of H. hippopus (long extirpated in 
Fiji) occur in shell middens at the Lapita-era (1100-550 B.C.) 
settlements (Bourewa and Qoqo) along the Rove Peninsula in Fiji; the 
valve size and weight increase with depth (i.e., age) in the midden, 
suggesting that human consumption contributed to its local 
disappearance (Seeto et al. 2012). While this one piece of evidence 
does not constitute substantial information that overharvest may be 
acting or may have acted on H. hippopus as a species to the extent that 
it needs protection under the ESA, the threat of overexploitation will 
be evaluated in the status review. Blidberg et al. (2000) studied the 
effect of increasing water temperature on T. gigas, T. derasa, and H. 
hippopus at a laboratory in the Philippines. Hippopus hippopus 
experienced increased respiration and production of oxygen in elevated 
temperatures and was therefore more sensitive to higher temperature 
than the two other species tested. After 24 hours at ambient 
temperature plus 3 [deg]C, however, no bleaching was observed for any 
of the species. While we acknowledge the potential for ocean warming to 
have an effect on this species, this was a limited experiment, the 
results of which are difficult to interpret in terms of the potential 
species-level or even localized impacts of physiological stress due to 
elevated ocean temperatures in the wild in the context of this 
assessment. While this one study does not constitute substantial 
information that climate change may be acting on H. hippopus as a 
species to the extent that it needs protection under the ESA, the 
impacts of ocean warming will be further evaluated for H. hippopus in 
the status review based on the best available information.
    Finally, Norton et al. (1993) found two incidences of mortality in 
H. hippopus from rickettsiales-like organisms in cultured clams in the 
western Pacific, one in the Philippines and one in Kosrae. However, it 
is not uncommon among individuals cultured in close proximity to be 
afflicted with parasites or diseases that spread quickly (Norton et 
al., 1993). While this does not constitute substantial information that 
disease or parasites may be acting on H. hippopus as a species to the 
extent it needs the protections of the ESA, the threats of disease and 
parasites will be further evaluated in a forthcoming status review.
Conclusion
    In conclusion, the information provided on threats for this species 
is limited and the individual studies by themselves are not substantial 
information indicating the petitioned action may be warranted for the 
species. However, the evidence presented of localized declines or 
extirpations in different parts of the species' range does suggest that 
one or more threats may be acting on the species throughout all or a 
significant portion of its range and the petitioned action may be 
warranted. The number and spatial distribution of localized severe 
declines or extirpations in the context of the species' range may be 
contributing to an elevated extinction risk for this species such that 
it warrants further investigation. The best available information on 
the species' overall status and all potential threats will be evaluated 
in a forthcoming status review to determine what has potentially caused 
these declines and extirpations.

Hippopus porcellanus

Species Description
    The petition does not provide any descriptive information for H. 
porcellanus. We found some information in our files describing this 
species. Commonly known as the China clam, H. porcellanus grows to a 
maximum of 40 cm, but is commonly found up to 20 cm in shell length. 
The shell exterior is off-white, occasionally with scattered weak 
reddish blotches. The shell interior is porcelaneous white, more or 
less flushed with orange on the ventral margin, and the mantle ranges 
from a yellowish-brown, dull green or grey (Kinch and Teitelbaum 2009). 
This species can be distinguished from its congener, H. hippopus, by 
its smoother and thinner shells and presence of fringing tentacles at 
its incurrent siphon (Neo et al., 2015).
Life History
    Aside from the information already discussed previously in the 
Giant Clam Life History section, the petition did not provide any life 
history information specific to H. porcellanus, nor could we find any 
additional information in our files on the life history of this 
species.
Range, Habitat, and Distribution
    Hippopus porcellanus has one of the most restricted geographic 
ranges of the petitioned giant clam species. The petition notes that 
the species only occurs in Palau, Indonesia, and the Philippines based 
on the IUCN assessment (Wells 1996); however, in the population 
abundance and trends section, the petition notes the endangered status 
of H. porcellanus in Malaysia, placing its occurrence there as well.

[[Page 28957]]

[GRAPHIC] [TIFF OMITTED] TP26JN17.001

    H. porcellanus can be found in shallow waters on sandy bottoms of 
coral reefs. Young specimens are often attached to coral heads via 
their byssus, whereas mature individuals lack a byssus and lay 
unattached on the substrate (Rosewater 1982).
Population Status and Abundance Trends
    The petition does not provide an overall population abundance or 
trend estimate for H. porcellanus as a species throughout its range. 
The petition does, however, provide limited, localized information on 
the population status and abundance trends of H. porcellanus, with some 
information from Malaysia and the Philippines, but no species-specific 
information from other parts of the species' range, including Indonesia 
and Palau. As discussed in other species accounts, the petitioner cites 
Tan and Yasin (2003), who state that giant clams of all species but T. 
crocea are considered endangered in Malaysia. As noted previously, the 
authors mention underwater surveys that reveal that the ``distribution 
of giant clams are widespread but their numbers are very low,'' but the 
authors do not provide any references with any more detail or support 
for this information, which makes it difficult to interpret this 
information for individual species. The only species-specific 
information for H. porcellanus in this reference is that it is 
restricted to Sabah, Eastern Malaysia.
    The petition asserts that H. porcellanus is overexploited and 
depleted in the Philippines based on Villanoy et al., (1988) and Rubec 
et al., (2001). Villanoy et al., (1988) examined average size frequency 
distributions of giant clams harvested from the Sulu Archipelago and 
Southern Palawan areas from 1978 to1985, and determined that H. 
porcellanus was overexploited in the Philippines as early as the 1980s. 
The authors note that these findings have serious implications given 
that the Sulu Archipelago and Southern Palawan may be the last 
strongholds of all giant clam species occurring in Philippine waters. 
Rubec et al. (2001) more recently described H. porcellanus as 
``depleted,'' but they did not provide any references or additional 
detail to help us determine what they meant by ``depleted'' or how this 
current information relates to historical abundance of the species in 
Philippine waters. Without any quantitative information on abundance 
trends of H. porcellanus in the Philippines since the 1980s, it is 
difficult to determine what the present status of the species is in 
this portion of its range. However, we note that because H. porcellanus 
has an extremely restricted geographic range, occurring in only three 
countries, overexploitation in the Philippines gives cause for concern 
and warrants further investigation.
    While H. porcellanus also occurs in Indonesia and Palau, the 
petition did not provide any additional information regarding the 
species' status or abundance trends in these locations. The information 
provided by the petitioner for giant clams in Indonesia is from a 
location where H. porcellanus is not known to occur (i.e., Kei Kecil, 
Indonesia). We could not otherwise find any information in our files 
from Indonesia or Palau regarding the status of H. porcellanus in these 
locations.
    Overall, while the information presented in the petition is very 
limited regarding the species' current status and abundance trends 
throughout its range and would not in and of itself constitute 
substantial information, the species' range is significantly 
restricted. Therefore, given that the species only occurs in four 
countries, the information presented in the petition from the 
Philippines, albeit limited, gives cause for concern that the species 
may have an elevated extinction risk that warrants further 
investigation.
Threats to H. porcellanus
    The only species-specific information provided by the petition 
regarding threats to H. porcellanus is related to overutilization in 
the Philippines. As described in the Population Status and Abundance 
Trends section above, the

[[Page 28958]]

petitioner cited Villanoy et al. (1988) as evidence of overutilization 
of H. porcellanus. Villanoy et al. (1988) notes that giant clams have 
long been harvested by subsistence fishermen in the Indo-Pacific Region 
as a supplementary source of protein. Additionally, in some areas of 
the Philippines (e.g. Sulu Archipelago, Southern Palawan), giant clams 
are also harvested commercially for their shells. After examining 
average size frequency distributions of giant clams harvested from the 
Sulu Archipelago and Southern Palawan areas from 1978-1985, Villanoy et 
al. (1988) determined that H. porcellanus was overexploited in the 
Philippines as early as the 1980s, and is no longer commercially 
harvested. As noted previously, the Sulu Archipelago and Southern 
Palawan areas are thought to be the last strongholds of giant clams in 
Philippine waters. Therefore, the overexploitation of H. porcellanus as 
of the 1980s and its restricted range could have serious implications 
regarding the species' extinction risk. More recently, Rubec et al. 
(2001) similarly document that H. porcellanus has been depleted to such 
an extent that it is no longer commercially viable for harvesting in 
the Philippines.
Conclusion
    In conclusion, the information provided on population abundance and 
threats for this species is limited and by itself would not be 
considered substantial information indicating the petitioned action may 
be warranted. The individual studies presented are not compelling 
evidence of species level concerns for reasons discussed above. 
However, given the species' extremely restricted range, combined with 
evidence of localized declines and historical overutilization in the 
Philippines, we find the information compelling enough to conclude that 
the petitioned action may be warranted. The best available information 
on the species' overall population status and all potential threats 
will be evaluated in a forthcoming status review.

Tridacna costata (T. squamosina)

Species Description
    Tridacna costata has been described only recently (Richter et al., 
2008; bin Othman et al., 2010), but it has been shown to be a junior 
synonym of the previously described T. squamosina (Borsa et al., 
2015a). This species of giant clam grows to 32 cm (Neo et al., 2015) 
and features 5-7 deep rib-like vertical folds, resulting in a zig-zag 
dorsal shell margin. According to Richter et al., (2008), the mantle is 
most commonly a subdued brown mottled pattern; mantle margins are green 
with prominent ``wart-like'' protrusions and pale striations following 
mantle contour. These features (the pronounced rib-like vertical folds 
and the prominent wart-like protrusions on the mantle tissue) are the 
main diagnostic features that separate T. costata from its sympatric 
congeners. These features are conservatively present even in small 
clams <10 cm shell length (Richter et al., 2008).
Life History
    The petition itself does not describe any species-specific life 
history information for T. costata, but we found some limited 
information in one of the references provided that suggests a narrow 
reproductive period. Richter et al. (2008) found marked differences in 
the seasonal times of reproduction between T. costata and its Red Sea 
congeners (T. maxima and T. squamosa). Specifically, T. costata's 
reproductive period appears to be an early and brief period in spring, 
coinciding with the seasonal planktonic bloom (Richter et al., 2008). 
This narrow reproductive window may make T. costata particularly 
vulnerable to overfishing. The timing of T. costata's reproduction 
combined with the small diameter of the ova (75 2 [SEM] 
[mu]m) suggests a planktotrophic (i.e., feeding on plankton) 
development of the larvae. This contrasts with the lecithotrophic 
(i.e., yolk-feeding) and hence food-independent larval development in 
the summer-spawning T. squamosa and T. maxima, which also have much 
larger eggs (35 percent 1 percent and 41 percent 2 percent by volume, respectively; Richter et al., 2008).
Range, Habitat, and Distribution
    Among giant clam species, T. costata has one of the most restricted 
geographical ranges, occurring only in the Red Sea. Richter et al. 
(2008) describes the species as occurring throughout the northeastern 
Gulf of Aqaba (type locality), Sinai coast, western Gulf of Aqaba, 
northern Red Sea, and Egyptian mainland down to Hurghada and Safaga.

[[Page 28959]]

[GRAPHIC] [TIFF OMITTED] TP26JN17.002

    In a survey of giant clams in the Red Sea, Richter et al. (2008) 
noted that live specimens of T. costata were found exclusively in very 
shallow water including reef flats, seagrass beds, sandy-rubble flats, 
on slight depressions in barren rocky flats, or under branching corals 
or coral heads shallower than 2m. All clams were weakly attached to the 
substrate. Thus, unlike its Red Sea congeners T. maxima and T. 
squamosa, which have broad vertical ranges of distribution, T. costata 
is restricted to the reef top (Richter et al., 2008).
Population Status and Abundance Trends
    Given the recent description of this species, information on its 
current population status and abundance trends is limited. However, one 
available study suggests a significant historical decline of the 
species. Results of surveys along the shores and well-dated emerged 
reef terraces of Sinai and Aqaba show that T. costata comprised >80 
percent of giant clam stocks prior to the last interglacial period 
(122,000 to 125,000 years ago). Subsequently, the proportion of T. 
costata plunged to <5 percent in freshly discarded shell middens 
(Richter et al., 2008). Currently, the species is thought to represent 
less than one percent of the present giant clam stocks in the Red Sea. 
For example, in underwater surveys conducted in the Gulf of Aqaba and 
northern Red Sea, only 6 out of 1,000 live specimens belonged to the 
new species, with densities averaging 0.9 0.4 individuals 
per 1,000 m\2\. The highest numbers for the species occurred on 
offshore shoals in the Red Sea proper; however, adult broodstock was 
below detection in much of the study area (Richter et al., 2008). In 
fact, only 13 live individuals of T. costata were observed along the 
entire Jordanian Red Sea coast, which prevented collection of paratypes 
(Richter et al., 2008).
Threats to T. costata
    Based on the limited information in the petition, we determined 
that historical and ongoing overutilization may be a threat 
contributing to an elevated extinction risk for this species that 
warrants further investigation, particularly given the species' 
restricted geographic range and shallow depth distribution. In general, 
Tridacna stocks in the Red Sea have declined to less than 5 percent of 
their sizes in the 1980s and 1990s, largely due to artisanal reef-top 
gathering for meat and shells (Richer et al., 2008). Richter et al. 
(2008) notes that modern humans have likely been exploiting Red Sea 
mollusks for at least 125,000 years. Although natural disturbances may 
be responsible for variable rates of recruitment and mortality among 
the three Red Sea giant clam species, the substantial reduction in 
Tridacna size (equivalent to ~20-fold decrease in individual body mass 
and fecundity accompanying the species shift) strongly indicates 
overfishing (Richter et al., 2008). Further, given that T. costata is 
restricted to the shallow reef top (and thus more accessible to reef 
top gathering), it is likely that overutilization of the species has 
contributed to its significant decline. Therefore, we conclude that the 
petition presents substantial information that overutilization may be a 
threat contributing to an elevated extinction risk for this particular 
species.
Conclusion
    Based on the above information, we find that the petition presents 
substantial scientific and commercial information indicating that the 
petitioned action of listing T. costata as threatened or endangered may 
be warranted. Its highly restricted range, reduced abundance, low 
productivity (due to its narrow reproductive periodicity), and the 
threat of overutilization for commercial purposes may be contributing 
to an elevated risk of extinction such that the petitioned action may 
be warranted. The best available information on the species' overall 
population status and all potential threats will be evaluated in a 
forthcoming status review.

