Endangered and Threatened Wildlife and Plants; Proposed Listings for Two Distinct Population Segments of Atlantic Sturgeon (Acipenser oxyrinchus oxyrinchus) in the Southeast, 61904-61929 [2010-24461]

Agencies

• DEPARTMENT OF COMMERCE
• National Oceanic and Atmospheric Administration

[Federal Register Volume 75, Number 193 (Wednesday, October 6, 2010)]
[Proposed Rules]
[Pages 61904-61929]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2010-24461]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

50 CFR Part 224

RIN 0648-XN50
[Docket No. 090219208-9210-01]


Endangered and Threatened Wildlife and Plants; Proposed Listings 
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: Proposed rule; request for comments.

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SUMMARY: In 2007, a Status Review Team (SRT) consisting of Federal 
biologists from NMFS, U.S. Geological Survey (USGS), and U.S. Fish and 
Wildlife Service (USFWS) completed a status review report on Atlantic 
sturgeon (Acipenser oxyrinchus oxyrinchus) in the United States. We, 
NMFS, have reviewed this status review report and all other best 
available information to determine if listing Atlantic sturgeon under 
the Endangered Species Act (ESA) as either threatened or endangered is 
warranted. The SRT recommended that Atlantic sturgeon in the United 
States be divided into the following five distinct population segments 
(DPSs): Gulf of Maine; New York Bight; Chesapeake Bay; Carolina; and 
South Atlantic, and we agree with this DPS structure. After reviewing 
the available information on the Carolina and South Atlantic DPSs, the 
two DPSs located within the NMFS Southeast Region, we have determined 
that listing these two DPSs as endangered is warranted. Therefore, we 
propose to list these two DPSs as endangered under the ESA. We have 
published a separate listing determination for the DPSs within the NMFS 
Northeast Region in today's Federal Register.

DATES: Comments on this proposed rule must be received by January 4, 
2011. At least one public hearing will be held in a central location 
for each DPS; notice of the location(s) and time(s) of the hearing(s) 
will be subsequently published in the Federal Register not less than 15 
days before the hearing is held.

ADDRESSES: You may submit comments, identified by the XRIN 0648-XN50, 
by any of the following methods:
     Electronic Submissions: Submit all electronic public 
comments via the Federal eRulemaking Portal http//www.regulations.gov. 
Follow the instructions for submitting comments.
     Mail or hand-delivery: Assistant Regional Administrator 
for Protected Resources, NMFS, Southeast Regional Office, 263 13th 
Avenue South, St. Petersburg, FL 33701.
     Facsimile (fax) to: 727-824-5309.
    Instructions: All comments received are considered part of the 
public record and will generally be posted to https://www.regulations.gov. All Personal Identifying Information (i.e., name, 
address, etc.) voluntarily submitted may be publicly accessible. Do not 
submit Confidential Business Information or otherwise sensitive or 
protected information. We will accept anonymous comments (enter ``n/a'' 
in the required fields if you wish to remain anonymous). Please provide 
electronic attachments using Microsoft Word, Excel, WordPerfect, or 
Adobe PDF file formats only. This proposed rule, the list of 
references, and the status review report are also available 
electronically at the NMFS Web site at https://sero.nmfs.noaa.gov/pr/sturgeon.htm.

FOR FURTHER INFORMATION CONTACT: Kelly Shotts, NMFS, Southeast Regional 
Office (727) 824-5312 or Marta Nammack, NMFS, Office of Protected 
Resources (301) 713-1401.

SUPPLEMENTARY INFORMATION: 

Public Comments Solicited

    We intend that any final action resulting from this proposal will 
be as accurate as possible and informed by the best available 
scientific and commercial information. Therefore, we request comments 
or information from the public, other concerned governmental agencies, 
the scientific community, industry, or any other interested party 
concerning this proposed rule. We particularly seek comments 
concerning:
    (1) The abundance of Atlantic sturgeon in the various river systems 
in the Carolina and South Atlantic DPSs;
    (2) The mixing of fish from different DPSs in parts of their 
ranges, particularly in the marine environment;
    (3) Information concerning the viability of and/or threats to 
Atlantic sturgeon in the Carolina and South Atlantic DPSs; and
    (4) Efforts being made to protect Atlantic sturgeon in the Carolina 
and South Atlantic DPSs.

