[Federal Register Volume 61, Number 201 (Wednesday, October 16, 1996)]
[Proposed Rules]
[Pages 53893-53896]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-26387]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

50 CFR Part 227

[Docket No. 960917262-6262-01; I.D. 122294A]


Listing Endangered and Threatened Species; Shortnose Sturgeon in 
the Androscoggin and Kennebec Rivers, ME

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

ACTION: Denial of petition.

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SUMMARY: NMFS finds that a petitioned action to remove shortnose 
sturgeon (Acipenser brevirostrum) occurring in the Androscoggin and 
Kennebec Rivers from the List of Endangered and Threatened Wildlife is 
not warranted at this time.
    Shortnose sturgeon in the Androscoggin and Kennebec Rivers continue 
to face substantial threats to their habitat and/or range, and existing 
regulatory mechanisms other than the Endangered Species Act (ESA) are 
inadequate to ensure the detailed review and management of these 
threats. Moreover, the Petersen population estimate used by the 
petitioner is higher and less reliable than the best estimate accepted 
by NMFS. The Schnabel population estimate used by NMFS also has 
limitations, but is the best available information upon which a listing 
decision can be based. NMFS lacks critical, recent information on 
population dynamics (e.g., natality, natural mortality, age or size 
structure) that could be used to assess how well the Androscoggin River 
and Kennebec River breeding populations are replacing themselves over 
time.

ADDRESSES: A copy of the Status Review of Shortnose Sturgeon in the 
Androscoggin and Kennebeck Rivers (NMFS, 1996) is available upon 
request to the National Marine Fisheries Service, Office of Protected 
Resources (F/PR), 1315 East-West Highway, Silver Spring, MD, 20910.

FOR FURTHER INFORMATION CONTACT: Marta Nammack, Endangered Species 
Division, NMFS, (301/713-1401).

SUPPLEMENTARY INFORMATION:

Petition Background

    On September 19, 1994, NMFS received a petition from Edwards 
Manufacturing Company, Inc., to remove shortnose sturgeon in the 
Kennebec River system (the Androscoggin and Kennebec Rivers) in 
Kennebec, Sagadahoc and Lincoln Counties, ME, from the List of 
Endangered and Threatened Wildlife (50 CFR 17.11). In support of its 
petition, petitioner cited research conducted on shortnose sturgeon in 
the Androscoggin and Kennebec Rivers over the last two decades and an 
initial population estimate averaging 11,000 adult shortnose sturgeon. 
Additionally, density data (shortnose sturgeon per hectare) reported 
from six river populations, including the Kennebec River, were used to 
infer that, at least, the Kennebec River system was supporting a 
shortnose sturgeon population near carrying capacity.
    On January 6, 1995, NMFS issued a 90-day finding (60 FR 2070) that 
the petition presented substantial information indicating that the 
petitioned action may be warranted. NMFS initiated a status review of 
shortnose sturgeon occurring within the Androscoggin and Kennebec 
Rivers and, using the best scientific and commercial data available, 
assessed whether shortnose sturgeon inhabiting the Androscoggin and 
Kennebec Rivers could be delisted as requested by the petitioner.
    When originally listed, shortnose sturgeon were considered 
endangered throughout their range in the eastern United States, though 
not all extant populations were identified at the time of their 
original listing. Today, at least 17 populations of shortnose sturgeon 
are known within the species' wide latitudinal range. Recognizing that 
the knowledge concerning shortnose sturgeon increased during the years 
following the species' ESA listing, NMFS began a status review in the 
late 1980s to assess whether individual shortnose sturgeon populations 
should be considered ``distinct'' for ESA purposes.1 Further, the 
status review was also used to investigate changes to the listing 
status of these individual populations in instances where changes 
appeared warranted. In the 1987 status review, NMFS stated that:
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    \1\ In the 1978 amendments to the ESA, the definition of 
``species'' was changed to: ``any subspecies of fish or wildlife or 
plants, and any distinct population segment of any species of 
vertebrate fish or wildlife which interbreeds when mature.''

    the differences reported in longevity, growth rates, and age at 
sexual maturity between shortnose sturgeon from the northern and 
southern extremes of its range are expected in any species with a 
wide latitudinal distribution. The best available information also 
indicates differences in life history and habitat preferences 
between the northern and southern river systems

[[Page 53894]]

(Dadswell et al., 1984) although available genetic and morphometric 
data do not support any taxonomic splitting of the species. However, 
given the species' anadromous breeding habits, it is unlikely that 
populations in adjacent river systems interbreed with any 
regularity. Therefore, until interbreeding is confirmed, we will 
consider each population within a river system to be a distinct unit 
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under the ESA definition of ``species.''