Tridacna derasa

Species Description
    The petition itself does not provide any descriptive information 
for T. derasa. Neo et al. (2015) report that T. derasa is the second 
largest species, growing up to 60 cm with heavy and plain shells, with 
no strong ribbing. According to Lewis et al. (1998), the maximum size 
recorded in Fiji, 62 cm, is well above that recorded by

[[Page 28960]]

Rosewater (1965, 51.4 cm) who, however, had access to only few 
specimens. Specimens greater than 50 cm in length are relatively 
common.
Life History
    The petition presents very limited life history information for T. 
derasa. The optimal reproductive season for T. derasa sampled from 
Michaelmas Cay was from September/October to November/December (Braley 
1988). Simultaneous hermaphroditism was found in 0 to 28 percent of 
sampled T. derasa. We found no additional life history information for 
this species in our files.
Range, Habitat, and Distribution
    The petition does not provide a description of the geographic range 
for T. derasa, but it was included in the range map provided for most 
of the petitioned species. The map includes all of Malaysia, but Tan & 
Zulfigar (2003) report that T. derasa is restricted to Sabah, Eastern 
Malaysia. Wells (1996) noted that T. derasa has been introduced during 
various mariculture efforts in areas including the United States (e.g., 
Hawaii) and the Federated States of Micronesia. bin Othman et al. 
(2010) reports T. derasa from Australia, Palau, Papua New Guinea (PNG), 
and the Philippines. Tridacna derasa is noted as an introduced species 
in the Cook Islands and Samoa (introduced for aquaculture purposes) and 
also reported from Fiji, FSM, the Marshall Islands, New Caledonia, 
Solomon Islands, Tonga, and Vanuatu (CITES 2009).
[GRAPHIC] [TIFF OMITTED] TP26JN17.003

    Tridacna derasa preferentially inhabits clear offshore or oceanic 
waters away from high islands with significant run-off of freshwater 
(Munro 1992). For example, it is not recorded from the Papuan Barrier 
Reef running along the south coast of PNG, nor from the fringing reefs 
of the north coast, but it does occur within a few miles of the 
southeast point of mainland PNG (Munro 1992). Large T. derasa were also 
commonly found at 10 to 20 m depth in the clear oceanic conditions of 
the windward islands and barrier reefs of eastern Fiji (Adams et al., 
1988). Lewis et al. (1988) reported that:

    T. derasa has a curious NW-SE distribution across the Indo-
Malayan region, and is not found east of Tonga or in equatorial 
areas east of Solomon Islands. In Fiji, the species is generally 
confined to clear oceanic outer lagoon areas, within the protection 
of well-developed barrier or fringing reefs. Occurring near the 
surface down to 25 m, T. derasa occurs in greatest density in the 
windward (eastern) islands of the Fiji group. Very high numbers 
(hundreds/hectare) are occasionally noted. It is rare or absent from 
high island fringing reefs and lagoons where salinity and water 
clarity are reduced by freshwater runoff, and from unprotected 
areas. Until a size of typically 30 cm is reached, the species is 
weakly byssally attached to coral pieces or rubble.

Population Status and Abundance Trends
    The petition does not provide estimates of population abundance or 
trends for T. derasa; however, the petition does provide some 
information on population status or trends from individual locations 
within the species' range. A small population of T. derasa (initial 
baseline survey counted 44 individuals) showed an annual mortality of 
4.4 percent at Michaelmas Cay on the Great Barrier Reef between 1978 
and 1985 (Pearson and Munro 1991). Rubec et al. (2001) notes that T. 
derasa, among other species, was depleted and no longer commercially 
harvestable in the Philippines, although the authors do not provide an 
original source of that information. Teitelbaum and Friedman (2008) 
refer to the extirpation of T. derasa in Vanuatu but do not provide a 
reference for that information. The authors also report that Vanuatu 
has a restocking program that includes T. derasa. Teitelbaum and 
Friedman (2008) report that the reintroduction of approximately 25,000 
T. derasa to Yap from neighboring Palau in 1984 resulted in only 
approximately 8 percent survival of the introduced

[[Page 28961]]

stock. However, these T. derasa matured, reproduced, and re-established 
viable populations on nearby reefs (Lindsay 1995). Surveys conducted by 
the Secretariat of the Pacific Community (PROC-Fish/C-CoFish 
programmes) noted the continued presence of T. derasa in Yap in low 
numbers in mid-2006.
    The petitioner cites Tan and Yasin (2003), stating giant clams of 
all species but T. crocea are considered endangered in Malaysia. The 
authors mention underwater surveys that reveal ``distribution of giant 
clams are widespread but their numbers are very low,'' but the authors 
did not provide any references with any more detail or support for this 
information, which makes it difficult to interpret this information for 
individual species. Brown and Muskanofola (1985) found only one 
individual of T. derasa during a survey carried out in Karimun Jawa, a 
group of islands off the north coast of Central Java, Indonesia, 
surmising the species was essentially functionally extinct in this 
area. At another site in Indonesia, the petition cites Hernawan (2010), 
stating that they found small populations and evidence of recruitment 
failure in the six species found during a survey of Kei Kecil, 
Southeast-Maluku, including T. derasa. The authors conducted giant clam 
surveys in nine sites in this area. However, Indonesia encompasses 
thousands of islands and T. derasa occurs in other locations throughout 
Indonesia (Hernawan 2010). Therefore, these two studies represent a 
small sample of T. derasa abundance in Indonesian waters.
    Hardy and Hardy (1969) did a seminal study of ecology of Tridacna 
in Palau in the 1960s where T. derasa and T. gigas made up the largest 
proportion of the standing crop biomass because of their size. Hester 
and Jones (1974) recorded densities of 50 T. gigas and 33 T. derasa per 
hectare at Helen Reef, Palau; the petition notes that this study was 
conducted before these stocks were ``totally decimated by distant-water 
fishing vessels,'' but provides no information or references to 
document this ``decimation.''
    While individually and collectively, the studies discussed in this 
section represent a small portion of T. derasa's total geographic 
range, the small population sizes and extirpations of this species in 
small areas are spread throughout its range and are not confined to one 
or few areas that may be disproportionately affected by some negative 
impact. Therefore, the number and spatial distribution of small 
populations or local extirpations in the context of the species' range 
may be contributing to an elevated extinction risk for this species 
such that it warrants further investigation.
Threats to T. derasa
    Beyond the generalized threats to all giant clam species discussed 
above, the petition presents little information on threats to T. derasa 
specifically. According to Munro (1992), historical commercial 
fisheries appear to have been confined to long-range Taiwanese fishing 
vessels, which targeted the adductor muscles of the larger species 
(e.g., T. gigas and T. derasa). There are anecdotal claims in several 
of the references discussed above that harvest led to low population 
levels at certain study sites (e.g. Rubec et al., 2001, Teitelbaum and 
Friedman 2008, Tan and Yasin 2003, Brown and Muskanofola 1985, and 
Hernawan 2010), but none of those studies provide empirical evidence of 
declining trends or of potential causes of low population numbers. The 
petition cites Lewis et al. (1988), stating that the Fijian fishery for 
T. derasa landed over 218 tons over a 9-year period, with the largest 
annual harvest totaling 49.5 tons and which is ``thought to have 
removed most of the available stock.'' We find this to be a slight 
mischaracterization of what Lewis et al. (1988) state about T. derasa 
in Fiji based on 26 surveys between 1984-1987:

    Tridacna derasa: Widespread throughout the group, but generally 
rare on the fringing reefs of the main islands where terrestrial 
influence is strong, and in the leeward islands (yasawas) where 
sheltered oceanic lagoons are generally wanting. In 1984-85, there 
were still abundant populations on various reefs in the windward 
(Lau, Lomaiviti) islands, but subsequent commercial harvest has 
considerably reduced these numbers. Isolated pockets still remain 
and should be protected. Densities on inhabited windward islands 
generally low, with remaining individuals in deeper water (10 m 
plus). Further commercial harvests for export should be prohibited.

    According to CITES documents, commercial harvest for export is now 
prohibited in Fiji and the fisheries department cultures clams, 
including T. derasa, for restocking programs. Wild populations have 
been improving; currently reseeding occurs mostly in marine protected 
areas with 200 sites reseeded annually (CITES 2009). However, 
challenges remain for poaching at night.
    A 2004 CITES trade review for T. derasa indicates that out of 11 
countries where T. derasa is traded, one was assessed as ``Urgent 
Concern'' (Tonga), two as ``Possible Concern,'' and the remaining eight 
as ``Least Concern.'' The review also notes that international trade in 
T. derasa was reported from an additional 14 countries not selected for 
review and that for most countries no population monitoring seems to be 
in place and harvest and use of giant clams are inadequately regulated 
or not at all.
    The petition cites Bliderg (2000), who studied the effect of 
increasing water temperature by 3 [deg]C on cultured T. derasa, and 
several other species, for 24 hours. Results showed reduced gross 
production and decreased respiration of oxygen in response to the 
temperature increase however, different species of clams demonstrated 
different results, indicating different strategies for dealing with 
heat stress. None of the treated specimens exhibited any bleaching 
during the experiment. We acknowledge these results, but note they are 
not easily interpreted to determine potential individual or species 
level effects over time and/or space for T. derasa. The clams used in 
the experiment were cultured and not harvested from the wild. Cultured 
specimens are likely to experience much more uniform environments and 
are likely not acclimated to the common daily fluctuations in many 
environmental parameters experienced in the wild. As such, their 
responses to abrupt changes in their environment may differ from those 
of wild specimens. Given the heterogeneity of the species' habitat and 
current environmental conditions across its range, these results are 
not compelling evidence of a threat related to increased water 
temperature that is acting or will act on T. derasa to the extent that 
the petitioned action may be warranted.
Conclusion
    In conclusion, the information provided on threats for this species 
is limited and by itself would not be considered substantial 
information indicating the petitioned action may be warranted. The 
individual studies presented are not compelling evidence of species 
level concerns for reasons discussed above, however, taken together 
they provide sufficient evidence such that further investigation is 
warranted. The evidence presented of small, localized populations or 
extirpations in different parts of the species range is compelling 
enough to conclude that the petitioned action may be warranted. The 
best available information on all potential threats to the species will 
be evaluated in a forthcoming status review to determine what has 
potentially caused the observed declines and extirpations, and the 
extent to which such declines have occurred.