Public Hearings

    One public hearing will be held in a central location for each DPS. 
We will schedule the public hearings on this proposal and announce the 
dates, times, and locations of those hearings, as well as how to obtain 
reasonable accommodations for disabilities, in the Federal Register and 
local newspapers at least 15 days before the first hearing.

Background

Initiation of the Status Review

    We first identified Atlantic sturgeon as a candidate species in 
1991. On June 2, 1997, NMFS and 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 (Kahnle et al., 2005). The workshop 
revealed mixed results in regards to the status of Atlantic sturgeon 
populations, despite the coastwide fishing

[[Page 61905]]

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 SRT, consisting of four NMFS, four 
USFWS, and three 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.

Listing Species 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 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' status. 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.
    We reviewed the status review report, its cited references and peer 
review comments, and information that has become available since the 
status review report was finalized in 2007. Thus, we believe this 
proposed rule is based on the best available scientific and commercial 
information. Much of the information discussed below on Atlantic 
sturgeon biology, distribution, historical abundance and threats is 
attributable to the status review report. However, we have 
independently applied the statutory provisions of the ESA, our 
regulations regarding listing determinations, and our policy on 
identification of distinct population segments, in making the proposed 
listing determinations.

Taxonomy and Life History

    There are two subspecies of Atlantic sturgeon--the Gulf sturgeon 
(Acipenser oxyrinchus desotoi) and the Atlantic sturgeon (Acipenser 
oxyrinchus oxyrinchus). Historically, the Gulf sturgeon occurred from 
the Mississippi River east to Tampa Bay. Its present range extends from 
Lake Pontchartrain and the Pearl River system in Louisiana and 
Mississippi east to the Suwannee River in Florida. The Gulf sturgeon 
was listed as threatened under the ESA in 1991. The finding in this 
proposed rule addresses the subspecies Acipenser oxyrinchus oxyrinchus 
(referred to as Atlantic sturgeon), which is distributed along the 
eastern coast of North America. Historically, sightings have been 
reported from Hamilton Inlet, Labrador, south to the St. Johns River, 
Florida. Occurrences south of the St. Johns River, Florida, and in 
Labrador may have always been rare.
    Atlantic sturgeon is a long-lived, late-maturing, estuarine-
dependent, anadromous species. Atlantic sturgeon may live up to 60 
years, reach lengths up to 14 feet (ft; 4.27 meters (m)), and weigh 
over 800 pounds (lbs; 363 kilograms (kg)). They are distinguished by 
armor-like plates and a long protruding snout that is ventrally 
located, with four barbels crossing in front. Sturgeon are omnivorous 
benthic (bottom) feeders and filter quantities of mud along with their 
food. Adult sturgeon diets include mollusks, gastropods, amphipods, 
isopods, and fish. Juvenile sturgeon feed on aquatic insects and other 
invertebrates (ASSRT, 2007).
    Vital parameters of Atlantic sturgeon populations show clinal 
variation with faster growth and earlier age at maturation in more 
southern systems, though not all data sets conform to this

[[Page 61906]]

