Endangered and Threatened Wildlife and Plants; Final Listing Determinations for Two Distinct Population Segments of Atlantic Sturgeon (Acipenser oxyrinchus oxyrinchus, 5914-5982 [2012-1950]

Agencies

• DEPARTMENT OF COMMERCE
• National Oceanic and Atmospheric Administration

[Federal Register Volume 77, Number 24 (Monday, February 6, 2012)]
[Rules and Regulations]
[Pages 5914-5982]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2012-1950]



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Vol. 77

Monday,

No. 24

February 6, 2012

Part III





Department of Commerce





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 National Oceanic and Atmospheric Administration





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50 CFR Part 224





Endangered and Threatened Wildlife and Plants; Final Listing 
Determinations for Two Distinct Population Segments of Atlantic 
Sturgeon (Acipenser oxyrinchus oxyrinchus) in the Southeast; Final Rule

Federal Register / Vol. 77, No. 24 / Monday, February 6, 2012 / Rules 
and Regulations

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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

50 CFR Part 224

[Docket No. 090219208-1762-02]
RIN 0648-XN50


Endangered and Threatened Wildlife and Plants; Final Listing 
Determinations for Two Distinct Population Segments of Atlantic 
Sturgeon (Acipenser oxyrinchus oxyrinchus) in the Southeast

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

ACTION: Final rule.

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SUMMARY: We, NMFS, issue a final determination to list the Carolina and 
South Atlantic distinct population segments (DPSs) of Atlantic sturgeon 
(Acipenser oxyrinchus oxyrinchus) as endangered under the Endangered 
Species Act (ESA) of 1973, as amended. We have reviewed the status of 
the species and conservation efforts being made to protect the species, 
considered public and peer review comments, and we have made our 
determination that the Carolina and South Atlantic DPSs are in danger 
of extinction throughout their ranges, and should be listed as 
endangered, based on the best available scientific and commercial data.

DATES: This final rule is effective April 6, 2012.

ADDRESSES: Assistant Regional Administrator for Protected Resources, 
NMFS, Southeast Regional Office, 263 13th Avenue South, St. Petersburg, 
FL 33701-5505.

FOR FURTHER INFORMATION CONTACT: Kelly Shotts, NMFS, Southeast Regional 
Office (727) 824-5312 or Lisa Manning, NMFS, Office of Protected 
Resources (301) 427-8466.

SUPPLEMENTARY INFORMATION:

Background

    We first identified Atlantic sturgeon as a candidate species in 
1991. On June 2, 1997, NMFS and U.S. Fish and Wildlife Service (USFWS; 
collectively, the Services) received a petition from the Biodiversity 
Legal Foundation requesting that we list Atlantic sturgeon in the 
United States, where it continues to exist, as threatened or endangered 
and designate critical habitat within a reasonable period of time 
following the listing. A notice was published in the Federal Register 
on October 17, 1997, stating that the Services had determined 
substantial information existed indicating the petitioned action may be 
warranted (62 FR 54018). In 1998, after completing a comprehensive 
status review, the Services published a 12-month determination in the 
Federal Register announcing that listing was not warranted at that time 
(63 FR 50187; September 21, 1998). We retained Atlantic sturgeon on the 
candidate species list (and subsequently transferred it to the Species 
of Concern List (69 FR 19975; April 15, 2004)). Concurrently, the 
Atlantic States Marine Fisheries Commission (ASMFC) completed Amendment 
1 to the 1990 Atlantic Sturgeon Fishery Management Plan (FMP) that 
imposed a 20- to 40-year moratorium on all Atlantic sturgeon fisheries 
until the Atlantic Coast spawning stocks could be restored to a level 
where 20 subsequent year classes of adult females were protected 
(ASMFC, 1998). In 1999, pursuant to section 804(b) of the Atlantic 
Coastal Fisheries Cooperative Management Act (ACFCMA) (16 U.S.C. 5101 
et seq.), we followed this action by closing the Exclusive Economic 
Zone (EEZ) to Atlantic sturgeon retention. In 2003, we sponsored a 
workshop in Raleigh, North Carolina, with USFWS and ASMFC entitled, 
``The Status and Management of Atlantic Sturgeon,'' to discuss the 
status of sturgeon along the Atlantic Coast and determine what 
obstacles, if any, were impeding their recovery. The workshop revealed 
mixed results in regards to the status of Atlantic sturgeon riverine 
populations, despite the coastwide fishing moratorium. Some populations 
seemed to be recovering while others were declining. Bycatch and 
habitat degradation were noted as possible causes for continued 
population declines.
    Based on the information gathered from the 2003 workshop on 
Atlantic sturgeon, we decided that a new review of Atlantic sturgeon 
status was needed to determine if listing as threatened or endangered 
under the ESA was warranted. The Atlantic sturgeon status review team 
(ASSRT), consisting of four NMFS, four USFWS, and three U.S. Geological 
Survey (USGS) biologists prepared a draft status review report. The 
draft report was then reviewed and supplemented by eight state and 
regional experts who provided their individual expert opinions on the 
scientific facts contained in the report and provided additional 
information to ensure the report provided the best available data. 
Lastly, the report was peer reviewed by six experts from academia. A 
Notice of Availability of the final status review report was published 
in the Federal Register on April 3, 2007 (72 FR 15865). On October 6, 
2009, we received a petition from the Natural Resources Defense Council 
to list Atlantic sturgeon as endangered under the ESA. As an 
alternative, the petitioner requested that the species be delineated 
and listed as the five DPSs described in the 2007 Atlantic sturgeon 
status review report (ASSRT, 2007): Gulf of Maine, New York Bight, 
Chesapeake Bay, Carolina, and South Atlantic DPSs, with the Gulf of 
Maine and South Atlantic DPSs listed as threatened, and the remaining 
three DPSs listed as endangered. The petitioner also requested that 
critical habitat be designated for Atlantic sturgeon under the ESA. We 
published a Notice of 90-Day Finding on January 6, 2010 (75 FR 838), 
stating that the petition presented substantial scientific or 
commercial information indicating that the petitioned actions may be 
warranted. On October 6, 2010, we published a proposed rule (75 FR 
61904) to list the Carolina and South Atlantic DPSs, the two DPSs that 
spawn in the NMFS Southeast Region, as endangered. We originally 
solicited written public comments via email, fax, and letter on the 
proposed listing rule for 90 days and extended it for an additional 30 
days by public request. We also accepted written and verbal comments at 
two public hearings in Wilmington, North Carolina, and Atlanta, 
Georgia, in December 2010. A separate proposed rule (75 FR 91872) was 
published on October 6, 2010, for the three DPSs of Atlantic sturgeon 
that spawn in the NMFS Northeast Region.