[[Page 28962]]

Tridacna gigas

Species Description
    Tridacna gigas is the largest of all the giant clam species, 
growing to a maximum shell length of 137 cm, with weights in excess of 
200 kg. However, the species is most commonly found at lengths up to 80 
cm (Neo et al., 2015; Kinch and Teitelbam 2009). The shell exterior is 
off-white and is often strongly encrusted with marine growths. The 
shell interior is porcellaneous white, and the mantle is yellowish 
brown to olive green, with numerous, small, brilliant blue-green rings, 
particularly along the lateral edges (Kinch and Teitelbaum 2009). This 
species may be readily identified by its size and by the elongate, 
triangular projections of the upper margins of the shells (Lucas 1988).
Life History
    In addition to the Life History section above on giant clams in 
general, the petition provided some species-specific life history 
information for T. gigas. The petition cited Braley (1988), who found 
that the optimal reproductive season for T. gigas sampled from 
Michaelmas Cay and Myrmidon Reef in Australia was October to February. 
Munro (1992) noted that spawning of T. gigas is restricted to a short 
summer season in the central region of the Great Barrier Reef. For T. 
gigas, von Bertalanffy growth parameter estimates include an asymptotic 
length (L[infin]) of 80 cm, growth coefficient (K) of 0.105, and a 
theoretical date of `birth' (t0) of 0.145 (Neo et al., 2015). According 
to Branstetter (1990), growth coefficients (K) falling in the range of 
0.05-0.10/yr are for slow-growing species; 0.1-0.2 for a moderate-
growing species; and 0.2-0.5 for a fast-growing species. Under these 
parameters, the giant clam T. gigas is considered a moderate-growing 
species. However, the petition notes that there are major differences 
between typical non-symbiotic bivalves and T. gigas regarding the 
relative allocations of energy to respiration and growth. For example, 
Klumpp et al. (1992) showed that T. gigas is an efficient filter-feeder 
and that carbon derived from filter-feeding in Great Barrier Reef 
waters supplies substantial proportions of the total carbon needed for 
respiration and growth.
Range, Habitat, and Distribution
    Prior to the rapid escalation of the aquarium trade, T. gigas could 
be found throughout the shallow tropical waters of the Indian and 
Pacific oceans; however, the recent fossil record, together with 
historical accounts show that the range of T. gigas has been 
dramatically reduced (see the Population Status and Abundance Trends 
section below; Munro 1992; bin Othman et al., 2010). The species' range 
once extended from East Africa to Micronesia and Australia to Japan. 
Like other giant clam species, T. gigas is typically associated with 
coral reefs and can be found in many habitats, whether high- or low-
islands, lagoons or fringing reefs (Munro 1992).
[GRAPHIC] [TIFF OMITTED] TP26JN17.004

Population Status and Abundance Trends
    The petition does not provide overall estimates of population 
abundance or trends for T. gigas. The petition does provide several 
lines of evidence that T. gigas has experienced a number of local 
extirpations in various locations throughout its range. Munro (1992) 
reports that while relict stocks of T. gigas occur in Indonesian, 
Malaysian, and Philippines waters and possibly on the west coast of 
Thailand and in southern Burma, in most cases it appears that these 
stocks are functionally extinct because of the wide dispersal of the 
survivors, making successful fertilization unlikely. In a more recent 
survey from Indonesian waters, T. gigas was surprisingly found in 
Ohoimas, where it was previously believed to be extinct (Hernawan 
2010). However, only four individuals were found in only one of nine 
sites surveyed. Additionally, several sources (Munro 1992; Teitelbaum 
and Friedman 2008; Kinch and Teitelbaum 2009) note

[[Page 28963]]

local extirpations of T. gigas have occurred in the Commonwealth of the 
Northern Mariana Islands, Federated States of Micronesia (Yap, Chuuk, 
Pohnpei, and Kosrae), Fiji, Guam, New Caledonia, Taiwan, Ryuku Islands 
(Japan), and Vanuatu. Neo and Todd (2012a, 2013) report that T. gigas 
is also nationally extinct in Singapore. In Australia, the T. gigas 
population from the Great Barrier Reef is essentially a relict 
population, consisting primarily of large adult clams; the lack of 
younger, faster-growing T. gigas clams is likely the reason for the 
species' low annual production of new biomass (Neo et al., 2015). 
Further, Kinch and Teitelbaum (2009) also report declining stocks of T. 
gigas across the three main island groups in Kiribati.
    Thus, while quantitative abundance estimates are unavailable for T. 
gigas throughout its range, the numerous local extirpations of T. gigas 
documented across a large portion of its range may be contributing to 
an elevated extinction risk for this species such that it warrants 
further investigation.
Threats to T. gigas
    As noted previously, giant clams in general are considered a 
valuable fishery target in many countries, with uses for both local 
consumption and commercial trade. Based on information in the petition 
and our files, it is clear that T. gigas is the most heavily exploited 
species of all giant clams, which has likely led to its substantial 
declines and extirpations in a number of locations throughout its 
range. As discussed previously in the general threats section for giant 
clams, the petition emphasizes the threat of the growing giant clam 
industry in China, largely the result of improved carving techniques, 
tourism in Hainan, China, the growth in e-commerce, and the domestic 
Chinese wholesale market (Larson 2016). The petition also raises 
concerns that stricter enforcement of the trade in ivory products has 
diverted attention to giant clam shells (McManus 2016). The petition 
points out that the giant clam (T. gigas) is preferentially targeted 
for international trade due to its large size and because it is 
considered a desirable luxury item in China thought to confer 
supernatural powers and improve health. As noted previously, a pair of 
high quality shells (from one individual) can fetch up to US $150,000. 
Therefore, the high value and demand for large T. gigas shells may be a 
driving factor contributing to overutilization of the species.
Conclusion
    Overall, we conclude that the information presented in the petition 
and our files provides substantial evidence that the petitioned action 
for T. gigas may be warranted. This species has likely experienced 
significant population declines and local extirpations in several 
locations throughout its range, likely due to historical and ongoing 
overutilization for commercial purposes and further investigation is 
warranted. The best available information on its overall status and all 
potential threats to the species will be evaluated in a forthcoming 
status review.

Tridacna squamosa

Species Description
    Although the petition notes that T. squamosa, also known as the 
fluted clam, grows to 19 cm based on Neo et al. (2015), we find this 
information is in error. Neo et al. (2015) report shell lengths of up 
to 40 cm for the species, and information in our files suggests it is 
most commonly found at lengths up to 30 cm (Kinch and Teitelbaum 2009). 
The shell exterior is described as ``greyish white, often with 
different hues of orange, yellow, or pink to mauve, and with the blade-
like scales commonly of different shades or color'' (Kinch and 
Teitelbaum 2009). The shell interior is porcelaneous white, 
occasionally tinged with orange, and the mantle is mottled in various 
mixes of green, blue, brown, orange, and yellow (Kinch and Teitelbaum 
2009).
Life History
    Aside from the general giant clam life history information already 
discussed previously in the Giant Clam Life History section, the 
petition provided little information specific to T. squamosa. Tridacna 
squamosa is a mixotroph whose photoautotrophic range is extended by 
heterotrophy. We found that T. squamosa reaches sexual maturity at 
sizes of 6 to 16 cm, which equates to a first year of maturity at 
approximately 4 years old (CITES 2004a).
Range, Habitat, and Distribution
    Tridacna squamosa has a widespread distribution across the Indo-
Pacific, but is slightly more restricted than T. maxima (Munro 1992). 
Its range extends from the Red Sea and East African coast across the 
Indo-Pacific to the Pitcairn Islands. It has also been introduced in 
Hawaii (CITES 2004a). The species' range also extends north to southern 
Japan, and south to Australia and the Great Barrier Reef (bin Othman et 
al., 2010). This range description reflects the recent range extension 
of T. squamosa to French Polynesia as a result of observations by 
Gilbert et al. (2007). The petition notes that T. squamosa occurred in 
Singapore and the United States historically; however, there is no 
supporting reference or evidence provided of the species' occurrence in 
the United States or its territories.

[[Page 28964]]

[GRAPHIC] [TIFF OMITTED] TP26JN17.005

    Tridacna squamosa is usually found near reefs or on sand; it is 
found attached by its byssus to the surface of coral reefs, usually in 
moderately protected areas such as reef moats in littoral and shallow 
water to a depth of 20 m (Kinch and Teitelbaum 2009). This species 
tends to prefer fairly sheltered lagoon environments next to high 
islands; however, T. squamosa appears to be excluded by T. maxima in 
the closed atoll lagoons of Polynesia (Munro 1992). Neo et al. (2009) 
found that T. squamosa larvae, like many reef invertebrates, prefer 
substrate with crustose coralline algae. Tridacna squamosa is also 
commonly found amongst branching corals (staghorn, Acropora spp.; CITES 
2004a)
Population Status and Abundance Trends
    The petition provides limited some information regarding the 
species' population status and trends from Singapore, Samoa, and 
individual sites in Malaysia, Philippines, Indonesia, and Thailand.
    The petitioner states that T. squamosa is functionally extinct in 
Samoa based on a study from western Samoa (Zann and Mulipola 1995). 
This study relied on a range of low technology methods developed for 
rapid environmental and fisheries assessments. Fisheries surveys were 
conducted via interviews and surveys of fishermen and households, and 
results were compared with commercial market landings from the Apia 
municipal fish market on the island of Upolu. From 1985 to1990, annual 
landings of all giant clams dropped from 10 metric tons to 0.1 metric 
tons and field surveys indicated that T. squamosa was so rare it was 
functionally extinct. The authors note that fishing effort also 
declined around 35 percent between 1983 and 1991, which is considered 
to be partially responsible for the declines in landings, although 
other factors likely contributed (e.g., overfishing of inshore stocks, 
use of destructive fishing techniques, etc.). Information in our files 
suggests that this species has been the subject of restocking efforts 
in Samoa. Since 1988, T. squamosa has been trans-located from Palau, 
Tokelau, and Fiji to restock populations in Samoa under the Samoan 
Community-based Fisheries Management program (Kinch and Teitelbaum 
2009).
    In Singapore, Neo and Todd (2012a) surveyed 29 reefs, covering an 
estimated 87,515 m\2\ and observed 28 T. squamosa individuals, which 
was double the number observed in a 2003 survey of only 7 reefs and a 
little over 9,000 m\2\ by Guest et al. (2008). However, Neo and Todd 
(2012a) estimate T. squamosa density to be 0.032 per 100 m\2\, which is 
five times lower than the 0.16 per 100 m\2\ measured in 2003 (Guest et 
al., 2008). They go on to propose that habitat loss, exploitation, and 
or sediment have synergistically led to the endangered status of T. 
squamosa in Singapore's waters. Neo and Todd (2013) make a similar 
conclusion, stating that ``the low density and scattered distribution 
of the remaining T. squamosa in Singapore are likely to significantly 
inhibit any natural recovery of local stocks.'' However, the authors 
specifically make the point that the status of a species at a small 
scale (individual country or an island as may be the case for 
Singapore) is most often not representative of its global status. Any 
species, especially one with a large range like T. squamosa, will have 
variable statuses at smaller scales in different habitats due to a 
variety of factors. Singapore is a small and densely populated island 
nation known for particularly high anthropogenic impacts in its 
nearshore waters. The information in Neo and Todd (2012a 2012b and 
2013) is informative for resource managers in Singapore and indicates a 
very low population and density of T. squamosa. However, it is unclear 
how the current information relates to historical abundance of this 
species at this location. In addition, it is not necessarily useful for 
assessing the global status of T. squamosa because Singapore is a very 
small proportion of the overall species' range and is not a 
representative environment of the rest of the species' range.
    The petitioner cites Tan and Yasin (2003), stating that giant clams 
of all species but T. crocea are considered

[[Page 28965]]

endangered in Malaysia. As discussed previously, the authors of this 
study mention underwater surveys that reveal that the ``distribution of 
giant clams are widespread but their numbers are very low.'' However, 
there are no references provided by the authors to provide any more 
detail or support for this information, which makes it difficult to 
interpret this information for individual species. The only species-
specific information for T. squamosa in this reference is that it 
occurs in Malaysian waters.
    The petitioner cites Thamrongnavasawat et al. (2001) as saying T. 
squamosa are now considered ``scarce'' throughout Thailand. However, 
the link provided in the bibliography to access this reference was not 
functional, and we were otherwise unable to obtain and review this 
reference to determine what the authors meant by ``scarce'' or on what 
evidence this statement was based. However, the petitioner provides 
other studies from Thailand indicating that the species has likely 
undergone significant declines in this area. For example, 
Chantrapornsyl et al. (1996) documented heavy exploitation and local 
extirpation of T. squamosa in the Andaman Sea. Kittiwattanawong (1997) 
also concluded that T. squamosa was rare in the same area. Tridacna 
squamosa was also deemed ``near extinct'' in Mo Ko Surin National Park 
in Thailand (Dolorsa and Schoppe 2005).
    Villanoy et al. (1988) examined average size frequency 
distributions of T. squamosa harvested from the Sulu Archipelago and 
Southern Palawan areas in the Philippines from 1978 to 1985, and 
determined that estimates of exploitation rates indicate that 
populations of these species are overexploited. The petitioner asserts 
that these findings have serious implications given that the Sulu 
Archipelago and Southern Palawan are thought to be the last strongholds 
of giant clams species occurring in Philippine waters. Dolorosa and 
Schoppe (2005) also report that T. squamosa had very low densities in 
surveys conducted in Tubbataha Reef National Marine Park in the 
Philippines. The authors note that because of the species' low 
settlement, survival and growth on live coral substrate, it would take 
hundreds of years for the stock to be re-established, particularly in 
isolated areas. However, the authors also note that the numbers seen at 
Tubbataha Marine Park are significantly lower than in other areas of 
the Philippines; therefore, the situation in the marine park may not be 
representative of the species' status across the Philippines as a whole 
(Dolorosa and Schoppe 2005). The petitioner also cited a stock 
assessment conducted in Eastern Visayas, in the Philippines (Salazar et 
al., 1999), which showed that while T. squamosa are common in the Samar 
Sea and San Pedro Bay, most of the giant clams surveyed were in the 
juvenile stage with no breeders left to repopulate the area. However, 
the Marine Science Institute (MSI) at the University of the Philippines 
has a long and successful record of rearing, having cultured giant 
clams to restore depleted supplies for the last 20 years. In fact, more 
than 40 sites have received cultured clams and MSI promotes giant clam 
farming as a sustainable livelihood with restocking activities 
occurring in collaboration with local groups (bin Othman et al., 2010).
    As discussed previously, the petition also broadly states that all 
six giant clam species occurring in Indonesia, including T. squamosa, 
are experiencing recruitment failure based on a single study from Kei 
Kecil, Southeast-Maluku, Indonesia (Hernawan 2010). Hernawan (2010) 
conducted giant clam surveys in 9 sites; however, Indonesia encompasses 
thousands of islands and T. squamosa occurs in several other locations 
throughout Indonesia (Hernawan 2010). Thus, this study represents a 
very small sample of T. squamosa abundance in Indonesian waters, with 
no evidence provided to suggest that recruitment failure of T. squamosa 
is occurring throughout Indonesia.
    Overall, given the extensive range of T. squamosa, the information 
provided in the petition is limited regarding the population status and 
abundance trends of the species throughout its range. While we 
acknowledge that in some locations (primarily Southeast Asia), 
abundance and/or density of T. squamosa may be low, the petition did 
not provide any information regarding the species' status from a large 
majority of its range. For example, in addition to countries in 
Southeast Asia, T. squamosa can be found throughout Oceania (e.g., 
Australasia, Melanesia, Micronesia and Polynesia). The species also 
inhabits coastlines of the Indian Ocean and has a relatively 
cosmopolitan distribution in this region (bin Othman et al., 2010). 
Thus, no information was presented in the petition for an entire two 
thirds or more of the species' range (i.e., Oceania (with the exception 
of Samoa), eastern Africa, and the Indian Ocean). However, a lack of 
information on its own does not mean the action may not be warranted if 
the lack of information itself may be considered a risk to the species. 
In this case, given that the only information we have indicates 
historical declines, low population levels, and notably local 
extirpations in some locations, we conclude that the information 
presented in the petition regarding the species' abundance and 
population trends is compelling enough to warrant further investigation 
in a forthcoming status review.
Threats to T. squamosa
    Given that T. squamosa is a large, free-living species of giant 
clam, it is easier to remove from the reef (Neo and Todd 2013), which 
makes it more susceptible to harvest for local consumption and/or 
commercial purposes. Some information (albeit limited) provided by the 
petition suggests that T. squamosa may be overexploited in some 
locations. As discussed earlier in the Population Status and Abundance 
Trends section for T. squamosa, estimates of exploitation rates from 
the Sulu Archipelago and Southern Palawan areas of the Philippines from 
1978 to 1985 indicate that populations of T. squamosa were 
overexploited.
    Information in our files indicates that T. squamosa is important in 
the subsistence fishery of Papua New Guinea. A commercial fishery for 
giant clams previously operated in the Milne Bay Province, whereby 
approximately 150 tonnes of giant clam adductor muscle were exported, 
as well as one large shipment of 16 tonnes of giant clam shells. 
However, this fishery has been closed since 2000 and we could not find 
any additional information in our files regarding the utilization of T. 
squamosa in Papua New Guinea. We also found some information regarding 
the reported functional extinction of this species in Samoan waters, 
and acknowledge that the significantly low density of T. squamosa in 
Samoa is largely attributed to overfishing (Kinch and Teitelbaum 2009); 
however, as noted previously, to mitigate low populations, restocking 
efforts have been underway in Samoa since the 1980s, and from 1998 to 
2000, Samoa has seen the importation of several giant clam species, 
both larvae and `yearlings,' for restocking purposes under the Samoan 
Community-based Fisheries Management program (Kinch and Teitelbaum 
2009). Nevertheless, we cannot confirm whether this restocking program 
has been successful for T. squamosa.
    In terms of commercial trade, a significant trade review was 
conducted in 2004 for 27 countries that trade in T.