trend. Atlantic sturgeon mature between the ages of 5 and 19 years in 
South Carolina (Smith et al., 1982), between 11 and 21 years in the 
Hudson River (Young et al., 1988), and between 22 and 34 years in the 
St. Lawrence River (Scott and Crossman, 1973). Atlantic sturgeon likely 
do not spawn every year. Multiple studies have shown that spawning 
intervals range from 1 to 5 years for males (Smith, 1985; Collins et 
al., 2000; Caron et al., 2002) and 2 to 5 years for females (Vladykov 
and Greeley, 1963; Van Eenennaam et al., 1996; Stevenson and Secor, 
1999). Fecundity of Atlantic sturgeon has been correlated with age and 
body size, with egg production ranging from 400,000 to 8 million eggs 
per year (Smith et al., 1982; Van Eenennaam and Doroshov, 1998; 
Dadswell, 2006). The average age at which 50 percent of maximum 
lifetime egg production is achieved is estimated to be 29 years, 
approximately 3 to 10 times longer than for other bony fish species 
examined (Boreman, 1997).
    Spawning adults migrate upriver in the spring, which occurs during 
February and March in southern systems, April and May in mid-Atlantic 
systems, and May and July in Canadian systems (Murawski and Pacheco, 
1977; Smith, 1985; Bain, 1997; Smith and Clugston, 1997; Caron et al., 
2002). In some southern rivers, a fall spawning migration may also 
occur (Rogers and Weber, 1995; Weber and Jennings, 1996; Moser et al., 
1998). Spawning is believed to occur in flowing water between the salt 
front and fall line of large rivers, where optimal flows are 18 to 30 
inches (in) per second (46 to 76 centimeters (cm) per second) and 
depths are 36 to 89 ft (11 to 27 m) (Borodin, 1925; Leland, 1968; Scott 
and Crossman, 1973; Crance, 1987; Bain et al., 2000). The fall line is 
the boundary between an upland region of continental bedrock and an 
alluvial coastal plain, sometimes characterized by waterfalls or 
rapids. Sturgeon eggs are highly adhesive and are deposited on the 
bottom substrate, usually on hard surfaces (e.g., cobble) (Gilbert, 
1989; Smith and Clugston, 1997). Hatching occurs approximately 94 to 
140 hours after egg deposition at corresponding temperatures of 68.0 to 
64.4 degrees Fahrenheit (20 to 18 degrees Celsius). The newly emerged 
larvae assume a demersal existence (Smith et al., 1980). The yolksac 
larval stage is completed in about 8 to 12 days, during which time the 
larvae move downstream to rearing grounds (Kynard and Horgan, 2002). 
During the first half of their migration downstream, movement is 
limited to night. During the day, larvae use benthic structure (e.g., 
gravel matrix) as refugia (Kynard and Horgan, 2002). During the latter 
half of migration, when larvae are more fully developed, movement to 
rearing grounds occurs both day and night. Juvenile sturgeon continue 
to move further downstream into brackish waters and eventually become 
residents in estuarine waters for months to years.
    Recovery of depleted populations is an inherently slow process for 
a late-maturing species such as Atlantic sturgeon. Their late age at 
maturity provides more opportunities for individuals to be removed from 
the population before reproducing. However, a long life-span also 
allows multiple opportunities to contribute to future generations 
provided the appropriate spawning habitat and conditions are available.