Listing Determinations Under the Endangered Species Act

    We are responsible for determining whether Atlantic sturgeon are 
threatened or endangered under the ESA (16 U.S.C. 1531 et seq.). To be 
considered for listing under the ESA, a group of organisms must 
constitute a ``species,'' which is defined in section 3 of the ESA to 
include ``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.'' On February 7, 1996, the 
Services adopted a policy describing what constitutes a DPS of a 
taxonomic species (61 FR 4722). The joint DPS policy identified two 
elements that must be considered when identifying a DPS: (1) The 
discreteness of the population segment in relation to the remainder of 
the species (or subspecies) to which it belongs; and (2) the 
significance of the population segment to the remainder of the species 
(or subspecies) to which it

[[Page 5915]]

belongs. As stated in the joint DPS policy, Congress expressed its 
expectation that the Services would exercise authority with regard to 
DPSs sparingly and only when the biological evidence indicates such 
action is warranted.
    Section 3 of the ESA defines an endangered species as ``any species 
which is in danger of extinction throughout all or a significant 
portion of its range'' and a threatened species as one ``which is 
likely to become an endangered species within the foreseeable future 
throughout all or a significant portion of its range.'' The statute 
requires us to determine whether any species is endangered or 
threatened as a result of any one or a combination of the following 
five factors: (A) The present or threatened destruction, modification, 
or curtailment of its habitat or range; (B) overutilization for 
commercial, recreational, 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 (section 4(a)(1)(A)(E)). Section 4(b)(1)(A) of the 
ESA requires us to make listing determinations based solely on the best 
scientific and commercial data available after conducting a review of 
the status of the species and after taking into account efforts being 
made to protect the species. Accordingly, we have followed a stepwise 
approach in making our listing determination for Atlantic sturgeon. 
Considering biological evidence, such as the separation between river 
populations during spawning and the possibility of multiple distinct 
interbreeding Atlantic sturgeon populations, we evaluated whether 
Atlantic sturgeon population segments met the DPS Policy criteria. We 
then determined the status of each DPS (each ``species'') and 
identified the factors and threats contributing to their status per 
section 4(a)(1) of the ESA. Finally, we assessed efforts being made to 
protect the species, determining if these efforts are adequate to 
mitigate impacts and threats to the species' statuses. We evaluated 
ongoing conservation efforts using the criteria outlined in the Policy 
for Evaluating Conservation Efforts (PECE; 68 FR 15100; March 28, 2003) 
to determine their certainties of implementation and effectiveness.
    Finally, section 4(b)(1)(B) of the ESA requires us to give 
consideration to species which: (1) Have been designated as requiring 
protection from unrestricted commerce by any foreign nation or pursuant 
to an international agreement; or (2) have been identified as in danger 
of extinction, or likely to become so within the foreseeable future, by 
any state agency or by any agency of a foreign nation.

Peer Review and Public Comments

    In December 2004, the Office of Management and Budget (OMB) issued 
a Final Information Quality Bulletin for Peer Review establishing 
minimum standards for peer review. Similarly, a joint NMFS/FWS policy 
(59 FR 34270; July 1, 1994) requires us to solicit independent expert 
review from at least three qualified specialists. We solicited peer 
review comments on the proposed listing rule from three peer reviewers, 
two from academia and one from a Federal resource agency, with 
expertise on Atlantic sturgeon. Written public comments were received 
from 59 commenters and 7 commenters provided verbal comments at the 
public hearings. Peer review comments are treated in the next section. 
In the following sections of the document, the public comments are 
categorized in the following areas: (1) The delineation of DPSs; (2) 
abundance and trends; (3) differences between the proposed rule and the 
conclusions in the 2007 and 1998 status reviews; (4) the need to list 
Atlantic sturgeon under the ESA and consequences of listing; (5) the 
analysis of threats (habitat modification and destruction, 
overutilization, disease and predation, the inadequacy of regulatory 
mechanisms, other natural and manmade factors); (6) recovery; (7) 
critical habitat; and (8) adequacy of the public hearing. Many comments 
were complex and had multiple inferences, and thus individual 
statements are addressed in multiple comments and responses below. 
Information and data provided by commenters supported or did not 
conflict with our findings for the Carolina and South Atlantic DPSs. 
Some information submitted by commenters as ``new'' information was 
information already included and evaluated in our proposed listing rule 
determination. Some commenters asked us to consider information, such 
as increased compliance responsibilities and economic costs on agencies 
and the public, that the ESA and its implementing regulations prohibit 
us from considering in making listing determinations. Many commenters 
stated that NMFS should postpone a listing determination until the 
results of recent research are available, further research can be 
undertaken, state and Federal moratoria on the harvest and possession 
of Atlantic sturgeon have been in effect for the full planned duration, 
and/or until non-listing alternatives (e.g., entering into multi-agency 
partnerships and expanding existing programs) have been explored. 
Because we were petitioned to list the Atlantic sturgeon, we cannot 
delay an assessment of the status of Atlantic sturgeon. We were 
required to evaluate the status of the species and the threats it is 
currently facing and make a finding on whether the petitioned action 
was warranted within 12 months, which resulted in our proposed listing 
determination of endangered for the Carolina and South Atlantic DPSs of 
Atlantic sturgeon. We believe the current body of information on the 
declines of Atlantic sturgeon, the failure of their population numbers 
to rebound despite harvest prohibitions, and the ongoing impacts from 
bycatch, habitat modification, and the inadequacy of existing 
regulatory mechanisms or protective efforts to control or mitigate for 
these impacts, warrant listing the Carolina and South Atlantic DPSs as 
endangered. The information provided in the peer review and public 
comments did not provide a basis for revising our evaluation of the 
status of Atlantic sturgeon, the nature and significance of the threats 
and impacts they face, or our listing determinations. In the following 
sections of the document, we summarize the comments pertaining to the 
proposed listing rule for the Carolina and South Atlantic DPSs and 
provide our responses to those comments. Complete copies of the peer 
review comments, the written public comments, and transcripts of the 
public hearings are available on the Internet at www.regulations.gov.

Peer Review Comments

    In this section, we refer to peer reviewers 1, 2, and 3, which 
correspond to the way the peer reviewers are identified on https://www.regulations.gov.
    Comment 1 (definitions of endangered and threatened): Two of the 
three peer reviewers disagreed, all or in part, with our proposed 
listing of the Carolina and South Atlantic DPSs as endangered. Each 
peer reviewer provided their own definitions of endangered and 
threatened.
    Peer reviewer 1 believed that a DPS warranted an endangered listing 
only if no single historical spawning river within the DPS sustained an 
abundant and regularly reproducing Atlantic sturgeon population. Peer 
reviewer 1 stated that no substantive biological justification or new 
evidence is presented in the proposed listing of the Carolina and South 
Atlantic DPSs as endangered to change the conclusions presented in the 
2007 status review, which concluded that the Carolina DPS should be 
listed as threatened and made