[[Page 28966]]

squamosa to identify potential areas of concern. Of the 27 countries 
reviewed, 24 were deemed to be of ``least concern'' for various 
reasons; the respective countries had either not reported any trade, or 
trade levels were minimal or export numbers were low. Two countries 
(Marshall Islands and Tonga) were deemed to be of ``possible concern'' 
and only one country (Vietnam) was categorized as ``urgent concern.'' 
These designations were made largely because trade of the species 
continues despite export bans or because, in the case of Vietnam, 
significant trade was occurring (e.g., 74,579 live T. squamosa clams 
were exported from 1994 to 2003) with a lack of information on 
population monitoring or the basis for non-detriment findings under 
CITES. Additionally, in the case of the Marshall Islands, where trade 
seems to continue despite export bans, the review also notes that 
several small-scale operations were producing farmed (i.e., captive-
bred) T. squamosa in the 1990s for the aquarium trade and for reseeding 
depleted areas, and that records of trade in wild rather than captive-
bred specimens may be a result of misreporting by importing parties 
(CITES 2004a). Based on the information presented in the petition and 
in our files summarized here, we cannot conclude that there is 
sufficient evidence to suggest that trade of T. squamosa is an 
operative threat that acts or has acted on the species to the point 
that the petitioned action may be warranted.
    Overall, the species-specific information in the petition and in 
our files to support the claim that T. squamosa is experiencing 
overutilization to the point that the petitioned action may be 
warranted is limited, particularly given the broad geographic range of 
the species. While there are anecdotal claims in several of the 
references that are discussed above that low population levels at 
certain study sites are due to harvest (i.e., Teitelbaum and Friedman 
2008, Tan and Yasin 2003, and Hernawan 2010), none of those studies 
provide empirical evidence of declining trends.
    In addition to overutilization, the petitioner also claims that T. 
squamosa is at risk of extinction due to climate change-related 
threats, including ocean warming and acidification. In Singapore, local 
bleaching of T. squamosa was observed during a high sea surface 
temperature event in June 2010 (Neo and Todd 2013); however, no other 
information was provided regarding the extent of bleaching that 
occurred nor whether the species experienced significant mortality as a 
result. In a lab experiment using cultured clams, short-term 
temperature increases of 3 [deg]C resulted in T. squamosa clams 
maintaining a high photosynthetic rate but displaying increased 
respiratory demands (Elfwing et al., 2001). Finally, Watson et al. 
(2012) showed that a combination of increased ocean CO2 and 
temperature are likely to reduce the survival of T. squamosa. 
Specifically, in a lab experiment, T. squamosa juvenile survival rates 
decreased by up to 80 percent with increasing pCO2 and 
decreased with increasing seawater temperature for a range of 
temperatures and pCO2 combinations that mimic those expected 
in the next 50 to 100 years.
    We acknowledge these results, but they are not easily interpreted 
into potential species level effects over time and/or space for T. 
squamosa. First, the clams used in the experiments were cultured and 
not harvested from the wild. Cultured specimens are likely to 
experience much more uniform environments and are likely not acclimated 
to the common daily fluctuations in many environmental parameters 
experienced in the wild. As such, they may react differently than wild 
specimens to abrupt changes in their environment. Additionally, 
information and references in our files acknowledge that there are 
limitations associated with applying results from laboratory studies to 
the complex natural environment where impacts will be experienced 
gradually over the next century at various magnitudes in a non-uniform 
spatial pattern. In general, lab experiments presented do not reflect 
the conditions the petitioned species will experience in nature; 
instead of experiencing changes in levels of ocean warming and 
acidification predicted for the end of the century within a single 
generation, species in nature are likely to experience gradual 
increases over many generations. However, we recognize that because 
giant clam species are likely long-lived, they likely have longer 
generation times, and thus, giant clams born today could potentially 
live long enough to experience oceanic conditions predicted late this 
century (Watson et al., 2012). Overall, the information regarding 
negative species-specific impacts from climate change to T. squamosa is 
limited; however, we will thoroughly review climate change related 
threats and their potential impacts to T. squamosa in a forthcoming 
status review.
Conclusion
    In conclusion, the information provided on threats for this species 
is limited and by itself would not be considered substantial 
information indicating the petitioned action may be warranted. However, 
combined with the evidence presented of small, localized populations or 
extirpations in different parts of the species' range, we conclude the 
information presented in the petition is compelling enough to conclude 
that the petitioned action may be warranted. Therefore, we conclude 
that the number and spatial distribution of localized severe declines 
or extirpations in the context of the species' range may be 
contributing to an elevated extinction risk for this species such that 
it warrants further investigation. Thus, the best available information 
on overall status and potential threats to the species will be 
evaluated in a forthcoming status review to determine what has 
potentially caused these declines and extirpations and the overall 
extinction risk for the species.

Tridacna tevoroa

Species description
    Tridacna tevoroa is another recently described species that has 
been shown to actually be a junior synonym of a previously described 
species, T. mbalavauna (Borsa et al., 2015a). The petition notes that 
T. tevoroa looks most like T. derasa in appearance, but can be 
distinguished by its rugose mantle, prominent guard tentacles present 
on the incurrent siphon, thinner valves, and colored patches on shell 
ribbing (Neo et al., 2015). T. tevoroa has an off-white shell exterior, 
often partially encrusted with marine growths. The shell interior is 
porcellaneous white, with a yellowish brown mantle (Kinch and 
Teitelbaum 2009). It can grow to just over 50 cm long (Neo et al., 
2015).
Life History
    Aside from what has already been discussed in terms of life history 
information for giant clams in general (refer back to the Giant Clam 
Life History section above), the petition did not describe any species-
specific life history information for T. tevoroa. However, in one of 
the references cited by the petitioner we found some additional 
information related to spawning of T. tevoroa clams. During a study of 
spawning and larval culture of T. tevoroa (Ledua et al., 1993), 
successful spawning of T. tevoroa at the Tonga Fisheries Department in 
late October 1991 indicates that this species has a breeding season 
that may be

[[Page 28967]]

similar to that of T. derasa. Ledua et al. (1993) describe that the 
breeding season of T. derasa on the Great Barrier Reef in Australia is 
from late winter-early spring to early summer and virtually all 
individuals are spent by mid-December. In Fiji, the breeding program 
for this species is from July to October and in Tonga from September to 
late November (Ledua et al., 1993). It must be noted that the examples 
of the breeding season of T. derasa given here are from higher 
latitudes within the tropics (17[deg]-21[deg]S), while there is 
evidence from hatchery spawnings at lower latitudes (Palau, 7[deg]N) 
that T. derasa has an almost full year breeding season (Heslinga et 
al., 1984 cited in Ledua et al., 1993).
Range, Habitat, and Distribution
    Tridacna tevoroa appears to have a restricted distribution. 
Although the petition says that T. tevoroa is restricted to Tonga and 
Fiji, information in our files indicates that this species was recently 
observed in the Loyalty Islands of New Caledonia as well (Kinch and 
Tietelbam 2009). Tridacna tevoroa can typically be found on sand in 
coral reef areas. In Fiji, T. tevoroa live along outer slopes of 
leeward reefs, in very clear, oceanic water at 9-33 m depth (Ledua et 
al., 1993). Based on the distribution of adults in Fiji and Tonga, it 
appears that juveniles settle on slopes of off-shore reefs in deep 
(down to 33 m) oceanic waters. However, juvenile T. tevoroa have never 
been found in nature (Klump and Lucas 1994).
[GRAPHIC] [TIFF OMITTED] TP26JN17.006

    Tridacna tevoroa has a unique depth distribution among the giant 
clam species; it is the only species to occur in depths below 20 m. In 
order to better understand how T. tevoroa survives in deeper waters, 
Klumpp and Lucas (1994) compared nutrition of T. tevoroa with T. derasa 
in Tonga, where rates of filter-feeding, respiration and the 
photosynthesis-irradiance response were measured in clams of a wide 
size range (ca 20 mm to ca 500 mm). Only T. tevoroa significantly 
increased its photosynthetic efficiency with increasing depth. In a 
study on spawning and larval culture of T. tevoroa clams, individuals 
were collected from waters of Fiji and Tonga (Ledua et al., 1993). The 
mean depth of clams collected in Fiji was 27.4 m, with samples 
collected from depths ranging from 20 to 33 m. All specimens were found 
on the leeward side of reefs and islands. Ledua et al., (1993) notes 
that: ``Many of the clams found in Tonga were adjacent to the edge of a 
sand patch and cradled against rocky outcrops, rubble or bare rock with 
steep slopes.'' During the SCUBA search in February 1992 in Ha'apai 
(Tonga), two of the authors notably found a considerable number of T. 
tevoroa on live coral (whereas in Fiji, these clams have not been found 
on live coral, possibly because little live coral was found at this 
depth in the Lau Islands group). About half of the clams in Tonga were 
found on the leeward and half on the windward side of reefs. However, 
windward sides of reefs were still somewhat protected within barrier 
islands or reefs, and no search has yet been made on outer windward 
reefs (Ledua et al., 1993). Overall, spatial distribution of T. tevoroa 
appears to be very sparse, with single individuals being found at most 
locations, although clumps of four individuals were seen twice and 
other smaller clumps were seen in Tonga, which could represent small 
breeding groups for this species (Ledua et al., 1993). Given the large 
areas of suitable reefs and shoals with typical habitat for T. tevoroa, 
Ha'apai, Tonga may be the center of distribution and largest repository 
of this newly-described species (Ledua et al., 1993).
Population Status and Abundance Trends
    The petition provides only one reference for T. tevoroa with regard 
to its population status or abundance trends. Ledua et al. (1993) 
describes T. tevoroa as a rare species and notes that few specimens 
have been found live in Fiji, and only recently larger numbers of this 
species have been found in Tongan waters. Anecdotal reports from one 
diver from Uiha Island, Ha'apai, Tonga note that the species was 
historically more abundant in shallow waters during