Distribution and Abundance

    Historically, Atlantic sturgeon were present in approximately 38 
rivers throughout their range, of which 35 rivers have been confirmed 
to have had a historical spawning population. More recently, presence 
has been documented in 36 rivers with spawning taking place in at least 
18 rivers. Spawning has been confirmed in the St. Lawrence, Annapolis, 
St. John, Kennebec, Hudson, Delaware, James, Roanoke, Tar-Pamlico, Cape 
Fear, Waccamaw, Great Pee Dee, Combahee, Edisto, Savannah, Ogeechee, 
Altamaha, and Satilla rivers. Rivers with possible, but unconfirmed, 
spawning populations include the St. Croix, Penobscot, Androscoggin, 
Sheepscot, York, Neuse, Santee and Cooper Rivers; spawning may occur in 
the Santee and/or the Cooper Rivers, but it may not result in 
successful recruitment.
    Historical records from the 1700s and 1800s document large numbers 
of sturgeon in many rivers along the Atlantic Coast. Atlantic sturgeon 
underwent significant range-wide declines from historical abundance 
levels due to overfishing in the late 1800s, as discussed more fully 
below. Sturgeon stocks were further impacted through environmental 
degradation, especially due to habitat loss and reduced water quality 
from the construction of dams in the early to mid-1900s. The species 
persisted in many rivers, though at greatly reduced levels (1 to 5 
percent of their earliest recorded numbers), and commercial fisheries 
were active in many rivers during all or some of the years 1962 to 
1997. Many of these contemporary fisheries resulted in continued 
overfishing, which prompted ASMFC to impose the Atlantic sturgeon 
fishing moratorium in 1998 and NMFS to close the EEZ to Atlantic 
sturgeon retention in 1999.
    Abundance estimates of Atlantic sturgeon are currently only 
available for the Hudson (NY) and Altamaha (GA) rivers, where adult 
spawning populations are estimated to be approximately 870 and 343 fish 
per year, respectively (Kahnle et al., 2007; Schueller and Peterson, 
2006). Surveys from other rivers in the species' U.S. range are more 
qualitative, primarily focusing on documentation of multiple year 
classes and reproduction, as well as the presence of very large adults 
and gravid females, in the river systems. In the Southeast Region, 
spawning has been confirmed in 11 rivers (Roanoke, Tar-Pamlico, Cape 
Fear, Waccamaw, Great Pee Dee, Combahee, Edisto, Savannah, Ogeechee, 
Altamaha, and Satilla rivers), with possible spawning occurring in 3 
additional river (the Neuse, Santee and Cooper Rivers). Based on a 
comprehensive review of the available data, the literature, and 
information provided by local, state, and Federal fishery management 
personnel, the Altamaha River is believed to have the largest 
population in the Southeast (ASSRT, 2007). The larger size of this 
population relative to the other river populations in the Southeast is 
likely due to the absence of dams, the lack of heavy development in the 
watershed, and relatively good water quality, as Atlantic sturgeon 
populations in the other rivers in the Southeast have been affected by 
one or more of these factors. Trammel net surveys, as well as 
independent monitoring of incidental take in the American shad fishery, 
suggest that the Altamaha population is neither increasing nor 
decreasing. Though abundance estimates are not available for the other 
river populations, because the Altamaha spawning population is the 
largest, we believe a conservative estimate of the other spawning 
populations in the Southeast Region is no more than 300 adults spawning 
per year.
    Historically, Atlantic sturgeon were abundant in most North 
Carolina coastal rivers and estuaries, with the largest fisheries 
occurring in the Roanoke River/Albemarle Sound system and in the Cape 
Fear River (Kahnle et al., 1998). Historical landings records from the 
late 1800s indicated that Atlantic sturgeon were very abundant within 
Albemarle Sound (approximately 135,600 lbs or 61,500 kg landed per 
year). Abundance estimates derived from these historical landings 
records indicated that between 7,200 and 10,500 adult females were 
present within North Carolina prior to 1890 (Armstrong and

[[Page 61907]]