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no conclusion with regard to the South Atlantic DPS due to lack of 
information to allow a full assessment of subpopulations within the 
DPS. Peer reviewer 1 stated that an endangered listing would be 
appropriate if no single historical spawning river within that DPS 
appeared to sustain both a relatively abundant and simultaneously 
regularly-reproducing Atlantic sturgeon population.
    Based on the available information on abundance, reproduction, and 
the presence of early life history stages, the reviewer stated that the 
Carolina DPS comes closest to conforming to the standard of an 
endangered species. The reviewer cited data from the proposed listing 
rule that two of the original three major spawning populations (the 
Roanoke and Santee-Cooper populations) in the Carolina DPS appear to 
remain functional, and not particularly vulnerable to extinction. The 
reviewer also stated the proposed listing of the South Atlantic DPS did 
not appear to be supported by the best available scientific 
information, since there is evidence of at least one viable, 
reproducing, and increasing Atlantic sturgeon population in the South 
Atlantic DPS, the Altamaha River population (Schueller and Peterson, 
2006, 2010). The reviewer further cited both the Savannah River and the 
ACE (Ashepoo, Combahee, and Edisto Rivers) Basin systems as appearing 
to support reproducing Atlantic sturgeon populations, and stated 
Atlantic sturgeon appear to be abundant in the ACE system. The reviewer 
questioned whether the remaining South Atlantic DPS river populations 
in the smaller and less well-studied Ogeechee and Satilla rivers 
together constitute a significant portion of the species' range over 
which extinction is probable in order to justify an ``endangered'' 
designation for the entire DPS. The reviewer noted that the 2007 status 
review report deferred from such a designation and that it appears the 
South Atlantic DPS does not closely conform to the standard of being 
endangered. Based on the available scientific evidence concerning 
population size and reproduction in the historically most important 
populations, the resilience of sturgeons to extirpation, and their 
capacity for re-population from small effective population size, the 
reviewer believed the appropriate ESA designation for both DPSs would 
seem to be threatened. The reviewer suggested that the threatened 
status would provide protection for the species from direct take of any 
kind and a basis for habitat restoration, while providing greater 
flexibility for scientific sampling, tissue analyses, and experimental 
manipulation than would endangered status. The reviewer stated the 
downside is that threatened status would provide a lower level of legal 
leverage relative to the larger industrial impacts, e.g., dams and 
bycatch, either of which may represent an insurmountable impasse to 
sturgeon recovery. The reviewer offered that under existing direct 
harvest prohibitions, threatened status has worked effectively for Gulf 
sturgeon recovery in rivers where dams and bycatch are not significant 
issues. It has not worked effectively where dams and bycatch are 
significant issues (e.g., the Pearl, Pascagoula, and Apalachicola 
rivers), although none of those populations seem in danger of 
extinction.
    Peer reviewer 2 stated that implicit in the definition of 
``endangered'' is that the species must be on a significant downward 
trend, or at least there is cause to believe that such a trend is 
happening now, or will happen soon, and concluded that is not the case 
on the Altamaha River in Georgia. However, this reviewer also commented 
that every single Atlantic sturgeon population has been decimated by 
overfishing and habitat degradation and that we have very little 
quantified evidence that the species as a whole has recovered, despite 
14 years of the protection afforded under the current moratorium on 
harvest and possession. Peer reviewer 2 recommended that a 
``threatened'' listing would seem appropriate for almost every Atlantic 
coast river, including the St. Marys, Satilla, Ogeechee, and Savannah 
Rivers in Georgia, with the Altamaha being the one exception, and an 
endangered listing would be difficult to support.
    Response: We must rely on the definition of ``endangered'' and 
``threatened'' species provided in section 3 of the ESA, the 
implementing regulations, and case law in applying the definitions to 
marine and anadromous species. Section 3 of the ESA defines an 
endangered species as one that is in danger of extinction throughout 
all or a significant portion of its range, and a threatened species as 
one that is likely to become endangered within the foreseeable future. 
Recent case law (In Re Polar Bear Endangered Species Act Listing and 
Sec.  4(d) Rule Litigation, D.D.C. WL 2601604 (June 30, 2011 Order); 
748 F.Supp.2d 19 (D.D.C. 2010)) regarding USFWS's listing of the polar 
bear as threatened provides a thorough discussion of the ESA's 
definitions and the Services' broad discretion to determine on a case 
by case basis whether a species is in danger of extinction. Upon 
listing the polar bear as threatened, USFWS's rule was challenged by a 
number of parties who claimed that the polar bear was in danger of 
extinction and should have been listed as endangered, and by others who 
conversely argued that the bear did not warrant listing even as 
threatened. The Court determined that neither the ESA nor its 
legislative history compels the interpretation of ``endangered'' as a 
species being in ``imminent'' risk of extinction, finding instead that 
the phrase ``in danger of extinction'' is ambiguous. The Court held 
that there is a temporal distinction between endangered and threatened 
species in terms of the proximity of the ``danger'' of extinction, 
noting that the definition of ``endangered species'' is phrased in the 
present tense, whereas a threatened species is ``likely to become'' so 
in the future. Thus, in the context of the ESA, the Services interpret 
an ``endangered species'' to be one that is presently at risk of 
extinction. A ``threatened species,'' on the other hand, is not 
currently at risk of extinction, but is likely to become so. In other 
words, a key statutory difference between a threatened and endangered 
species is the timing of when a species may be in danger of extinction, 
either now (endangered) or in the foreseeable future (threatened). The 
Court concluded, however, that the distinction is not based ``solely 
and unambiguously'' on the imminence of the species' anticipated 
extinction,'' and that Congress delegated responsibility to the 
Services to determine whether a species is presently `in danger of 
extinction' in light of the five ESA section 4(a)(1) factors and the 
best available science for that species. The Court ruled that although 
imminence of harm is clearly one factor that the Services weigh in 
their decision-making process, it is not necessarily a limiting factor. 
In many cases, the Services might appropriately find that the imminence 
of a particular threat is the dispositive factor that warrants listing 
a species as `threatened' rather than `endangered,' or vice versa. The 
Services have broad discretion to decide that other factors outweigh 
the imminence of the threat. In conclusion, the Court confirmed that 
the Services have flexibility to determine ``endangerment'' on a case-
by-case basis. Congress did not intend to make any single factor 
controlling when drawing the distinction between endangered and 
threatened species, nor did it seek to limit the applicability of the 
endangered