    The 1987 status review also indicated that the listing status of 
the shortnose sturgeon population in the Kennebec River system 
(including the Androscoggin River) should be re-evaluated and that 
available information indicated that the ``population'' in the Kennebec 
and Androscoggin Rivers may no longer require protection under the ESA. 
This suggestion was met with disagreement in the scientific community 
in comments NMFS received on the status review. Therefore, a team of 
NMFS biologists and other scientists from state and private agencies 
was convened to critically review the 1987 status review and assess the 
merits of the listing recommendations contained within the status 
review. However, the team did not complete its task, and no changes to 
the listing status of shortnose sturgeon populations were proposed.
    Section 4(a) of the ESA mandates that the Secretary of Commerce 
determine whether a species is an endangered or threatened species 
because of any of the following factors: (A) The present or threatened 
destruction, modification, or curtailment of its habitat or range; (B) 
overutilization for commercial, recreational, or scientific, or 
educational purposes; (C) disease or predation; (D) the inadequacy of 
existing regulatory mechanisms; or (E) other natural or manmade factors 
affecting its continued existence. NMFS, in determining whether to 
delist a species, must consider the same five factors.

Status as a ``Species'' Under the ESA

    In response to this petition, NMFS conducted a peer-reviewed status 
review of shortnose sturgeon in the Androscoggin and Kennebec Rivers to 
determine if the populations inhabiting these rivers were separate DPSs 
under the ESA definition of ``species.'' That report, ``Status Review 
of Shortnose Sturgeon in the Androscoggin and Kennebec Rivers (NMFS, 
1996),'' is available upon request (see ADDRESSES). Significant 
findings described in the status review, as they pertain to this 
petition finding, are summarized below.
    Shortnose sturgeon occur in the estuarine complex formed by the 
Androscoggin, Kennebec, and Sheepscot Rivers. The Maine Department of 
Marine Resources (MDMR) began studying sturgeon in the Kennebec and 
Androscoggin Rivers in 1977 to determine the distribution and abundance 
of adults of the species. The MDMR conducted a pooled adult population 
estimate for the Androscoggin and Kennebec Rivers using the Petersen 
and Schnabel population size estimators (Krebs, 1989). These estimates 
involve marking and recapturing fish and incorporate similar 
assumptions about the population, though the calculations differ in 
slight but significant ways. The NMFS and the MDMR agree that the 
Schnabel estimate is more reliable than the Petersen estimate for a 
multiple census-based population estimate. Although the two estimates 
are point estimates derived from 15-year-old data, these data provide 
the best available information on the distribution and abundance of 
adult shortnose sturgeon occurring in the Kennebec and Androscoggin 
River systems.
    Based on the joint NMFS/U.S. Fish and Wildlife Service (USFWS) 
policy regarding the recognition of DPSs under the ESA (61 FR 4722, 
February 7, 1996), the following criteria are considered in determining 
the status of a possible DPS under the ESA: (1) Discreteness of the 
population segment in relation to the remainder of the species to which 
it belongs; (2) the significance of the population segment in relation 
to the remainder of the species to which it belongs; and (3) the 
population's conservation status in relation to ESA standards for 
listing (i.e., is the population segment, when treated as if it were a 
species, endangered or threatened?). These three criteria are discussed 
briefly below and in more detail in the status review.

Discreteness

    To be discrete, a sturgeon population must be markedly separated 
from other populations of the same taxon as a consequence of physical, 
physiological, ecological, or behavioral factors, or be delimited by 
international boundaries. Quantitative measures of genetic or 
morphological discontinuity may provide evidence for this separation. 
Waples (1991) and NMFS (56 FR 58612, November 20, 1991) provided 
guidance for determining the ``discreteness'' and evolutionary 
significance of Pacific salmon populations. This guidance was used to 
develop the current policy on DPSs that applies to all vertebrates. In 
making a determination of population distinctness under the ESA, Waples 
(1991) recommends, as a first step, considering whether a population is 
substantially isolated reproductively from other conspecific 
populations.
    Shortnose sturgeon populations show a high degree of reproductive 
isolation (Dadswell, 1976; Dadswell et al., 1984). Ocean captures of 
shortnose sturgeon are extremely rare, and straying rates between 
stocks, though unmeasured, appear to be very low, based on the lack of 
recaptures of tagged fish in adjacent rivers. Given this pattern, which 
seems to predominate more in the northern portion of the sturgeon's 
range, some authors have suggested that ``amphidromy'' (limiting 
migrations to natal estuaries) best describes the shortnose sturgeon's 
life history pattern (Bain, in press; Kynard, in press). Squiers et al. 
(1981) captured fish in spawning condition in the Androscoggin and 
Kennebec Rivers in May of 1980 and 1981. This information indicates 
that each river supports spawning populations of shortnose sturgeon, 
though it does not provide conclusive evidence for river-specific 
spawning stocks. However, there is ample evidence from other, well-
studied sturgeon populations to support a trend of river-specific 
spawning (Buckley and Kynard, 1985; Dadswell et al., 1984; Dovel, 1981; 
O'Herron et al., 1992). Based on this information, and to be 
biologically conservative with respect to stock discreteness, NMFS 
considers shortnose sturgeon populations in the Androscoggin and 
Kennebec Rivers likely to be reproductively separate, and, therefore, 
discrete populations.