Hightower, 2002; Secor, 2002). The North Carolina Division of Marine 
Fisheries (NCDMF) has conducted the Albemarle Sound Independent Gill 
Net Survey (IGNS), initially designed to target striped bass, since 
1990. During that time, 842 young-of-the-year (YOY) and subadult 
sturgeon have been captured. Incidental take of Atlantic sturgeon in 
the IGNS, as well as multiple observations of YOY from the Albemarle 
Sound and Roanoke River, provide evidence that spawning continues, and 
catch records indicate that this population seemed to be increasing 
until 2000, when recruitment began to decline. Catch records and 
observations from other river systems in North Carolina exist (e.g., 
Hoff, 1980, Oakley, 2003, in the Tar and Neuse rivers; Moser et al., 
1998, and Williams and Lankford, 2003, in the Cape Fear River) and 
provide evidence for spawning, but based on the relatively low numbers 
of fish caught, it is difficult to determine whether the populations in 
those systems are declining, rebounding, or remaining static. Also, 
large survey captures during a single year are difficult to interpret. 
For instance, abundance of Atlantic sturgeon below Lock and Dam 
1 in the Cape Fear River seemed to have increased dramatically 
during the 1990-1997 surveys (Moser et al., 1998) as the catch per unit 
effort (CPUE) of Atlantic sturgeon was up to eight times greater during 
1997 than in the earlier survey years. Since 1997, Atlantic sturgeon 
CPUE doubled between the years of 1997 and 2003 (Williams and Lankford, 
2003). However, it is unknown whether this is an actual population 
increase reflecting the effects of North Carolina's ban on Atlantic 
sturgeon fishing that began in 1991, or whether the results were skewed 
by one outlier year. There was a large increase observed in 2002, 
though the estimates were similar among all other years of the 1997 to 
2003 study.
    Atlantic sturgeon were likely present in many South Carolina river/
estuary systems historically, but it is not known where spawning 
occurred. Secor (2002) estimated that 8,000 spawning females were 
likely present prior to 1890, based on U.S. Fish Commission landing 
records. Since the 1800s, however, populations have declined 
dramatically (Collins and Smith, 1997). Recorded landings of Atlantic 
sturgeon in South Carolina peaked at 481,050 lbs (218,200 kg) in 1897, 
but 5 years later, only 93,920 lbs (42,600 kg) were reported landed 
(Smith et al., 1984). Landings remained depressed throughout the 1900s, 
with between 4,410 and 99,210 lbs (2,000 and 45,000 kg) of Atlantic 
sturgeon reported annually between 1958 and 1982 (Smith et al., 1984). 
During the last two decades, Atlantic sturgeon have been observed in 
most South Carolina coastal rivers, although it is not known if all 
rivers support a spawning population (Collins and Smith, 1997). Recent 
sampling for shortnose sturgeon (Acipenser brevirostrum) conducted in 
Winyah Bay captured two subadult Atlantic sturgeon in 2004. Captures of 
age-1 juveniles from the Waccamaw River during the early 1980s suggest 
that a reproducing population of Atlantic sturgeon may persist in that 
river, although the fish could have been from the nearby Great Pee Dee 
River (Collins and Smith, 1997). Until recently, there was no evidence 
that Atlantic sturgeon spawned in the Great Pee Dee River, although 
subadults were frequently captured and large adults were often observed 
by fishers. However, a fishery survey conducted by Progress Energy 
Carolinas Incorporated captured a running ripe male in October 2003 and 
observed other large sturgeon, perhaps revealing a fall spawning run 
(ASSRT, 2007). There are no data available regarding the presence of 
YOY or spawning adult Atlantic sturgeon in the Sampit River, although 
it did historically support a population and is thought to serve as a 
nursery ground for local stocks (ASMFC, 2009).
    The Santee-Cooper system had some of the highest historical 
landings of Atlantic sturgeon in the Southeast. Data from the U.S. Fish 
Commission shows that greater than 220,460 lbs (100,000 kg) of Atlantic 
sturgeon were landed in 1890 (Secor, 2002). The capture of 151 
subadults, including age-1 juveniles, in the Santee River in 1997 
suggests that an Atlantic sturgeon population still exists in this 
river (Collins and Smith, 1997). The status review report documents 
that three adult Atlantic sturgeon carcasses were found above the 
Wilson and Pinopolis dams in Lake Moultrie (a Santee-Cooper reservoir) 
during the 1990s, and also states that there is little information 
regarding a land-locked population existing above the dams. There is no 
effective fish passage for sturgeon on the Santee and Cooper Rivers, 
and the lowest dams on these rivers are well below the fall line, thus 
limiting the amount of freshwater spawning and developmental habitat 
for fish below the dams. In 2007, an Atlantic sturgeon entered the lock 
at the St. Stephens dam; it was physically removed and translocated 
downstream into the Santee River (A. Crosby, SCDNR, pers. comm.) In 
2004, 15 subadult Atlantic sturgeon were captured in shortnose sturgeon 
surveys in the Santee River estuary. The previous winter, four juvenile 
(YOY and subadults) Atlantic sturgeon were captured from the Santee 
(one fish) and Cooper (three fish) rivers. These data support previous 
hypotheses that a fall spawning run occurs within this system, similar 
to that observed in other southern river systems. However, the status 
review report notes that SCDNR biologists have some doubt whether 
smaller sturgeon from the Santee-Cooper are resident YOY, as flood 
waters from the Pee-Dee or Waccamaw Rivers could have transported these 
YOY to the Santee-Cooper system via Winyah Bay and the Intracoastal 
Waterway (McCord, 2004). Resident YOY could, however, be evidence of a 
spawning population above the dams, as is the case with shortnose 
sturgeon (S. Bolden, pers. comm.).
    From 1994 to 2001, over 3,000 juveniles have been collected in the 
Ashepoo-Combahee-Edisto Rivers (ACE) Basin, including 1,331 YOY 
sturgeon (Collins and Smith, 1997; ASSRT, 2007). Sampling for adults 
began in 1997, with two adult sturgeon captured in the first year of 
the survey, including one gravid female captured in the Edisto River 
and one running ripe male captured in the Combahee River. The running 
ripe male in the Combahee River was recaptured one week later in the 
Edisto River, which suggests that the three rivers that make up the ACE 
Basin may support a single population that spawns in at least two of 
the rivers. In 1998, an additional 39 spawning adults were captured 
(ASSRT, 2007). These captures show that a current spawning population 
exists in the ACE Basin, as both YOY and spawning adults are regularly 
captured.
    The Ashley River, along with the Cooper River, drains into 
Charleston Bay; only shortnose sturgeon have been sampled in these 
rivers. While the Ashley River historically supported an Atlantic 
sturgeon spawning population, it is unknown whether the population 
still exists. There has been little or no scientific sampling for 
Atlantic sturgeon in the Broad/Coosawatchie River. One fish of unknown 
size was reported from a small directed fishery during 1981 to 1982 
(Smith and Dingley, 1984).
    Prior to the collapse of the fishery in the late 1800s, the 
sturgeon fishery was the third largest fishery in Georgia. Secor (2002) 
estimated from U.S. Fish Commission landing reports that approximately 
11,000 spawning females were likely present prior to 1890. The sturgeon 
fishery was mainly centered on the Altamaha River, and in more recent 
years, peak landings were recorded in