[[Page 28968]]

the 1940s (Ledua et al., 1993). Based on this limited information, the 
petitioner speculates that T. tevoroa has declined significantly in 
accessible waters and states that the species' current abundance is 
likely lower than historical levels. However, the petitioner did not 
provide any additional references or supporting information to 
substantiate the claim regarding the species' current population 
status. The petitioner also provided no additional information 
regarding the species' population status or abundance trends from other 
portions of its range (i.e., Fiji or New Caledonia). Nonetheless, given 
that the species is described as rare, has one of the most restricted 
ranges of the giant clam species, and has likely undergone some level 
of population decline in its potential center of distribution (i.e., 
Tonga), we find this information may indicate an elevated extinction 
risk for this species, and is compelling enough to warrant further 
investigation.
Threats to Tridacna tevoroa
    Very little species-specific information on threats is presented in 
the petition for T. tevoroa. Aside from what has already been discussed 
regarding the threat of overutilization of giant clams in general 
(refer back to the Threats to Giant Clams section above), the petition 
provides very limited species-specific information regarding 
overutilization of T. tevoroa for commercial, recreational, scientific, 
or educational purposes. As noted previously in the Abundance and 
Population Trends section, anecdotal reports from one diver from Uiha 
Island, Ha'apai, Tonga note that the species was historically more 
abundant in shallow waters during the 1940s. Evidence of former greater 
abundance and distribution in shallow water in Ha'apai may indicate 
that fishing pressure has likely contributed to the rarity of this 
species (Ledua et al., 1993). This is extremely limited information to 
suggest that overutilization is a threat to the species, particularly 
given the lack of information from Fiji and New Caledonia; however, 
given that Ha'apai Tonga is likely the center of distribution and 
largest repository for this particular species, we find that this 
information, combined with the species' rarity throughout its range, 
may be contributing to an elevated risk of extinction for this species.
Conclusion
    In conclusion, the information provided on threats for this species 
is limited and by itself would not be considered substantial 
information indicating the petitioned action may be warranted. 
Anecdotal evidence from one location of a species' range would 
generally not be compelling evidence of species level concerns 
throughout its range for reasons discussed above. However, the combined 
evidence on the species' restricted range, sparse distribution and 
rarity, and anecdotal evidence of population decline in the center of 
the species' distribution, is compelling enough to conclude that the 
petitioned action may be warranted. The best available information on 
its overall status and all potential threats to the species will be 
evaluated in a forthcoming status review.
Tridacna crocea
Species description
    Tridacna crocea is the smallest species of giant clam, reaching 
only 15 cm (Neo et al., 2015; Copland and Lucas 1988). The species is 
similar to T. maxima but smaller, less asymmetrical and with its scutes 
worn away except near the upper edge of the shell (Copland and Lucas 
1988). The shell exterior is: ``greyish white, often covered with 
yellow or pinkish orange and frequently encrusted with marine growths 
near the dorsal margins of valves, but clean and nearly smooth 
ventrally'' (Kinch and Teitelbaum 2009). The shell interior is 
porcellaneous white, sometimes with yellow to orange hues on margins. 
The mantle is often brightly colored and variable in both pattern and 
color, including shades of green, blue, purple, brown, and orange 
(Kinch and Teitelbaum 2009).
Life History
    The petition provided some species-specific information regarding 
T. crocea's life history. The petition noted that spawning of T. crocea 
in the central region of the Great Barrier Reef is thought to be 
restricted to a short summer season (Munro 1992), and T. crocea has 
been observed spawning during July in Palau (Hardy and Hardy 1969). In 
a detailed study of early life history in Guam, fertilized eggs of T. 
crocea had a mean diameter of 93.1[mu]m (Jameson 1976). This same study 
noted that settlement of T. crocea larvae occurred approximately 12 
days after fertilization.
    We found a limited amount of additional information in our files on 
the life history of this species. Tridacna crocea has the smallest size 
for adult giant clams and reaches full sexual maturity 
(hermaphroditism) at approximately 5 to 6 years of age. With reports 
that T. crocea individuals of approximately 8 to 9 cm shell length 
produce 3 to 4 million eggs (Tisdell 1994), this species has extremely 
high fecundity. As such, even with relatively high mortality rates, 
tridacnid populations like T. crocea can be rapidly increased by 
artificial breeding and culture programs (Tisdell 1994).
Range, Habitat, and Distribution
    Tridacna crocea has a large range, with distribution ranging from 
southern Japan to Australia, but not extending eastward into Oceana 
beyond Palau and the Solomon Islands (Munro 1992). The petition 
provides information on this species from Singapore, Malaysia, 
Philippines, Indonesia, Thailand, and Palau. We also found additional 
information in our files for T. crocea from Australia, Solomon Islands, 
Vanuatu, New Caledonia, Papua New Guinea, and Tonga.

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[GRAPHIC] [TIFF OMITTED] TP26JN17.007

    Tridacna crocea is unusual among other giant clam species in that 
it burrows deeply in coral masses of reef flats and coral heads (with 
the free valve margins nearly flush with the substrate surface) in 
shallow water to a depth of about 20 m (when the water is clear; 
Copland and Lucas 1988; Kinch and Teitelbaum 2009; Neo et al., 2015). 
According to Hamner and Jones (1974), T. crocea burrows as it grows, 
eroding the surfaces of coral boulders and producing structures that 
superficially resemble micro-atolls. In a study conducted in Indonesia, 
T. crocea individuals were mostly embedded in dead coral boulders 
covered by algae (82 percent), with a few living in Porites spp., coral 
rubble, and live coral substrate (only 1 percent; Hernawan 2010). This 
species remains attached to the substrate throughout its life (Copland 
and Lucas 1988). The species also appears to aggregate, though the 
mechanism is unclear. Aggregation (i.e., clumping) may enhance physical 
stabilization, facilitate reproduction, or provide protection from 
predators (Soo and Todd 2014).
Population Status and Abundance Trends
    The petition does not provide overall estimates of population 
abundance or trends for T. crocea. The petition does provide limited 
pieces of information regarding the species' population status and 
trends from Singapore, Malaysia, Philippines, Indonesia, Thailand, and 
Palau. The petitioner cites Neo and Todd (2012; 2013) to assert that T. 
crocea is likely functionally extinct in Singapore, as the species is 
reproductively isolated and unlikely to fertilize conspecifics. In the 
most recent status reassessment of giant clams, Neo et al. (2013) note 
that T. crocea surveys in Singapore from 2009/2010 put their density at 
a low 0.035 per 100 m\2\, but emphasize that abundance estimates for 
this species may be conservative as its burrowing behavior and cryptic 
coloration can lead to underestimates of abundance. Nonetheless, the 
species' population is considered to be small in Singapore, resulting 
in an endangered status locally. However, the authors specifically make 
the point that the status of a species at a small scale (individual 
country or an island as may be the case for Singapore) is not 
necessarily representative of its global status. Any species, 
especially one with a large range like T. crocea, will have variable 
statuses at smaller scales in different habitats due to a variety of 
factors. Singapore is a small and densely populated island nation known 
for particularly high anthropogenic impacts in its nearshore waters. 
The information in Neo and Todd (2012a 2012b and 2013) is informative 
for resource managers in Singapore and indicates a very low population 
and density of T. crocea. However, it is unclear how the current 
information relates to historical abundance of this species at this 
location. In addition, it is not necessarily useful for assessing the 
global status of T. crocea because Singapore is a very small proportion 
of the overall species' range and is not a representative environment 
of the rest of the species' range.
    The petition also asserts that T. crocea has declined by 94 percent 
in the Tubbataha Reef Park in the Philippines since the early 1990s 
based on a decline from 2,200,000 clams/km2 in 1993 
(Calumpong and Cadiz 1993) to 133,330 clams/km\2\ in 2005 (Dolorosa and 
Schoppe 2005). It should be noted that these numbers were derived from 
transects taken within the ``intertidal area'' of the park. Dolorosa 
and Schoppe (2005) characterized T. crocea as the most abundant and 
dense giant clam species in the study area, with 133,330 individuals 
per km\2\ in the intertidal area, and averaging 30,480 individuals per 
km\2\ in the shallow area (5 m). Dolorosa and Schoppe (2005) also noted 
that the much lower density observed in their study (as compared to the 
previous study by Calumpong and Cadiz (1993)) in the intertidal area is 
not enough to conclude that there is a continuous decline of tridacnids 
(including T. crocea) because the data were only taken from a single 
transect. Thus, their study is not likely representative of the entire 
intertidal area, let alone the entire Tubbataha Reef Park. Therefore, 
the petition's inference of a 94 percent

[[Page 28970]]

decline in T. crocea abundance in Tubbataha Reef Park based on a single 
transect is not supported. Additionally, Rubec et al. (2001) 
characterizes T. crocea as one of the most abundant giant clam species 
across the Philippines.
    The petition also broadly states that all six giant clam species 
occurring in Indonesia, including T. crocea, are experiencing 
recruitment failure based on one study from Kei Kecil, Southeast-Maluku 
(Hernawan 2010). Hernawan (2010) conducted giant clam surveys in nine 
sites throughout Kei Kecil waters. Results showed T. crocea to be the 
dominant species with the highest population density in each of the 
nine study sites. Similar results have been documented in other areas 
of Indonesia, including the Andaman Sea, Upanoi and Banchungmanee, 
Adang Islands and Seribu Islands, Raja Ampat (Hernawan 2010) and Pari 
Island (Eliata et al., 2003). Additionally, Indonesia is comprised of 
thousands of islands; thus, the Hernawan (2010) study cited by the 
petitioner represents a very small sample of T. crocea abundance in 
Indonesian waters, with no evidence provided to suggest that 
recruitment failure of T. crocea is occurring throughout Indonesia. 
Hernawan (2010) also noted that due to T. crocea's small size and 
burrowing behavior, fishermen find this particular species more 
difficult and less desirable to harvest. Thus, this species is not the 
main target for Indonesian fishermen, leading to it having the highest 
relative population density throughout the study area (Hernawan 2010).
    Finally, the petition notes that T. crocea was the only giant clam 
with a stable population in Malaysia and not considered ``endangered'' 
by the early 2000s and that the species was still abundant in 
Thailand's Mo Ko Surin National Park in the late 1990s (Tan and Yasin 
2003; Thamrongnavasawat 2001). Additionally, Hardy and Hardy (1969) 
described T. crocea as the most frequent and abundant giant clam 
species in Palau in the 1960s. No additional information could be found 
in the petition or in our files pertaining to more recent trends for T. 
crocea in these locations to indicate low abundance or declining 
population trends.
    In our own files, we found that T. crocea is one of the most 
abundant species of giant clam in New Caledonia (Kinch and Teitelbaum 
2009). In Papua New Guinea, information on stock status is limited with 
the exception of Milne Bay, where T. crocea was also considered the 
most abundant species. T. crocea is also found in Vanuatu, where, 
although all stocks of giant clam are generally regarded as declining, 
improvements have been noted in specific localities (Kinch and 
Teitelbam 2009); however, we could find no additional information 
specific to T. crocea. In a 2004 CITES assessment of international 
trade of the species, T. crocea was described in general as ``still 
reasonably abundant'' (CITES 2004b).
    Overall, the information regarding T. crocea's population status 
and abundance trends throughout its range is extremely limited, with 
most characterizations of this species' abundance being qualitative. 
Nonetheless, it appears, based on the information presented in the 
petition and in our files, that T. crocea is often the dominant giant 
clam species wherever it occurs, has some of the highest population 
densities of any species, and is the only species of giant clam with a 
stable population in Malaysia. Although information suggests T. crocea 
likely experienced a localized abundance decline in Okinawa, Japan, 
which represents a very small portion of the species' range, we could 
not otherwise find any information to indicate that the species' 
overall abundance or density is so low or declining so significantly 
that the petitioned action is warranted. Thus, we find the petition 
insufficient in terms of presenting substantial information that T. 
crocea's population status or abundance trends indicate that the 
petitioned action may be warranted.
Threats to Tridacna crocea
Factor A: Present or Threatened Destruction Modification, or 
Curtailment of Range
    The petition asserts that all species of giant clam, including T. 
crocea, are at risk of extinction throughout their ranges due to the 
threat of habitat destruction, largely as a result of threats related 
to climate change and coral reef habitat degradation. However, the 
petition does not provide any species-specific information with regard 
to how habitat destruction is negatively impacting T. crocea 
populations. As described previously, T. crocea does not appear to have 
an obligate relationship to a pristine, live coral reef habitat. In 
fact, T. crocea has been observed in a number of habitat types, 
including dead coral rubble covered in algae. Thus, and as noted 
previously, while the information in the petition is otherwise largely 
accurate and suggests concern for the status of coral reef habitat 
generally, its broadness, generality, and speculative nature, and the 
lack of reasonable connections between the threats discussed and the 
status of T. crocea specifically, means that we cannot find that this 
information reasonably suggests that habitat destruction is an 
operative threat that acts or has acted on the species to the point 
that the petitioned action may be warranted.
Factor B: Overutilization for Commercial, Recreational, Scientific, or 
Educational Purposes
    The petition contends that T. crocea warrants listing as a result 
of overutilization for commercial purposes, but only notes three 
locations in which overfishing of T. crocea is reportedly occurring 
(Fiji, Japan, and Vietnam) based on bin Othman et al. (2010). In a 
market evaluation conducted in the mid-1990s in Japan, T. crocea was 
considered a preferred species for use as sashimi and sushi dishes in 
Okinawa; in contrast, giant clams were unknown as a food source in 
mainland Japan. From 1975 to 1995, giant clam catches in Okinawa, Japan 
declined from 578 tons to 28 tons, likely due to stock depletion (Okada 
1998). Given that T. crocea comprises approximately 90 percent of the 
giant clams landed in Okinawa, it is likely that the species 
experienced historical overfishing in this location. Although 
overfishing of T. crocea may have occurred historically in Okinawa 
waters, mass seed culture and production of T. crocea have been 
undertaken in Japan to ensure natural stock enhancement, with 44,000-
459,000 seeds of T. crocea distributed to the fishermen's cooperatives 
annually from 1987 to 1995 for release into Okinawa waters (Okada 
1998). Survival of clams ranged up to 56 percent 3 years after release 
(Teitelbaum and Friedman 2008). Without any data since 1995, it is 
difficult to determine whether this fishery is ongoing, the success 
rate of the local restocking efforts, or the current status of T. 
crocea stocks in Okinawa. Nonetheless, Okinawa, Japan represents a very 
small portion of the species' overall range and it appears Japan has 
implemented some regulations and conservation efforts to help safeguard 
giant clam populations from overfishing.
    Aside from Japan, no other information or data is provided in the 
petition from Fiji or Vietnam to support the broad statement that 
overfishing of T. crocea is occurring in those locations, although we 
did find some trade data to indicate that T. crocea is subject to 
commercial trade in these areas (CITES 2004b). From 1994 to 2003, 
exports of T. crocea were recorded for 24 countries and territories. 
However, only ten of the 24 countries were selected for a