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category to only those species facing imminent extinction.
    Thus, contrary to the peer reviewers' comments, there is no per se 
requirement that a species be experiencing current or imminent 
significant downward trends, or that there are no single historical 
spawning river populations within the DPSs that are relatively abundant 
and simultaneously regularly-reproducing, in order to be listed as 
endangered (we discuss the status and data on the Altamaha River 
population in more detail in Comment 2 below). Our determination of 
endangerment for the Carolina and South Atlantic DPSs is based on the 
exercise of our expert professional judgment on the basis of the best 
available information for each DPS. In addition, we agree with the 
USFWS' judgment, discussed in its supplemental explanation filed in the 
polar bear litigation, that to be listed as endangered does not require 
that extinction be certain or probable, and that it is possible for a 
species validly listed as ``endangered'' to actually persist 
indefinitely.
    We determined that the Carolina and South Atlantic DPSs of Atlantic 
sturgeon are currently in danger of extinction throughout their ranges, 
on the basis of precipitous declines to population sizes, the 
protracted period in which sturgeon populations have been depressed, 
the limited amount of current spawning, and the impacts and threats 
that have and will continue to prevent population recovery. Populations 
of Atlantic sturgeon declined precipitously decades ago due to directed 
commercial fishing. The failure of Atlantic sturgeon numbers within the 
Carolina and South Atlantic DPSs to rebound even after the moratorium 
on directed fishing was established in 1998 indicates that impacts and 
threats from limits on habitat for spawning and development, habitat 
alteration, and bycatch are responsible for the risk of extinction 
faced by both DPSs. In addition, the persistence of these impacts and 
threats points to the inadequacy of existing regulatory mechanisms to 
address and reduce habitat alterations and bycatch. As described in the 
proposed listing rule, the Carolina DPS is estimated to number less 
than 3 percent of its historical population size; the South Atlantic 
DPS is estimated to number less than 6 percent of its historical 
population size, with all river populations except the Altamaha 
estimated to be less than 1 percent of historical abundance. There are 
an estimated 343 adults that spawn annually in the Altamaha River and 
less than 300 adults spawning annually (total of both sexes) in the 
river systems where spawning still occurs for each DPS (not all of the 
river systems occupied by the two Southeast DPSs currently support 
spawning, or effective spawning leading to recruitment).
    In light of threats and impacts, the low population numbers of 
every river population in the Carolina and South Atlantic DPSs suggests 
that the DPSs are currently in danger of extinction throughout their 
ranges; none of the populations are large or stable enough to alone or 
in combination provide any level of certainty for continued existence 
of either DPS, and thus, the peer reviewer's suggestion that these DPSs 
may not be endangered rangewide or in a significant portion of their 
ranges is erroneous. While the directed fishery that originally 
drastically reduced the numbers of Atlantic sturgeon has been closed, 
recovery of depleted populations is an inherently slow process for a 
late-maturing species such as Atlantic sturgeon, and they continue to 
face a variety of other threats that contribute to their risk of 
extinction. Their late age at maturity (5 to 19 years in the Southeast) 
provides more opportunities for individual Atlantic sturgeon to be 
removed from the population before reproducing. While a long life-span 
also allows multiple opportunities to contribute to future generations, 
it increases the timeframe over which exposure to the multitude of 
threats facing the Carolina and South Atlantic DPS can occur.
    Based on available information, we determined that to be viable, 
the Carolina and South Atlantic DPSs require multiple stable riverine 
populations, and we have added discussion to the final determination to 
better explain our reasoning. The importance of having multiple stable 
riverine spawning populations within each DPS and the need to maintain 
suitable habitat to support the various life functions (spawning, 
feeding, growth) of Atlantic sturgeon is best understood by looking at 
the concept of metapopulations. Each DPS, made up of multiple river 
populations, is analogous to a metapopulation, which is a ``population 
of populations'' (Levins, 1969), a group of spatially separated 
populations of the same species which interact at some level. 
Separation into metapopulations is expected by sturgeon and other 
anadromous fishes. While recolonization of northern rivers following 
post-Pleistocene deglaciation likely occurred following a stepping-
stone sequential model (Waldman et al., 2002), genetic analyses reveal 
that currently, there are very low rates of exchange between river 
populations. The amount and effectiveness of movement separates a 
metapopulation from a single large, patchy population. Low rates of 
connectivity through dispersal, with little to no effective movement, 
allow individual populations to remain distinct as the rate of 
migration between local populations is low enough not to have an impact 
on local dynamics or evolutionary lineages and distinguishes a 
metapopulation from a patchy population (Harrison 1994).
    Metapopulation persistence depends on the balance of extinction and 
colonization in a static environment (Hanski 1996). If habitat remains 
suitable following local extirpation, recolonization via immigrants 
into now-empty habitat may replace at least some of those losses 
(Thomas, 1994). However, if the cause of extinction is a deterministic 
population response to unsuitable conditions (e.g., lack of suitable 
spawning habitat, poor water quality, or disturbance of substrates 
through repeated dredging), the local habitat is likely to remain 
unsuitable after extinction and be unavailable for effective 
recolonization (Thomas, 1994). Therefore, recolonization is dependent 
upon both immigration from adjacent, healthy populations and habitat 
suitability. Because the DPSs are groups of populations, the stability, 
viability, and persistence of individual populations affects the 
persistence and viability of the larger DPS. The loss of any population 
within a DPS will result in: (1) A long-term gap in the range of the 
DPS that is unlikely to be recolonized, or recolonized only very 
slowly; (2) loss of reproducing individuals; (3) loss of genetic 
biodiversity; (4) potential loss of unique haplotypes; (5) potential 
loss of adaptive traits; and (6) reduction in total number. The loss of 
a population will negatively impact the persistence and viability of 
the DPS as a whole as fewer than two individuals per generation 
currently spawn outside their natal rivers (Wirgin et al., 2000; King 
et al., 2001; Waldman et al., 2002).
    The persistence of individual populations, and in turn the DPS, 
depends on successful spawning and rearing within the freshwater 
habitat, the immigration into marine habitats to grow, and then the 
return of adults to natal rivers to spawn. Information on Atlantic 
sturgeon spawning within the Carolina and South Carolina DPSs is 
limited. In the proposed listing rule, we presumed spawning was 
occurring if young-of-the-year (YOY) were observed or mature adults 
were present in freshwater portions of the system.

[[Page 5918]]