[[Page 61908]]

1982 (13,000 lbs, 5,900 kg). Based on juvenile presence and abundance, 
the Altamaha River currently supports one of the healthier Atlantic 
sturgeon populations in the southeast (ASSRT, 2007). Atlantic sturgeon 
are also present in the Ogeechee River; however, the absence of age-1 
fish during some years and the unbalanced age structure suggests that 
the population is highly stressed (Rogers and Weber, 1995). Sampling 
results indicate that the Atlantic sturgeon population in the Satilla 
River is also highly stressed (Rogers and Weber, 1995). Only four 
spawning adults or YOY, which were used for genetic analysis (Ong et 
al., 1996), have been collected from this river since 1995. In Georgia, 
Atlantic sturgeon are believed to spawn in the Savannah, Ogeechee, 
Altamaha, and Satilla rivers. The Savannah River supports a reproducing 
population of Atlantic sturgeon (Collins and Smith, 1997). According to 
NOAA's National Ocean Service, 70 Atlantic sturgeon have been captured 
since 1999 (ASSRT, 2007). Twenty-two of these fish have been YOY. A 
running ripe male was captured at the base of the dam at Augusta during 
the late summer of 1997, which supports the hypothesis that spawning 
occurs there in the fall.
    Reproducing Atlantic sturgeon populations are no longer believed to 
exist south of the Satilla River in Georgia. Recent sampling of the St. 
Marys River failed to locate any sturgeon, which suggests that the 
spawning population may be extirpated (Rogers et al., 1994; NMFS 2009). 
In January 2010, 12 sturgeon, believed to be Atlantics, were captured 
at the mouth of the St. Marys during relocation trawling associated 
with a dredging project (J. Wilcox, Florida Fish and Wildlife 
Conservation Commission, Pers. Comm.), the first capture of Atlantics 
in the St. Marys in decades. However, because they were not YOY or 
adults captured upstream, these trawl-captured sturgeon do not provide 
new evidence of a spawning population in the St. Marys. There have been 
reports of Atlantic sturgeon tagged in the Edisto River (South 
Carolina) being recaptured in the St. Johns River, indicating this 
river may serve as a nursery ground; however, there are no data to 
support the existence of a current spawning population (i.e., YOY or 
running ripe adults) in the St. Johns (Rogers and Weber, 1995; Kahnle 
et al., 1998).