[[Page 28971]]

significant CITES trade review, of which only two were categorized as 
``possible concern'' (Fiji and Vanuatu) and only one country (Vietnam) 
was categorized as ``urgent concern.'' The remaining countries were 
described as having no or minimal trade, and consequently designated as 
``least concern.'' Of the 16 countries not selected for review and 
recording exports, only the Solomon Islands appeared to be trading in 
significant quantities (CITES 2004b).
    In Fiji, T. crocea is not recorded as naturally occurring but it 
has been reported as ``introduced.'' Between 1997 and 2000, significant 
quantities of T. crocea imports (~15,000 live specimens) were reported 
from Fiji, of which two-thirds were reported as being of wild origin. 
Reported imports from captive bred sources have virtually ceased since 
2000, and those from wild sources have declined significantly. However, 
the CITES review regarding trade of T. crocea in Fiji concluded that: 
``Without information on the status of introduced stocks and harvest 
levels for domestic consumption, it is not possible to assess whether 
or not current export levels are detrimental to the species' survival 
in Fiji'' (CITES 2004b).
    In Vietnam between 1998 and 2003, gross live exports of wild-
sourced T. crocea peaked at 61,674 specimens in 2001 and otherwise 
ranged between 35,000 and 46,000. Since 2001, much lower levels, albeit 
still substantial (i.e., from 2,500 to 7,500 specimens annually) of 
live T. crocea reported as captive-bred have been exported. The 
``Urgent Concern'' designation was given to Vietnam because of the 
large quantities reported as exports from the wild during the review 
period and because of a lack of information on stocks and management 
activities (CITES 2004b). However, the review did not make any 
conclusions as to the status of T. crocea in Vietnam or whether trade 
was causing negative population level effects.
    Overall, while it appears that some countries have traded T. crocea 
in potentially significant quantities, we could not find any 
information to suggest that these quantities are contributing to the 
overutilization of the species, such that the petitioned action may be 
warranted. Therefore, we conclude that the available information 
presented in the petition and in our files does not constitute 
substantial information that international trade is a significant 
threat posing an extinction risk to T. crocea throughout its range.
    In most locations where information is available, T. crocea does 
not appear to be a highly sought after giant clam species due to its 
small size and burrowing behavior, as these characteristics make it 
more difficult for fishermen to harvest the species. For example, 
Hester and Jones (1974) noted that T. crocea was the only giant clam 
species that did not likely have commercial value in Palau, and that 
the species is seldom utilized for any purpose. bin Othman et al. 
(2010) also generally characterize T. crocea as ``more difficult and 
less economical to harvest'' because this species burrows into 
substrates and is relatively small. In New Caledonia, T. crocea is not 
listed among the preferably harvested species there (Kinch and 
Teitelbaum 2009). As previously discussed in the Population Status and 
Trends section above, Hernawan (2010) attributed T. crocea's relatively 
high population densities in survey sites in Indonesia to the fact that 
Indonesian fishermen do not target this species because of its small 
size and burrowing behavior. This echoes the general characterization 
of commercial utilization of this species by bin Othman et al. (2010). 
Finally, Dolorosa and Shoppe (2005) note that ``T. crocea is little if 
at all exploited'' in the Philippines.
    Overall, most of the information provided in the petition and in 
our files suggest that overutilization is not likely a significant 
threat to T. crocea because its small shell is not economically 
desirable and its burrowing behavior makes it more difficult to harvest 
relative to other species of clams that are much larger in size and 
more easily accessible to fishermen. While it is clear that T. crocea 
fulfills a local market niche and may have experienced historical 
overharvest in Okinawa, Japan, this location represents a very small 
portion of the species' overall range, and we have no additional 
information to suggest that this level of utilization is occurring 
elsewhere, such that the petitioned action may be warranted. 
Additionally, it appears that reseeding efforts and fishing regulations 
have been implemented in Japan to help safeguard giant clam 
populations, including T. crocea, from overfishing. Further, the 
available trade data for T. crocea does not indicate that international 
trade is causing negative population level effects to the species to 
the point that the petitioned action may be warranted. Therefore, we 
conclude that the information in the petition and in our files does not 
constitute substantial information that overutilization is an operative 
threat that acts or has acted on the species to the point that the 
petitioned action may be warranted.
Factor C: Disease or Predation
    The petition did not provide any species-specific information 
regarding how diseases may be affecting T. crocea populations 
throughout its range. In fact, none of the information provided in the 
petition discusses diseases or parasites affecting T. crocea, 
specifically. We could also not find any additional information in our 
files regarding the threats of disease or predation to T. crocea. 
Therefore, we conclude that the petition does not provide substantial 
information that disease or predation is an operative threat that acts 
or has acted on the species to the point that the petitioned action may 
be warranted.
Factor D: Inadequacy of Existing Regulatory Mechanisms
    The petition did not present species-specific information regarding 
inadequate regulatory mechanisms for T. crocea. As discussed above, the 
petitioner notes that there are some laws for giant clams on the books 
in certain locations, but only discusses regulations from the 
Philippines and Malaysia and illegal clam poaching in disputed areas of 
the South China Sea. These areas represent a small portion of the range 
of T. crocea. We found additional regulations in our files regarding 
the harvest of giant clams, including T. crocea, in several countries. 
Numerous PICTs and Australia implement size limits, bag limits, bans on 
commercial harvest, bans on night light harvest, promotion of 
aquaculture, and community-based cultural management systems for giant 
clams (more detail provided above; Chambers 2007; Kinch and Teitelbaum 
2009). For T. crocea specifically, state-set and self-imposed 
regulations prevail in the fishing areas throughout Japan to protect 
the giant clam stock (Okada 1997).
    In terms of trade regulations, the discussion in the petition was 
not species-specific. Additionally, we determined above in the 
Overutilization for Commercial, Recreational, Scientific, or 
Educational Purposes section for T. crocea, that international trade is 
not an operative threat that acts or has acted on the species to the 
point that the petitioned action may be warranted.
    With regard to regulations of greenhouse gas emissions, the 
discussion in the petition was also not species-specific. The 
petitioner did not provide species-specific information regarding the 
negative response to ocean warming or acidification. In addition, the 
information in the petition, and in our files, does not indicate that 
T. crocea may be at risk of extinction that

[[Page 28972]]

is cause for concern due to the loss of coral reef habitat or the 
direct effects of ocean warming and acidification. This is discussed in 
more detail for T. crocea specifically above under Factor A and below 
under Factor E. Therefore, we conclude that the petition does not 
provide substantial information that inadequate regulatory mechanisms 
controlling greenhouse gas emissions is an operative threat that acts 
or has acted on the species to the point that listing may be warranted.
Factor E: Other Natural or Manmade Factors
    Aside from the information previously discussed for giant clams in 
general in the Other Natural or Manmade Factors section, the petition 
did not provide any species-specific information regarding how climate 
change related threats, including ocean warming and acidification, are 
negatively impacting T. crocea populations throughout its range. We 
could also not find any additional information in our files regarding 
these threats to the species. Therefore, we conclude that the 
information presented in the petition and in our files does not 
constitute substantial information that other natural or manmade 
factors, including climate change related threats, acts or has acted on 
the species to the point that the petitioned action may be warranted.
Conclusion
    Based on the foregoing information, we do not agree that the 
petition provides substantial information to indicate that the T. 
crocea may warrant listing as threatened or endangered under the ESA. 
Particularly, in the context of the species' overall range, there is no 
indication that T. crocea has undergone significant population declines 
or local extirpations such that the species' risk of extinction is 
elevated to a point that is cause for concern. In contrast, it is the 
only clam species that is still described as abundant and even dominant 
in many locations where it is found. Given the species' small size and 
unique burrowing behavior, the available information does not indicate 
that T. crocea is highly sought after or targeted by fishermen in most 
locations. Overall, the information presented in the petition and our 
files does not indicate that any identified or unidentified threats may 
be acting on T. crocea to the point that the species may warrant 
listing as threatened or endangered under the ESA. After evaluating the 
population status and threat information presented in the petition and 
in our files in the context of the species' overall range, we conclude 
that the petition did not provide substantial information indicating 
that the petitioned action may be warranted for this species.

Tridacna maxima

Species Description
    The petition provided very little information regarding a general 
description of T. maxima. The petition notes that T. maxima has close-
set scutes and grows to a maximum size of 35 cm. We found additional 
information in our files describing this species. Although maximum 
shell length is 35 cm, it is commonly found at lengths up to 25 cm 
(Kinch and Teitelbaum 2009). Tridacna maxima has a grayish-white shell 
exterior, often suffused with yellow or pinkish orange and strongly 
encrusted with marine growths. The shell interior is porcellaneous 
white, sometimes with yellow to orange hues on the margins. Tridacna 
maxima often has a brightly colored mantle, variable in color and 
pattern (Kinch and Teitelbaum 2009), from brilliant to subdued grayish 
yellow, bluish green, blackish blue, to purple and brown. These colors 
occur medially on the mantle and are sometimes spotted and streaked 
with other colors (Su et al., 2014). The shell of T. maxima usually has 
four to five ribs with round projections on the upper margins (Su et 
al., 2014).
Life History
    The petition presents the majority of life history information for 
T. maxima from Jameson (1976) as cited in Munro (1992). This reference 
studied samples from Guam and reports fecundity (F) of T. maxima as F = 
0.00743 L\3\ (a ripe gonad of a 20 cm specimen would therefore contain 
about 20 million eggs), fertilized eggs of T. maxima had a mean 
diameter of 104.5 [mu]m, and settlement occurred 11 days after 
fertilization at a mean shell length of 195.0 [mu]m. Metamorphosis was 
basically complete about one day after settlement. Jameson (1976) also 
reports that juveniles of T. maxima first acquire zooxanthellae after 
21 days and juvenile shells show the first signs of becoming opaque 
after 47 days. The petition states that male T. maxima in the Cook 
Islands begin to reach sexual maturity at approximately 6 cm; 50 
percent of both males and females were sexually mature at 10 cm and 100 
percent were sexually mature at 14 cm and larger. The species was also 
very slow growing and took 5 years to reach 10 cm in length, 10 years 
to reach 15 cm and 15 to 20 years to reach 20 cm and above. Because 
only 21.5 percent of the population were fully sexually mature, the 
petitioner asserts that overfishing of this species is likely (Chambers 
2007). In Guam and Fiji, T. maxima spawned during the winter months 
(LaBarbera 1975). Findings by Jantzen et al. (2008) suggest T. maxima 
in the Red Sea is a strict functional photoautotroph limited by light.
Range, Habitat, and Distribution
    Among members of the subfamily Tridacninae, T. maxima is the most 
common and widely distributed species in the Indo-Pacific. This species 
ranges from the Red Sea, Madagascar, and East Africa to the Tuamotu 
Archipelago and Pitcairn Island in the South Pacific, as well as from 
southern Japan in the north to Lord Howe Island, off the coast of New 
South Wales, Australia in the south (bin Othman et al., 2010).