Within the Carolina DPS, we concluded that spawning is occurring, or 
occurred in the recent past, in the following rivers based on these 
data:
    1. Roanoke River--collection of 15 YOY (1997-1998); single YOY 
(2005).
    2. Tar and Neuse Rivers--one YOY (2005).
    3. Cape Fear--upstream migration of adults in the fall, carcass of 
ripe female upstream in mid-September.
    4. Winyah Bay--running ripe male in Great Pee Dee River (2003).
    Within the South Atlantic DPS, we concluded that spawning is 
occurring, or has occurred in the recent past, in the following rivers 
based on these data:
    1. ACE Basin--1,331 YOY (1994-2001); gravid female and running ripe 
male in the Edisto (1997); 39 spawning adults (1998).
    2. Savannah River--22 YOY (1999-2006); running ripe male (1997).
    3. Ogeechee River--age-1 captures, but high inter-annual 
variability (1991-1998); 17 YOY (2003); 9 YOY (2004).
    4. Altamaha River--74 captured/308 estimated spawning adults 
(2004); 139 captured/378 estimated spawning adults (2005).
    5. Satilla River--4 YOY and spawning adults (1995-1996).
    These data indicate that spawning occurs within the Carolina and 
South Atlantic DPSs; they do not indicate the frequency of annual 
spawning events or the degree to which spawning in these systems leads 
to population growth, persistence, or viability. The extent and 
effectiveness of spawning events is unknown and likely precarious in 
many rivers, given ongoing threats that limit population size and 
spawning success, such as water quality and restricted access to 
upstream spawning areas (75 FR 61904). Peer reviewer 1 stated that data 
from the proposed listing rule indicate the spawning populations in the 
Santee-Cooper system appear to remain functional and not particularly 
vulnerable to extinction; however, in the proposed listing rule, we 
noted our determination that spawning may occur in the Santee and/or 
the Cooper Rivers, but it may not result in successful recruitment. 
Lack of access to historical spawning habitat due to dams restricts 
spawning to areas just below the dam. The proximity of these spawning 
areas to salt water may result in very high mortality to any larvae 
spawned in those systems.
    In addition to spawning success, it is difficult to quantify 
spawning potential within the two DPSs, given the lack of population 
estimates. Currently, the number of Atlantic sturgeon in the Carolina 
DPS is estimated to be 3 percent of historical population size and the 
South Atlantic DPS is estimated to be 1 percent of historical 
population size, with the exception of the Altamaha River population, 
estimated to be at 6 percent of historical population size. Although 
the largest impact that caused the precipitous decline of the species 
has been curtailed (directed fishing), the population size has remained 
relatively constant at these greatly reduced levels for approximately 
100 years.
    In response to comments about divergence from the status review 
report's listing conclusions for the Carolina and South Atlantic DPSs, 
NMFS' Protected Resources Divisions have the responsibility to make 
listing recommendations to the Assistant Administrator. Status review 
reports are an important part of the information base for such 
recommendations, but NMFS must independently review the information in 
status review reports and apply the ESA's listing determination 
requirements in accordance with regulations, case law, and agency 
guidance. The Atlantic Sturgeon Status Review Report states that 
``risks of extinction assessments are performed to help summarize the 
status of the species, and do not represent a decision by the Status 
Review Team on whether the species should be proposed for listing as 
endangered or threatened under the ESA'' (page 106; ASSRT, 2007). 
Subsequent to the status review report, we conducted a comprehensive 
assessment of the combined impact of the five ESA section 4(a)(1) 
factors across the Carolina and South Atlantic DPSs in classifying 
extinction risk for each DPS. We focused on evaluating whether the DPSs 
are presently in danger of extinction or the danger of extinction is 
likely to develop in the future. In our proposed rules to list 5 DPSs 
of Atlantic sturgeon, we determined that each DPS was at greater risk 
of extinction than determined by the 2007 ASSRT. While the ASSRT did 
discuss and consider how multiple threats might act in concert on a 
given subpopulation, they ultimately classified extinction risk using 
the highest single threat score on an individual population within a 
DPS, or within what they considered to be a significant portion of a 
DPS's range (pages 108-109; ASSRT, 2007). We evaluated the overall 
stability and viability of the DPSs as a whole based on the combined 
statuses of the component river populations and the impacts of threats 
and impacts across the DPS, when determining extinction risk of each 
DPS, because, as discussed above, the Carolina and South Atlantic DPSs 
require multiple stable river populations. In addition, because of the 
lapse in time between the development of the status review report 
(ASSRT, 2007) and the publication of the proposed listing rule (75 FR 
61904, October 6, 2010), new information on bycatch (ASMFC, 2007) and 
water quality (USEPA, 2008), as well as climate change (IPCC, 2008) and 
drought (e.g., USGS, 2007), became available to us, and we incorporated 
this information into our listing determinations.
    Since publication of the proposed rules, a Federal District Court 
has thoroughly reviewed and considered the distinction between the 
definitions of threatened and endangered species in the ESA, explained 
by the USFWS in litigation challenging their determination to list the 
polar bear as threatened and not endangered, as discussed above (In re. 
Polar Bear Endangered Species Act Litigation). Prompted by this 
decision and the comments received by the Services requesting further 
explanation of the divergence of our proposed listing statuses and the 
conclusions of the ASSRT, we have reviewed our determinations and 
concluded that all the proposed listings of specific DPSs as 
``threatened species'' or ``endangered species,'' respectively, satisfy 
the requirements of the relevant ESA definition. Thus, we have not 
changed these classifications in the final rules. We found that the 
Carolina and South Atlantic DPSs are presently in danger of extinction, 
and thus, listing them as endangered is warranted.
    As discussed above, because a DPS is a group of populations (a 
metapopulation), the stability, viability, and persistence of 
individual populations affects the persistence and viability of the 
larger DPS. The persistence of individual populations, and in turn the 
DPS, depends on successful spawning and rearing within the freshwater 
habitat, the immigration into marine habitats to grow, and then the 
return of adults to natal rivers to spawn. While the directed fishery 
that originally drastically reduced the numbers of Atlantic sturgeon 
has been closed, modification and curtailment of Atlantic sturgeon 
habitat resulting from dams, dredging, and degraded water quality are 
inhibiting spawning and population rebounding throughout both DPSs, and 
contributing to their endangered statuses. Existing water allocation 
issues will likely be compounded by human population growth and 
potentially by climate change as well. Climate change is predicted to 
elevate water temperatures and exacerbate nutrient-loading,

[[Page 5919]]