Significance

    With such limited information on the biology and ecology of either 
population and the habitats occupied by shortnose sturgeon in both 
systems, NMFS is unable to assess the biological or ecological 
significance of either population segment independently. Although the 
populations in question may meet the first criterion of a DPS 
(discreteness), there are not enough biological data currently 
available to classify each population as a DPS. Therefore, NMFS' 1987 
decision to combine the Androscoggin and Kennebec River populations as 
a single distinct unit, for ESA purposes, is consistent with the 
current DPS policy. NMFS refers to this DPS as the Androscoggin/
Kennebec Rivers DPS comprised of the Androscoggin and Kennebec River 
breeding populations. Further studies may reveal significant 
differences and, if warranted at a future time, necessitate separate 
DPS listings for both the Androscoggin River and Kennebec River 
populations.

[[Page 53895]]

Conservation Status in Relation to ESA Standards for Listing

    The most reliable population estimate for shortnose sturgeon in the 
Androscoggin and Kennebec Rivers DPS is the composite Schnabel 
estimate: An average of 7,222 with a 95 percent confidence interval of 
5,046 to 10,765 (Squiers et al., 1981). This is considered to reflect a 
combined population of adult shortnose sturgeon that spawn throughout 
the Androscoggin/Kennebec Rivers DPS. Shortnose sturgeon are known to 
spawn in cycles, and estimates indicate that adults may spawn at 
intervals of 3 years (Dovel, 1981; Dadswell et al., 1984). Thus, of 
this group of potential spawners, only one third are expected to spawn 
each year (Dovel, 1981; Boreman, 1992). Using the adult population 
estimates obtained by the MDMR, the range of census adult population 
sizes is 1,682 to 3,588 fish, one-third of the total adult population 
size or the number of annually spawning fish. This range reflects a 
combined estimate for adult fish inhabiting both the Androscoggin and 
Kennebec Rivers (the breeding populations constituting the 
Androscoggin/Kennebec DPS). The estimate of the subpopulation in each 
river is unknown. Potentially, shortnose sturgeon in one of these 
rivers may be persisting at extremely low levels.
    NMFS also examined indices of catch-per-unit effort, length/age 
frequencies, and other types of data to evaluate the breeding 
populations in the Androscoggin/Kennebec Rivers DPS. Catch-per-unit 
effort has increased in the Androscoggin River (Squiers et al., 1993), 
and may be viewed as a positive indication that this population was 
recruiting successfully in the early 1980s. A current population 
estimate, using similar capture methodology to that in the previous 
estimate, could be used to confirm this. NMFS does not have adequate 
length frequency data for either the Androscoggin or Kennebec Rivers to 
construct age or size-structured population models for each breeding 
population. This severely impedes NMFS' ability to assess the listing 
status of Androscoggin/Kennebec Rivers DPS. Section 4(b)(1) of the ESA 
requires that all decisions to list, change the status of, or delist a 
species be based on the best scientific and commercial data available.
    Using the Petersen population estimate of 10,000 fish in the 
Androscoggin and Kennebec Rivers, the petitioner cited calculations of 
average density (shortnose sturgeon per hectare) to infer that the 
Kennebec River shortnose sturgeon population is ``at or near carrying 
capacity regarding available food production.'' This conclusion is 
unfounded because the Petersen population estimate used by the 
petitioner to derive density estimates is questionable because it was 
not based on a statistically reliable sample size and it relied on a 
faulty methodology and inaccurate statistical assumptions (NMFS, 1996). 
NMFS considers the Schnabel estimate of 7,222 fish to be the best 
estimate of the adult segment of the populations comprising both the 
Androscoggin and Kennebec Rivers. Also, NMFS lacks critical information 
about current river-specific population sizes and shortnose sturgeon 
population dynamics in the Androscoggin and Kennebec Rivers to assess 
density-dependent and density-independent factors that might lead to an 
estimate of carrying capacity. Finally, the petitioner's estimate of 
hectares of bottom habitat is not a direct measure of prey density. 
Without knowledge that suitable habitat exists for shortnose sturgeon 
(i.e., that it is adequate for reproduction, foraging, and 
overwintering), an estimate of bottom surface area is not meaningful.
    The petitioner also cited Dadswell et al. (1984) to support the 
assertion that sturgeon densities are high with respect to available 
bottom habitat. However, Dadswell et al. (1984) point out that making 
assumptions about total population sizes from discrete estimates of 
foraging population sizes is not sound:

    Population size projections, for rivers with poorly known 
populations, that use densities calculated for feeding 
concentrations rather than average densities * * * are 
inappropriate.