[[Page 28973]]

[GRAPHIC] [TIFF OMITTED] TP26JN17.008

    In terms of habitat, T. maxima is a reef-top inhabitant, living on 
the surface of the reef or sand and is usually seen with its colored 
mantle exposed (Su et al., 2014). This species can be found on reefs, 
partially embedded in corals in littoral and shallow water, to a depth 
of 20 m (Kinch and Teitelbaum 2009). In Indonesia, T. maxima was found 
living in dead coral rubble covered in algae, Porites corals, and coral 
rubble (Hernawan 2010).
Population Status and Abundance Trends
    For T. maxima specifically, the petition provides limited 
information regarding the species' population status and trends from 
Singapore and individual sites in Malaysia, the Philippines, Indonesia, 
Thailand, French Polynesia, and the Cook Islands.
    Neo and Todd (2012a) surveyed 87,515 m\2\ in Singapore and did not 
observe T. maxima, despite the observation of one individual in a 2003 
survey of a little over 9,000 m\2\ by Guest et al. (2008). The authors 
acknowledge that no historical abundance data for T. maxima in 
Singapore exist, nor any precise information on their exploitation. 
They go on to propose that habitat loss, exploitation, and/or sediment 
have synergistically led to the extirpation of T. maxima in Singapore's 
waters. Neo and Todd (2013) make a similar conclusion stating that T. 
maxima is ``probably already functionally extinct (in Singapore) as 
they are reproductively isolated and unlikely to fertilise [sic] 
conspecifics.'' However, the authors specifically make the point that 
the status of a species at a small scale (individual country or an 
island as may be the case for Singapore) is not necessarily 
representative of its global status. Any species, especially one with a 
large range like T. maxima, will have variable statuses at smaller 
scales in different habitats due to a variety of factors. Singapore is 
a small and densely populated island nation known for particularly high 
anthropogenic impacts in its nearshore waters. The information in Neo 
and Todd (2012a 2012b and 2013) is informative for resource managers in 
Singapore and indicates a very low population and density of T. maxima. 
However, it is unclear how the current information relates to 
historical abundance of this species at this location. In addition, it 
is not necessarily useful for assessing the global status of T. maxima 
because Singapore is a very small proportion of the overall species' 
range and is not a representative environment of the rest of the 
species' range.
    As described in earlier species accounts, the petitioner cites Tan 
and Yasin (2003), stating giant clams of all species but T. crocea are 
considered endangered in Malaysia. The authors mention underwater 
surveys that reveal that the ``distribution of giant clams are 
widespread but their numbers are very low.'' However, there are no 
references provided by the authors to provide any more detail or 
support for this information, which makes it difficult to interpret 
this information for individual species. The only species-specific 
information for T. maxima in this reference is that it occurs in 
Malaysian waters.
    The petition cites Salazar et al. (1999) who did a stock assessment 
of T. crocea, T. maxima, T. squamosa and H. hippopus in the Eastern 
Visayas of the Philippines and found most of the populations were 
juveniles with insufficient numbers of breeders to repopulate the 
region. As noted previously, this reference was unavailable for review 
so it is unclear if the authors were able to attribute these results to 
environmental changes, overharvest, or some other type of influence.
    As previously discussed in other species accounts, the petition 
states that Hernawan (2010) found small populations and evidence of 
recruitment failure in the six species found during a survey of Kei 
Kecil, Southeast-Maluku, Indonesia, including T. maxima. The author 
conducted giant clam surveys in nine sites; however, Indonesia 
encompasses thousands of islands and T. maxima occurs in other 
locations throughout Indonesia (Hernawan 2010). Thus, this study 
represents a very small sample of T. maxima abundance in Indonesian 
waters, with no evidence provided to suggest that recruitment failure 
of T. maxima is occurring throughout Indonesia.
    The petitioner cites Thamrongnavasawat et al. (2001) as saying T. 
maxima are now considered ``scarce'' throughout Thailand; however the 
link provided in the bibliography to access this reference was not 
functional, and we were otherwise unable to obtain

[[Page 28974]]

and review this reference to determine what the authors meant by 
``scarce'' or on what evidence this statement was based.
    The only references with species-specific information on abundance 
and trends for T. maxima that show evidence for their conclusions are 
from Rose Atoll, two atolls and an island in French Polynesia, and 
Tongareva Lagoon in the Cook Islands. Neo and Todd (2012a) reference 
another study that reports up to 225 T. maxima individuals per square 
meter at Rose Atoll (Green and Craig 1999). The estimated population 
size for Rose Atoll (615ha) was approximately 27,800 T. maxima 
individuals based on surveys from 1994 to 95.
    In French Polynesia, Gilbert et al. (2006) report that several 
lagoons in two archipelagos are characterized by enormous populations 
of T. maxima. They report densities of 23.6 million clams in 4.05 km\2\ 
at Fangatau atoll, 88.3 million clams in 11.46 km\2\ at Tatakoko, and 
47.5 million in 16.3 km\2\ in Tubuai. At the time of publication, the 
authors noted these were the largest giant clam densities observed 
anywhere in the world. The authors also note that a small scale but 
growing fishery in these areas should be actively managed to avoid 
decimating these pristine stocks. They list several existing management 
efforts in French Polynesia including a minimum shell length for 
capture, development of clam aquaculture capacity, and the 
establishment of no-take areas (Gilbert et al., 2006). The first no-
take area dedicated to the conservation of T. maxima was implemented in 
2004 at Tatakoto Atoll, one of the study areas in French Polynesia. Six 
years after the Gilbert et al. (2006) study, a stock assessment survey 
revealed a dramatic decrease in the T. maxima population within the no-
take area and elsewhere throughout the atoll (83 percent overall 
reduction in density), an anomaly the authors attribute to temperature 
variations 3 years prior to the survey, but the cause could not be 
determined definitively (Andrefouet et al., 2013). The authors note 
that mortality events of this scale are not uncommon for bivalves and 
there are other reports of massive die-offs of clams related to 
environmental variables like ENSO-related temperature increases or 
lowered mean sea level in certain areas, which leaves clams exposed to 
unfavorable conditions for long periods. Within a geographic range as 
vast as T. maxima's, one anomalous event that may have been due to 
temperature changes does not constitute substantial information that 
climate change may be affecting the species such that it needs 
protection under the ESA. As noted above in the Threats to Giant Clams 
section, there is huge heterogeneity across space and time in terms of 
current and future impacts of climate change on giant clams species.
    The petition cites Chambers (2007) and notes that T. maxima was 
overharvested in the southern Cook Islands and the capital was now 
receiving them from the northern part of the country, but the specific 
aim of this study was to assess the size distribution, abundance, and 
density of T. maxima in Tongareva lagoon. The author found variation 
within the lagoon with higher densities occurring in the south, farther 
from villages. The overall density recorded was 0.42 clams per square 
meter, with a total population of 28,066 individuals; however, the 
author notes that these numbers were based on extrapolating over the 
whole lagoon, all of which is not necessarily suitable clam habitat. 
The authors suggest that a more accurate extrapolation should be based 
on the area of available suitable habitat to fully account for areas 
where T. maxima occurs in high numbers. While this study indicates some 
areas of lower abundance near population centers (i.e., harvest 
pressure), it also reports high numbers and densities of T. maxima at 
several sites (Chambers 2007).
    Finally, a CITES trade review of T. maxima characterizes the 
species as still reasonably abundant in some countries, being 
``widespread and abundant'' in Australia, and ``common'' with stable 
stocks in Vanuatu (CITES 2004c). Overall, the information regarding 
abundance and population trends for T. maxima is limited, particularly 
given the species' enormous geographic range. As noted previously, any 
species, especially one with a large range like T. maxima, will have 
variable statuses at smaller scales in different habitats due to a 
variety of factors. The limited information in the petition and our 
files, however, does not indicate that T. maxima's overall population 
status or abundance trends are contributing to an elevated extinction 
risk, such that the species may be threatened or endangered throughout 
all or a significant portion of its range.
Threats to T. maxima
Factor A: Present or Threatened Destruction Modification, or 
Curtailment of Range
    The petition asserts that all species of giant clam, including T. 
maxima, are at risk of extinction throughout their ranges due to the 
threat of habitat destruction, largely because of threats related to 
climate change and coral reef habitat degradation. However, the 
petition does not provide any species-specific information regarding 
how habitat destruction is negatively affecting T. maxima. While the 
information in the petition is otherwise [largely] accurate and 
suggests concern for the status of coral reef habitat generally, its 
broadness, generality, and speculative nature, and the lack of 
reasonable connections between the threats discussed and the status of 
T. maxima specifically, means that we cannot find that this information 
reasonably suggests that habitat destruction is an operative threat 
that acts or has acted on the species to the point that the petitioned 
action may be warranted.
Factor B: Overutilization for Commercial, Recreational, or Scientific 
Purposes
    Species-specific information on overharvest of T. maxima in the 
petition is limited. The petitioner cites Bodoy (1984), stating the 
authors found that harvesting decreased the size of T. maxima in Saudi 
Arabia. However, the authors only surveyed four sites with varying 
degrees of accessibility and found that the harder-to-access sites, as 
well as deeper depths at all sites, appear to provide some refuge from 
collection as they observed either more or larger clams (or both) 
there.
    The study by Shelley (1989) discussed above in the Life History 
section documented likely overfishing of T. maxima in the Cook Islands 
based on a very low proportion of mature individuals in the population. 
Chambers (2007) notes that T. maxima was overharvested in the southern 
Cook Islands and the capital was now receiving them from the northern 
part of the country. In the Cook Islands, only cultured clams are 
exported, and wild harvest is for local consumption. Traditional 
cultures in individual villages institute a rahui system to impose 
closures of certain areas for a period of time to allow stocks to 
regenerate (Chambers 2007). While Chambers (2007) indicates some level 
of harvest pressure on T. maxima, they also report areas of high 
numbers and densities of T. maxima in several sites.
    We found additional trade information for T. maxima in some CITES 
documents cited by the petitioner, although the trade information 
therein was not presented in the petition. Out of 31 countries listed 
in a trade review for this species, one was listed as ``Urgent 
Concern'' (Tonga), seven were assessed as ``Possible Concern, and 
``Least Concern'' was reserved for the remaining 23

[[Page 28975]]

countries (CITES 2004c). Countries reported as ``Least Concern'' were 
assessed as such for the following reasons: either there was no trade 
reported over the period under review (1994-2003) (n=10), recorded 
trade during the last 5 years of the period under review was at a low 
level (n=10), or trade was primarily or entirely of captive bred 
specimens.
    Based on the foregoing information, the species-specific 
information presented in the petition and in our files on overharvest 
of T. maxima is not substantial. Given the broad geographic range of 
the species and when considered in combination with all other 
information presented for this species, we find that the petition does 
not provide sufficient information to demonstrate that overutilization 
is an operative threat that acts or has acted on the species to the 
point that the petitioned action may be warranted.
Factor C: Disease or Predation
    The petition does not present any species-specific information 
indicating disease or predation are factors acting on populations of T. 
maxima to the extent that the species may warrant protection under the 
ESA. The generalized information in the petition does not constitute 
substantial information for individual species as discussed above. We 
found some generalized information indicating that T. maxima has some 
known non-human predators (e.g., large triggerfish, octopi, eagle rays, 
and pufferfish) and is vulnerable to predation during the juvenile 
stage (<10 cm); Chambers 2007), but we do not have any additional 
information in our files on the effects of disease or predation on T. 
maxima.
Factor D: Inadequacy of Existing Regulatory Mechanisms
    The petition does not present species-specific information 
regarding inadequate regulatory mechanisms for T. maxima. As discussed 
above, the petitioner notes that there are some laws for giant clams on 
the books in certain locations, but only discusses regulations from the 
Philippines and Malaysia and only discusses illegal clam poaching in 
disputed areas of the South China Sea. These areas represent a small 
portion of the range of T. maxima. We found additional regulations in 
our files regarding the harvest of giant clams in several countries. 
Numerous PICTs and Australia implement size limits, bag limits, bans on 
commercial harvest, bans on night light harvest, promotion of 
aquaculture, and community-based cultural management systems for giant 
clams (more detail provided above in the general Inadequacy of Existing 
Regulatory Mechanisms section of this notice; Chambers 2007; Kinch and 
Teitelbaum 2009).
    In terms of international trade and greenhouse gas regulations, the 
discussion in the petition was again not species-specific. The 
petitioner did not provide species-specific information regarding the 
negative response to ocean warming or acidification. However, we 
evaluated the information in the petition that may apply to all the 
petitioned species. Above in the Threats to Giant Clams section, we 
determined that overall, the entire discussion of the inadequacy of 
CITES is very broad and does not discuss how the inadequacy of 
international trade regulations is impacting any of the petitioned 
species to the point that it is contributing to an extinction risk, 
with the exception of T. gigas and the growing giant clam industry in 
China. In addition, the information in the petition, and in our files, 
does not indicate that the petitioned species may be at risk of 
extinction that is cause for concern due to the loss of coral reef 
habitat or the direct effects of ocean warming and acidification. This 
is discussed in more detail for T. maxima specifically above under 
Factor A and below under Factor E. Therefore, we conclude that the 
petition does not provide substantial information that inadequate 
regulatory mechanisms controlling greenhouse gas emissions is an 
operative threat that acts or has acted on the species to the point 
that the petitioned action may be warranted.
Factor E: Other Natural or Manmade Factors
    The petition presents limited information in terms of other natural 
or manmade factors affecting the status of T. maxima. The petitioner 
cites Waters (2008) who found that T. maxima juveniles exposed to 
pCO2 concentrations approximating glacial (180 ppm), current 
(380 ppm) and projected (560 ppm and 840 ppm) levels of atmospheric 
CO2 (per the IPCC IS92a scenario) suffered decreases in size 
and dissolution with increased levels of atmospheric CO2 and 
this occurred below thresholds previously considered detrimental to 
other marine organisms in similar conditions. We acknowledge these 
results however, they are not easily interpreted into potential species 
level effects over time and/or space for T. maxima. First, the clams 
used in the experiment were cultured and not harvested from the wild. 
Cultured specimens are likely to experience much more uniform 
environments and are likely not acclimated to the common daily 
fluctuations in many environmental parameters experienced in the wild. 
As such, they may react differently than wild specimens to abrupt 
changes in their environment. As discussed in more detail in our 12-
month finding for orange clownfish (80 FR 51235; August 24, 2015), the 
acute nature of the exposure and lack of acclimation in this study is 
noteworthy because most species will not experience changes in 
acidification so acutely in their natural habitats. Rather, they are 
likely to experience a gradual increase in average CO2 
levels over several generations, and therefore a variety of factors 
could come into play over time to aid in adaptation (or may not--there 
is high uncertainty). We recognize that because giant clam species are 
likely long-lived, they likely have longer generation times, and thus, 
giant clams born today could potentially live long enough to experience 
oceanic conditions predicted late this century (Watson et al., 2012). 
However, given the disconnect between these experimental results and 
what can be expected to occur in the wild over time, the uncertainty in 
future ocean acidification rates, and the heterogeneity of the species' 
habitat and current environmental conditions across its large range, 
these results are not compelling evidence that elevated levels of 
atmospheric CO2 is an operative threat that acts or has 
acted on T. maxima to the extent that the petitioned action may be 
warranted.
    The work by Andrefouet et al. (2013) on T. maxima discussed above 
in the section on Population status and Trends documents mortality at 
Tatakoto Atoll in French Polynesia likely due to a temperature anomaly; 
however, again the authors did not definitively identify the cause of 
the observed decline. Further, a single anomaly in one location is not 
indicative of an ongoing threat that contributes to an elevated 
extinction risk for T. maxima. While we acknowledge the potential for 
both ocean warming and ocean acidification to have impacts on T. 
maxima, the petition did not present substantial information indicating 
the species may warrant listing due to these threats, nor do we have 
additional information in our files that would indicate this.
Conclusion
    It is common for all species, especially those with very expansive 
geographic ranges like T. maxima, to experience different impacts and 
variable population statuses throughout different areas within their 
range. In evaluating the information presented in