pollution inputs, and lower dissolved oxygen (DO), all of which are 
currently negatively impacting the Carolina and South Atlantic DPSs. 
Continued overutilization of Atlantic sturgeon from bycatch in multiple 
commercial fisheries in both their marine and freshwater habitats is 
another ongoing impact to the Carolina and South Atlantic DPSs that is 
contributing to their endangered status. Atlantic sturgeon taken as 
bycatch may suffer immediate mortality. In addition, stress or injury 
to Atlantic sturgeon taken as bycatch but released alive may result in 
increased susceptibility to other threats, such as poor water quality 
(e.g., exposure to toxins and low DO). This may result in reduced 
ability to perform major life functions, such as foraging and spawning, 
or may even result in post-capture mortality. Several of the river 
populations in the South Atlantic DPS (e.g., the Ogeechee and the 
Satilla) are stressed to the degree that any level of bycatch could 
have an adverse impact on the status of the DPS (ASSRT, 2007).
    The Carolina and South Atlantic DPSs are in danger of extinction 
now, due to precipitous declines from historical abundances to 
population sizes that are low and potentially unstable throughout the 
DPSs. As discussed above, both DPSs exhibit sporadic spawning with 
uncertain effectiveness. Population rebuilding and recovery in both 
DPSs is being inhibited by impacts due to habitat curtailment and 
degradation, and due to capture as bycatch in commercial fisheries. The 
current low levels of abundance noted previously in combination with 
the high degree of threat to the two Southeast DPSs put them in danger 
of extinction throughout their ranges; none of the populations making 
up the DPSs are large or stable enough to provide any level of 
certainty for continued existence of either DPS.
    Regarding the conclusion that the Carolina and South Atlantic DPSs 
should be listed as threatened, peer reviewer 1 incorrectly stated that 
listing as threatened provides protection from direct take of any kind. 
The ESA's prohibition against take contained in section 9 only applies 
to endangered species, unless a section 4(d) rule is in place to extend 
the take prohibition to a threatened species. If we determine that the 
Carolina and South Carolina DPSs meet the ESA's definition of 
endangered, then we cannot list the species as threatened for the 
purposes of providing flexibility for scientific sampling, tissue 
analyses, and experimental manipulation. We also cannot list the DPSs 
as endangered to obtain legal leverage relative to the larger 
industrial impacts, e.g., dams and bycatch, as suggested by the 
reviewer. Rather, we must make our listing determination based on 
application of the statutory factors.
    Comment 2 (new information on Altamaha River population): Peer 
reviewer 2 presented data on the estimated abundance of age-1, river 
resident Atlantic sturgeon in the Altamaha River from 2004 to 2010, 
which showed large estimated increases in this age group in 2009 and 
2010. The peer reviewer also stated that he and other researchers are 
beginning to detect slower growth in age-1 Atlantic sturgeon in the 
Altamaha and he attributed this to density-dependent factors that are 
beginning to limit available resources. The reviewer stated that a few 
more years of data are needed to determine if the increasing trend is 
real, but none of the other variables tested (e.g., river flows or 
temperature) explain the trend. The peer reviewer attributed the 
apparent increases in juveniles in the Altamaha to the moratorium on 
the harvest of adults. The peer reviewer stated that data are not 
available to determine whether this trend is occurring in other 
spawning populations. The reviewer stated that catch per unit effort 
(CPUE) data are worthless without calibration or validation and we do 
not have historical abundance data to know what abundance should be on 
any of the river systems, though there is general agreement that 
populations are a fraction (less than 1 to 10 percent) of historical 
abundance. The reviewer recommended that long-term monitoring of 
recruitment using mark-recapture of age-1 juveniles be implemented on 
key river systems.
    Response: We are encouraged by the apparent increases in juvenile 
Atlantic sturgeon estimated by the peer reviewer's research in the 
Altamaha River and appreciate the contribution of this information for 
our consideration in our listing determination. We revised the relevant 
discussion in the text from the proposed listing rule to include this 
information. We agree that additional years of data are necessary to 
confirm this trend in the Altamaha and that we cannot determine whether 
similar trends may be occurring in other river populations. This 
information is consistent with information we provided in the proposed 
listing rule, which refers to the Altamaha River as having a larger and 
healthier Atlantic sturgeon population than any other river in the 
Southeast. The proposed listing rule also stated that juvenile Atlantic 
sturgeon from the Altamaha are relatively more abundant in comparison 
to other rivers in the region.
    Peer reviewer 2 noted that density-dependent factors may be 
starting to limit available resources. We are interested in working 
with the reviewer and other researchers to determine whether habitat 
modification, which we describe in detail in the proposed listing rule, 
is a contributing factor to the limitation of resources in addition to 
the increase in numbers of juvenile Atlantic sturgeon utilizing the 
resources. While water quality in the Altamaha River is good at this 
time, the drainage basin is dominated by silviculture and agriculture, 
with two paper mills and over two dozen other industries or 
municipalities discharging effluent into the river. Nitrogen and 
phosphorus concentrations are increasing, and eutrophication and loss 
of thermal refugia are growing concerns for this and other rivers in 
the South Atlantic DPS. The Altamaha is one of the rivers with current 
and pending water allocation issues. We are currently funding a project 
through the ESA section 6 program to map habitats in four Georgia 
rivers, including the Altamaha, and this may be a valuable step in 
answering this question.
    We agree that CPUE data should be used in the proper context and 
that historical abundance data, other than data from commercial 
fisheries in the late 19th century, are not available. However, as 
required by section 4(b)(1)(A) of the ESA, we must make our listing 
determination based on the best scientific and commercial data 
available. When only CPUE and other fishery-dependent data were 
available to us, we clarified and acknowledged the constraints of the 
data, and we conclude that we used them in a valid manner. This is 
further addressed in our responses to several public comments on 
specific sections of the proposed listing rule (e.g., comments 19, 23, 
24, 25, and 29).
    Comment 3 (import of the 2003 workshop): Peer reviewer 1 stated the 
proposed listing rule appeared to dismiss any evidence of an increase 
in Carolina DPS populations of Atlantic sturgeon, citing a statement in 
the proposed listing rule (page 61904-61905) that ``the [NMFS-sponsored 
2003] workshop revealed mixed results in regards to the status of 
Atlantic sturgeon populations, despite the coast-wide fishing 
moratorium. Some populations seemed to be recovering while others were 
declining.'' The reviewer stated that at the time of the 2003 workshop, 
the moratorium on direct harvest and possession of Atlantic sturgeon 
had only been in effect for 4 years and this was not sufficient time 
for populations to increase in response

[[Page 5920]]

