[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,
[[Page 28947]]
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.
[[Page 28969]]
[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]
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