[[Page 28976]]

the petition, we consider the information itself as well as the scope 
of the information presented as it relates to the range of the species. 
The petition presented species-specific information indicating high 
densities and robust populations in the Cook Islands, French Polynesia, 
and Rose Atoll. It also provided citations with generalized statements 
of rarity of T. maxima in Singapore and individual study sites in 
Malaysia, Indonesia, and Thailand. In the case of T. maxima, areas 
where the species may be in poor status are not compelling evidence of 
the global status of this species compared to its overall range because 
the information is not outside of what is commonly expected in terms of 
variability in species status across such a large range as T. maxima's. 
There is an entire one third or more of the species' range for which no 
information was presented at all in the petition (eastern Africa and 
the Indian Ocean) with the exception of one study from one site in 
Saudi Arabia within the Red Sea. Thus, the petition did not present 
substantial information to indicate either poor population status 
globally or operative threats acting on the species such that the 
petitioned action may be warranted for T. maxima.

Tridacna noae

Species Description
    Tridacna noae, also known as Noah's giant clam, is most like T. 
maxima in appearance, but live T. noae specimens can be distinguished 
by the sparsely distributed hyaline organs, and by the large, easily 
recognizable, ocellate spots with a thin, white contour on the mantle's 
edge (Neo et al., 2015; Su et al., 2014). Shell lengths range between 6 
and 20 cm (Neo et al., 2015).
Life History
    Aside from what has already been discussed in the general life 
history information applicable to all giant clams (refer back to the 
Giant Clam life history section above), the petition did not provide 
any species-specific life history information for T. noae. We could 
also not find any other life history information in our files specific 
to T. noae.
Range, Habitat, and Distribution
    The petition did not provide a range map for this species, nor was 
it included in bin Othman et al. (2010). Tridacna noae's distribution 
overlaps with T. maxima's distribution, but generally occurs in lower 
abundances (Neo et al., 2015). Based on the information provided in the 
petition, T. noae has a widespread distribution across the Indo-
Pacific, occurring from the Ryuku archipelago of Japan to Western 
Australia, and from the Coral Triangle (as defined by Veron et al., 
2009) to the Coral Sea and to the Northern Line Islands (Borsa et al., 
2015b). Tridacna noae is thus known from Taiwan, Japan, Dongsha 
(northern South China Sea), Bunaken (Sulawesi Sea), Madang and Kavieng 
(Bismarck Sea), the Alor archipelago (Sawu Sea), Kosrae (Caroline 
Islands), New Caledonia, the Loyalty Islands and Vanuatu (Coral Sea), 
Viti-Levu (Fiji), Wallis Island, and Kiritimati (Northern Line Islands) 
(Borsa et al., 2015b). Mitochondrial DNA data also indicate its 
presence in the Philippines (eastern Negros), Western Australia (in the 
Molucca Sea at Ningaloo Reef) and in the Solomon Islands (Borsa et al., 
2015b). Individuals are attached by a byssus and bore into coral, 
living in littoral and shallow waters to a depth of 20 m. Borsa et al. 
(2015b) notes that: ``It may occur naturally on the same reef habitats 
as T. maxima, and also T. crocea as reported from the Solomon Islands 
(Huelsken et al., 2013), and as observed at Bunaken and in New 
Caledonia (this survey).''
Population Status and Abundance Trends
    The petition does not provide any species-specific information for 
T. noae concerning its population status or abundance trends. The only 
statement in the petition with regard to T. noae's status and abundance 
is: ``Given the threats discussed elsewhere in this report for Asia and 
here for the South China Sea, it is likely that T. noae has also 
declined severely.'' The petitioner did not provide any references or 
additional supporting information to substantiate this claim. Given 
that the species' geographic range extends far beyond Southeast Asia, 
simply inferring a severe abundance decline throughout the species' 
large geographic range based on generalized threats discussed for one 
part of the range (and without providing any link that these threats 
are specifically acting on T. noae to reduce its abundance) is 
erroneous. Generalized evidence of declining habitat or declining 
populations per se are not evidence of declines large enough to infer 
extinction risk that may meet the definition of either threatened or 
endangered under the ESA. Therefore, we conclude that the information 
presented in the petition on the species' population status and 
abundance trends does not constitute substantial information that the 
species may warrant listing under the ESA. We could also not find any 
information in our files on the population abundance or tends of the 
species.
Threats to Tridacna noae
Factor A: Present or Threatened Destruction, Modification, or 
Curtailment of Its Habitat or Range
    The petition does not provide any species-specific information 
regarding how habitat destruction is negatively impacting T. noae. As 
discussed previously, while the information in the petition is 
otherwise largely accurate and suggests concern for the status of coral 
reef habitat generally, its broadness, generality, and speculative 
nature, and the lack of reasonable connections between the threats 
discussed and the status of T. noae specifically means that we cannot 
find that this information reasonably suggests that habitat destruction 
is an operative threat that acts or has acted on the species to the 
point that the petitioned action may be warranted.
Factor B: Overutilization for Commercial, Recreational, Scientific, or 
Educational Purposes
    Aside from what has already been discussed regarding the threat of 
overutilization for giant clams in general, we could not find any 
species-specific information in the petition or in our files regarding 
overutilization of T. noae for commercial, recreational, scientific, or 
educational purposes. As such, we cannot conclude that the petition 
presented substantial information that overutilization is an operative 
threat that acts or has acted on the species to the point that the 
petitioned action may be warranted.
Factor C: Disease or Predation
    Aside from what has already been discussed regarding the threats of 
disease and predation for giant clams in general (refer back to the 
Threats to Giant Clams section above), we could find no additional 
information regarding disease or predation specific to T. noae. 
Therefore, we conclude that the petition does not provide substantial 
information that disease or predation is an operative threat that acts 
or has acted on the species to the point that the petitioned action may 
be warranted.
Factor D: Inadequacy of Existing Regulatory Mechanisms
    The petition did not present species-specific information regarding 
inadequate regulatory mechanisms for T. noae. As discussed above, the 
petitioner notes that there are some laws for giant clams on the books 
in certain locations, but only discusses regulations from the 
Philippines and Malaysia and

[[Page 28977]]

illegal clam poaching in disputed areas of the South China Sea. These 
areas represent a small portion of the range of T. noae. We found 
additional regulations in our files regarding the harvest of giant 
clams in several countries. Numerous PICTs and Australia implement size 
limits, bag limits, bans on commercial harvest, bans on night light 
harvest, promotion of aquaculture, and community-based cultural 
management systems for giant clams (more detail provided above; 
Chambers 2007; Kinch and Teitelbaum 2009).
    In terms of international trade and greenhouse gas regulations, the 
discussion in the petition was again not species-specific. The 
petitioner did not provide species-specific information regarding the 
negative response to ocean warming or acidification. However, we 
evaluated the information in the petition that may apply to all the 
petitioned species. In the general Threats to Giant Clams section 
above, we determined that overall, the entire discussion of the 
inadequacy of CITES is very broad and does not discuss how the 
inadequacy of international trade regulations is impacting any of the 
petitioned species to the point that it is contributing to an 
extinction risk, with the exception of T. gigas and the growing giant 
clam industry in China. In addition, the information in the petition, 
and in our files, does not indicate that the petitioned species may be 
at risk of extinction that is cause for concern due to the loss of 
coral reef habitat or the direct effects of ocean warming and 
acidification. This is discussed in more detail for T. noae 
specifically above under Factor A and below under Factor E. Therefore, 
we conclude that the petition does not provide substantial information 
that inadequate regulatory mechanisms controlling greenhouse gas 
emissions is an operative threat that acts or has acted on the species 
to the point that the petitioned action may be warranted.
Factor E: Other Natural or Manmade Factors
    Aside from the information previously discussed for giant clams in 
general in the Other Natural or Manmade Factors section, the petition 
does not provide any species-specific information regarding how climate 
change related threats, including ocean warming and acidification, are 
negatively impacting T. noae populations throughout its range. We could 
also not find any additional information in our files regarding these 
threats to the species. As such, we cannot conclude that the petition 
presented substantial information that other natural or manmade 
factors, including climate change related threats, are operative 
threats that act or have acted on the species to the point that the 
petitioned action may be warranted.
Conclusion
    The petition did not provide substantial information that any 
identified or unidentified threats may be acting on T. noae to the 
point that it may warrant listing as threatened or endangered under the 
ESA. We evaluated the extremely limited population status information 
and threat information presented in the petition and in our files and 
cannot conclude that substantial information has been presented that 
indicates the petitioned action may be warranted for this species.
Petition Findings
    Based on the above information and the criteria specified in 50 CFR 
424.14(b)(2), we find that the petition and information readily 
available in our files present substantial scientific and commercial 
information indicating that the petitioned action of listing the 
following giant clam species as threatened or endangered may be 
warranted: H. hippopus, H. porcellanus, T. costata, T. derasa, T. 
gigas, T. squamosa, and T. tevoroa. Therefore, in accordance with 
section 4(b)(3)(A) of the ESA and NMFS' implementing regulations (50 
CFR 424.14(b)(3)), we will commence status reviews of these species. 
During the status reviews, we will determine whether these species are 
in danger of extinction (endangered) or likely to become so within the 
foreseeable future (threatened) throughout all or a significant portion 
of their ranges. We now initiate this review, and thus, we consider 
these giant clam species to be candidate species (69 FR 19975; April 
15, 2004). Within 12 months of the receipt of the petition (August 7, 
2017), we will make a finding as to whether listing these species as 
endangered or threatened is warranted as required by section 4(b)(3)(B) 
of the ESA. If listing these species is found to be warranted, we will 
publish a proposed rule and solicit public comments before developing 
and publishing a final rule. We also find that the petition and 
information readily available in our files do not present substantial 
scientific and commercial information indicating that the petitioned 
action of listing T. crocea, T. maxima, and T. noae is warranted.

Information Solicited

    To ensure that the status reviews are based on the best available 
scientific and commercial data, we are soliciting information relevant 
to whether the giant clam species for which we have made positive 
findings are endangered or threatened. Specifically, we are soliciting 
information in the following areas: (1) Historical and current 
distribution and abundance of these species throughout their respective 
ranges; (2) historical and current population trends; (3) life history 
in marine environments, including growth rates and reproduction; (4) 
historical and current data on the commercial trade of giant clam 
products; (5) historical and current data on fisheries targeting giant 
clam species; (6) any current or planned activities that may adversely 
impact the species; (7) ongoing or planned efforts to protect and 
restore the species and its habitats, including information on 
aquaculture and/or captive breeding and restocking programs for giant 
clam species; (8) population structure information, such as genetics 
data; and (9) management, regulatory, and enforcement information. We 
request that all information be accompanied by: (1) Supporting 
documentation such as maps, bibliographic references, or reprints of 
pertinent publications; and (2) the submitter's name, address, and any 
association, institution, or business that the person represents.

References Cited

    A complete list of references is available upon request to the 
Office of Protected Resources (see ADDRESSES).

    Authority: The authority for this action is the Endangered 
Species Act of 1973, as amended (16 U.S.C. 1531 et seq.).

    Dated: June 21, 2017.
Samuel D. Rauch III,
Deputy Assistant Administrator for Regulatory Programs, National Marine 
Fisheries Service.
[FR Doc. 2017-13275 Filed 6-23-17; 8:45 am]
 BILLING CODE 3510-22-P