to the protective measures. The reviewer concluded the observations 
available at the time of the 2003 workshop do not provide a scientific 
basis for listing the Carolina DPS as endangered.
    Response: The information we evaluated in making our proposed 
listing determination of endangered for the Carolina and South Atlantic 
DPSs of Atlantic sturgeon was not confined to the results of the 2003 
workshop. As stated in the proposed listing rule, the information 
gathered at the 2003 workshop, including the equivocal evidence that 
some populations appeared to be recovering while others were declining, 
prompted us to complete a new review of Atlantic sturgeon status, which 
was published in 2007. Since the ASSRT's completion of its status 
review, we obtained and evaluated additional information on threats to 
Atlantic sturgeon (see our response to comment 1). Our evaluation of 
this information indicates that the moratorium on directed fisheries 
has not and will not be sufficient to address the impacts that are 
preventing sturgeon populations from recovering (including lack of 
access to required habitat, and habitat quality issues). Section 
4(b)(1)(A) of the ESA stipulates that listing decisions be made using 
the best available scientific and commercial information, therefore we 
used information from the 2007 status review report (which incorporated 
information from the 2003 workshop) and new information in forming our 
determination. Our responses to comments from the public further detail 
our use of information available at the time of the proposed listing 
rule, as well as our consideration of new information submitted during 
the public comment period.
    Comment 4 (viability of small Atlantic sturgeon populations): The 
estimated 343 spawning adult Atlantic sturgeon in the Altamaha River 
exceeds the number of spawning adults in the ``very viable'' Yellow 
River Gulf sturgeon population, according to peer reviewer 1. Peer 
reviewer 1 stated that information presented in Schueller and Peterson 
(2010) suggests a very robust reproductive response to protection of 
adult spawners under the Atlantic sturgeon moratorium. From these data, 
the reviewer stated that it seems highly improbable that the Altamaha 
River population is at risk of extinction and a listing of endangered 
does not seem applicable to the Altamaha population within the South 
Atlantic DPS. The reviewer stated that if the Altamaha population 
follows the model of the Suwannee River Gulf sturgeon population after 
harvest was banned, then overall population growth in the next decade 
will be exponential until density-dependent population controls come 
into play. Peer reviewer 1 also stated that the ``less than 300 
spawning adults'' criterion in the proposed listing rule for 
classifying a river population as vulnerable to extinction sets a 
``very high, probably unrealistic, bar,'' and one not conforming to 
scientific literature documenting sturgeon population recovery from 
much smaller effective breeding population sizes (20-80 spawning 
females, based on examples provided by the reviewer). Peer reviewer 1 
stated that sturgeon species have the documented ability to establish/
re-establish viable populations over a short timeframe (10 to 20 
years), starting from ``a few tens'' of spawning adults without 
negative fitness impacts from low genetic diversity.
    Response: As explained above, NMFS does not agree with peer 
reviewer 1's premise that an endangered listing would only be 
appropriate if no single historical spawning river within that DPS 
appeared to sustain both a relatively abundant and simultaneously 
regularly-reproducing Atlantic sturgeon population. We note that the 
Yellow River population of Gulf sturgeon referred to as ``very viable'' 
by the reviewer is listed as threatened under the ESA. While the number 
of spawning adult Atlantic sturgeon in the Altamaha River may be larger 
than that of Gulf sturgeon in the Yellow River, the peer reviewer noted 
that the Yellow River population is one that has rebounded since it was 
listed. The Altamaha River population of Atlantic sturgeon is estimated 
to be at only 6 percent of its historical abundance. While there is a 
moratorium on harvest and possession of Atlantic sturgeon, the species 
is not currently afforded the protections of section 9 of the ESA, nor 
do they benefit from the consultation and permitting responsibilities 
of ESA sections 7 and 10, that apply to the listed Gulf sturgeon. 
Information provided by peer reviewers 1 and 2 indicated recent (2009-
2010) increases in the estimated number of juveniles in the Altamaha 
River. We are encouraged by this and hope that the Altamaha River 
population does exhibit exponential growth, as the Suwannee River Gulf 
sturgeon population did following listing. However, our listing 
determination is based on the best information currently available to 
us, and we do not feel that the information provided on increases in 
juvenile Atlantic sturgeon in the Altamaha River or the comparison to 
Gulf sturgeon populations in the Suwannee and Yellow Rivers provides a 
basis for revising our proposed determination that the South Atlantic 
DPS be listed as endangered.
    In response to the reviewer's comment that the ``less than 300 
spawning adults criterion'' sets a ``very high, probably unrealistic, 
bar'', we clarify that the 300 spawning adults per year was an estimate 
of the relative sizes of Atlantic sturgeon river spawning populations, 
based on the available information on the annual spawning adult 
abundance measured in the Altamaha River (343 spawning adults) and the 
fact that it is the largest population in the Southeast, combined with 
qualitative and quantitative anecdotal information from the other river 
systems. The 300 spawning adults per year estimate does not constitute 
a criterion or a bar for listing and/or recovery as a general matter. 
Rather, the estimate is evaluated in the specific context of the 
Atlantic sturgeon river populations and the impacts and threats they 
face. These populations likely have the capacity to recover, as the 
reviewer suggested, if existing and future impacts and threats are 
alleviated. The low estimated population numbers in each of the river 
systems within the DPSs (1-6 percent of historical abundance), combined 
with the ongoing impacts and threats from habitat modification and 
bycatch, indicate that the populations are small and vulnerable, and 
the DPSs they comprise are in danger of extinction.
    Comment 5 (sturgeon ability to recolonize systems; genetic 
exchange): Peer reviewer 1 stated that sturgeon species are resilient 
and capable of repopulating an extirpated river, or colonizing a new 
river, if habitat remains available, dams do not block spawning ground 
access, water quality is satisfactory, and a competing sturgeon 
population is not already established. A natal river population, well-
established over a long span of geological time and highly adapted to 
its respective natal river, would not realize success in colonizing 
another river already populated by a second population better adapted 
to its respective natal river than a potential colonist. The reviewer 
stated that the low rate of genetic exchange displayed among adjacent 
sturgeon populations does not reflect the incapacity of the species to 
colonize, but the competitive advantage held by a pre-established natal 
river population facing migrant individuals. The reviewer provided 
examples of recolonization by Atlantic sturgeon in bays and rivers from 
New England to Labrador and Newfoundland within a span of 10,000 years 
following deglaciation. The

[[Page 5921]]