    The Petersen estimate cited was derived from an average of nine 
mark-recapture estimates that were concentrated on the summer feeding 
grounds of adult shortnose sturgeon.
    NMFS' ``Status Review of Shortnose Sturgeon in the Androscoggin and 
Kennebec Rivers'' (NMFS, 1996) analyzed the five listing factors from 
section 4(a) of the ESA and reached the following conclusions: (1) 
Shortnose sturgeon in the Androscoggin and Kennebec Rivers continue to 
face substantial threats to their habitat and/or range due to 
hydroelectric facilities, channel dredging, and the introduction of 
pollutants via sewage treatment plants, paper mills, and other 
industrial facilities; (2) overutilization of shortnose sturgeon for 
commercial, recreational, scientific, or commercial purposes is not 
currently a threat in the Androscoggin and Kennebec Rivers, but 
pressure for commercial utilization could increase if the species were 
removed from protected status; (3) the influence of disease or 
predation on shortnose sturgeon in the Androscoggin and Kennebec Rivers 
has not been investigated; (4) existing regulatory mechanisms other 
than the ESA limit the direct harvest of shortnose sturgeon but are 
inadequate to ensure the detailed review of potentially damaging 
construction activities that are closely scrutinized through the ESA 
Section 7 consultation process; and (5) NMFS is not aware of any other 
natural or anthropogenic factors affecting shortnose sturgeon survival 
in the Androscoggin and Kennebec Rivers DPS.
    Documented recovery criteria for shortnose sturgeon populations do 
not currently exist, although the NMFS Shortnose Sturgeon Recovery Team 
established in 1992 is presently drafting a Shortnose Sturgeon Recovery 
Plan that will include such criteria. In the absence of these criteria, 
and as a supplement to NMFS' analysis of the five ESA listing factors, 
NMFS used interim criteria from the conservation biology literature to 
evaluate the status of shortnose sturgeon populations in the 
Androscoggin and Kennebec Rivers. This additional information is 
discussed in the ``Status Review of Shortnose Sturgeon in the 
Androscoggin and Kennebec Rivers (NMFS, 1996).''

Determination

    NMFS finds that the petitioned action to delist shortnose sturgeon 
in the Androscoggin and Kennebec Rivers is not warranted at this time. 
Based on the factors specified in the ESA to guide listing decisions, 
NMFS concludes that shortnose sturgeon in the Androscoggin and Kennebec 
Rivers DPS continue to face substantial threats to their habitat and/or 
range and that existing regulatory mechanisms other than the ESA are 
inadequate to ensure the detailed review and management of these 
threats. The potential of habitat modification or direct takes of 
shortnose sturgeon to impede the recovery of the species in the 
Androscoggin and Kennebec Rivers warrants serious consideration before 
any changes are made in the species' listing status.
    Moreover, the Petersen population estimate used by the petitioner 
is higher and less reliable than the best (Schnabel) estimate accepted 
by NMFS. Even if the Petersen population estimate was accepted, NMFS 
lacks critical, recent information on population dynamics (e.g., 
natality, natural mortality, age or size structure) needed to assess 
how well the Androscoggin River and Kennebec River breeding

[[Page 53896]]

populations are replacing themselves over time.
    In consideration of the DPS definition for shortnose sturgeon, NMFS 
concludes that available data are insufficient to warrant designating 
the individual populations in the Androscoggin River and Kennebec River 
as DPSs (species) under the ESA. Therefore, as first determined in 
NMFS' 1987 status review, NMFS views shortnose sturgeon in the 
Androscoggin and Kennebec Rivers as a single DPS comprised of at least 
two local breeding populations. Future studies may reveal significant 
differences and, if warranted, necessitate separate DPS listings for 
the Androscoggin River and Kennebec River populations.

    Dated: October 9, 1996.
Rolland A. Schmitten,
Assistant Administrator for Fisheries, National Marine Fisheries 
Service.
[FR Doc. 96-26387 Filed 10-15-96; 8:45 am]
BILLING CODE 3510-22-F