reviewer stated the northernmost and most genetically conservative 
Atlantic sturgeon population re-colonized over 1,500 miles of coastline 
within 40 generations (and probably much fewer) in addition to 
undertaking a successful, essentially instantaneous, 3,300 mile 
migration to colonize the Baltic Sea 1,200 years ago. The reviewer also 
provided an example of Gulf sturgeon rebounding in Gulf Coast river 
systems. Peer reviewer 1 stated that following state harvest 
prohibitions on the Gulf sturgeon and its listing as threatened under 
the ESA, some river populations have rebounded (the Yellow, 
Choctawhatchee, and Suwannee river populations). The reviewer concluded 
the logic in the proposed listing rule is not compelling that if one of 
the DPSs were to be completely extirpated, it would remain so over a 
long span of time. Peer reviewer 3 stated, in reference to the genetic 
analyses showing fewer than two individuals per generation spawn 
outside their natal rivers, that this reflects the average number of 
individuals and noted it would be useful to compare this to straying 
determined from tagging data.
    Response: We agree with the peer reviewer's comment that the low 
rate of genetic exchange displayed between Atlantic sturgeon river 
populations may reflect the competitive advantage held by pre-
established natal river populations facing migrant individuals. We 
revised the relevant discussion in the text from the proposed listing 
rule to include this information. However, as stated in the proposed 
listing rule, we do not expect Atlantic sturgeon that originate from 
other river systems to recolonize extirpated systems and establish new 
spawning populations, except perhaps over a long time frame (i.e., many 
Atlantic sturgeon generations). Though the reviewer provided an example 
of Atlantic sturgeon colonizing the Baltic Sea 1,200 years ago after a 
single migration, other examples of recolonization provided took 40 
generations (approximately 1,000 years, based on a 25-year generation 
period) to 10,000 years, which is consistent with our statement in the 
proposed listing rule. Further, recolonization occurred in the absence 
of present-day human impacts, such as habitat modifications and 
mechanized fishing.
    We noted the reviewer's comment that sturgeon species are resilient 
and capable of repopulating an extirpated river or colonizing a new 
river if habitat remains available, dams do not block spawning ground 
access, and water quality is satisfactory. As discussed extensively in 
the proposed listing rule and in our responses to comments in this 
document, Atlantic sturgeon in the Carolina and South Atlantic DPSs and 
the rivers within their ranges are affected by habitat modification and 
destruction, blocked access to spawning grounds, downstream habitat 
impacts caused by dams, and water quality (and quantity) issues. Thus, 
the commenter's stated conditions for expecting recolonization by 
Atlantic sturgeon are not met. Atlantic sturgeon from the Carolina and 
South Atlantic DPSs are also taken as bycatch in fisheries. Regarding 
the statement that following state harvest prohibitions on the Gulf 
sturgeon and its listing as threatened under the ESA, some river 
populations have rebounded (the Yellow, Choctawhatchee, and Suwannee 
river populations), the rivers that have rebounded have two factors in 
common versus those which have not rebounded (e.g., the Apalachicola, 
Pascagoula, and Pearl river populations): (1) No mainstem dam on the 
natal river limiting Gulf sturgeon access to upriver spawning grounds 
or YOY access to riverine feeding habitat; and, (2) no major commercial 
fishery causing Gulf sturgeon bycatch mortality in the natal river, 
natal river estuary, or adjacent marine waters. Assessing the impacts 
of these two factors may be equally as important to sturgeon population 
recovery as is protection from all other impacts, now that direct 
harvest has been stopped. We agree with these comments by the peer 
reviewer and also believe that these threats associated with dams, 
habitat, water quality, and bycatch would hamper and slow 
recolonization of extirpated river systems. One reviewer acknowledged 
that rivers, watersheds, and coastal habitats inhabited by Atlantic 
sturgeon have been drastically modified and impacted by human 
activities (dammed, channelized, de-watered, diverted, dredged, mined, 
sedimented, polluted, deforested, developed, populated by introduced 
species, etc.) and that it would be remarkable to achieve recovery to 
even 10-30 percent of the 1890 carrying capacity of individual sturgeon 
rivers.
    In reference to peer reviewer 3's suggestion about comparing the 
degree of straying from tagging studies to the estimate of straying 
from the genetic studies, we agree this could be a valuable exercise in 
the future when we have the necessary information on river of origin 
(based on genetic analyses) and the degree of straying (from tagging 
and relocation studies). While the estimate of less than 2 individuals 
spawning in rivers outside their natal system is a measure of 
successful transfer of genetic information from a fish originating from 
another system, the analysis suggested by the peer reviewer would 
provide us with knowledge of how many fish actually stray into another 
system and potentially attempt to spawn. This could also provide 
insight into the comments by the first peer reviewer that lack of gene 
flow between river populations is due to reduced success from 
competition and not from lack of attempts at migrant spawning.
    Comment 6 (issues with estimating sturgeon abundance): According to 
one peer reviewer, targeted Atlantic sturgeon population studies in the 
Roanoke River and Santee-Cooper system, as well as most other river 
systems, have been limited in duration, intensity, and continuity such 
that population estimates may be substantially underestimated. Peer 
reviewer 1 noted that sturgeon species are cryptic fish found in deep, 
mainstem rivers. They are rarely observed visually, not typically 
sampled in many commercial river fisheries targeting other fish species 
(with the exception of the shad gill net fishery), and are rarely 
caught by recreational anglers. The reviewer stated that this 
illustrates that presence and abundance of sturgeon cannot be based on 
incidental catches from commercial fisheries or scientific sampling not 
specifically targeting sturgeon. The reviewer stated that in the past, 
sturgeon abundance has often been vastly underestimated until an 
appropriate and dedicated reporting or sampling program was undertaken. 
The reviewer recommended that only continuous, standardized mark-
recapture efforts spanning sufficient time (a minimum of 3 years, but 
realistically greater than 5 years) can provide reliable preliminary 
abundance estimates.
    Response: The majority of the data presented in the proposed 
listing rule came from studies targeting Atlantic sturgeon or from 
fisheries that are known to have a high incidence of interaction with 
Atlantic sturgeon (i.e., gillnet fisheries). As much as possible, we 
clarified the data collection methods and constraints, and any 
assumptions we made. This is also discussed in our response to comment 
2. We have used the best available commercial and scientific 
information to evaluate the status of the Carolina and South Atlantic 
DPSs, but we agree with the reviewer that long-term, continuous, 
standardized studies of Atlantic sturgeon abundance are needed.
    Comment 7 (viable population sizes and sturgeon genetics): Peer 
reviewer 1 stated the minimum viable population

[[Page 5922]]

sizes of several hundreds to several thousands of individuals advanced 
in the literature are not particularly instructive with respect to 
sturgeon species based on new genetic information (Kreiger et al., 
2006). The reviewer commented that sturgeon are polyploid and the 
significance of polyploidy upon genetic diversity has just emerged. 
Most fishes are diploid with 40-50 chromosomes, a number similar to 
most vertebrates. However, all sturgeons are polyploid, having 
approximately 120 chromosomes (tetraploid, 4N), 240 chromosomes 
(octoploid, 8N) or more, including species with 12N or 16N ploidy. 
Polyploidy allows for multiple alleles (not just two as in diploid 
species) at a given gene locus, allowing for intra-individual genetic 
variation (Kreiger et al. 2006). The reviewer suggested that this might 
explain the high degree of plasticity displayed by sturgeon populations 
and the documented ability of sturgeons to repopulate from very few 
spawning adults without apparent inbreeding depression. He concluded 
that until we gain a deeper understanding of the genetics of polyploidy 
and the implications regarding sturgeon population dynamics, any 
discussion of minimum viable population size for sturgeon populations 
cannot be phrased in terms of what we know about inbreeding depression 
in diploid mammal populations. Thus, the 50/500 rule of thumb cited in 
the proposed listing rule may be an inappropriate criterion by which to 
assess viability of sturgeon populations, and we do not know how few 
polyploid sturgeons are too few to sustain a viable population.
    Response: We appreciate the peer reviewer's input on the polyploid 
nature of Atlantic sturgeon and how this genetic characteristic may 
affect our evaluation of minimum viable population sizes in our listing 
determination. We revised the relevant discussion in the text from the 
proposed listing rule to include this information. As noted by the 
reviewer, we need a deeper understanding of the genetics of polyploidy 
and the implications regarding sturgeon population dynamics. We are not 
sure how polyploidy in Atlantic sturgeon will affect their recovery, 
but even if it allows the species to repopulate from relatively fewer 
individuals without inbreeding depression, there is no assurance that 
this will occur. Other polyploid Acipenser species have required 
listing under the ESA, such as shortnose sturgeon (listed as endangered 
in 1967), Gulf sturgeon (listed as threatened in 1991), and green 
sturgeon (listed as threatened in 2006). In the case of the shortnose 
sturgeon, recovery has not been achieved even though it has been 
protected for almost 45 years. Further, the polyploid nature of 
Atlantic sturgeon may further support the need for protection under the 
ESA. Southern populations of Atlantic sturgeon exhibit high diversity 
and many low frequency (and sometimes private) haplotypes (Grunwald et 
al., 2008). Allendorf and Leary (1988) noted that in polyploid 
cutthroat trout, alleles constituting the majority of the variation in 
the species are found in only one or two local populations, but they 
often occur at high frequencies in those populations. They concluded 
preserving the genetic variation in cutthroat trout entails pre