Identification of Distinct Population Segments

    The ESA's definition of ``species'' includes ``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 high degree of reproductive isolation of Atlantic sturgeon (i.e., 
homing to their natal rivers for spawning) (ASSRT, 2007; Wirgin et al., 
2000; King et al., 2001; Waldman et al., 2002), as well as the 
ecological uniqueness of those riverine spawning habitats, the genetic 
diversity amongst subpopulations, and the differences in life history 
characteristics, provide evidence that discrete reproducing populations 
of Atlantic sturgeon exist, which led the Services to evaluate 
application of the DPS policy in its 2007 status review. To determine 
whether any populations qualify as DPSs, we evaluated populations 
pursuant to the joint DPS policy, and considered: (1) The discreteness 
of any Atlantic sturgeon population segment in relation to the 
remainder of the subspecies to which it belongs; and (2) the 
significance of any Atlantic sturgeon population segment to the 
remainder of the subspecies to which it belongs.

Discreteness

    The joint DPS policy states that a population of a vertebrate 
species may be considered discrete if it satisfies either one of the 
following conditions: (1) It is markedly separated from other 
populations of the same taxon as a consequence of physical, 
physiological, ecological, or behavioral factors (quantitative measures 
of genetic or morphological discontinuity may provide evidence of this 
separation) or (2) it is delimited by international governmental 
boundaries within which differences in control of exploitation, 
management of habitat, conservation status, or regulatory mechanisms 
exist that are significant in light of Section 4(a)(1)(D) of the ESA.
    Atlantic sturgeon throughout their range exhibit ecological 
separation during spawning that has resulted in multiple genetically 
distinct interbreeding population segments. Tagging studies and genetic 
analyses provide the evidence of this ecological separation (Wirgin et 
al., 2000; King et al., 2001; Waldman et al., 2002; ASSRT, 2007; 
Grunwald et al., 2008). As previously discussed, though adult and 
subadult Atlantic sturgeon originating from different rivers mix in the 
marine environment (Stein et al., 2004a), the vast majority of Atlantic 
sturgeon return to their natal rivers to spawn, with some studies 
showing one or two individuals per generation spawning outside their 
natal river system (Wirgin et al., 2000; King et al., 2001; Waldman et 
al., 2002). In addition, spawning in the various river systems occurs 
at different times, with spawning occurring earliest in southern 
systems and occurring as much as 5 months later in the northernmost 
river systems (Murawski and Pacheco, 1977; Smith, 1985; Rogers and 
Weber, 1995; Weber and Jennings, 1996; Bain, 1997; Smith and Clugston, 
1997; Moser et al., 1998; Caron et al., 2002). Therefore, the 
ecological separation of the interbreeding units of Atlantic sturgeon 
results primarily from spatial separation (i.e., very few fish spawning 
outside their natal river systems), as well as temporal separation 
(spawning populations becoming active at different times along a 
continuum from north to south).
    Genetic analyses of mitochondrial DNA (mtDNA), which is maternally 
inherited, and nuclear DNA (nDNA), which reflects the genetics of both 
parents, provides evidence of the separation amongst Atlantic sturgeon 
populations in different rivers (Bowen and Avise, 1990; Ong et al., 
1996; Waldman et al., 1996a; Waldman et al., 1996b; Waldman and Wirgin, 
1998; Waldman et al., 2002; King et al., 2001; Wirgin et al., 2002; 
Wirgin et al., 2005; Wirgin and King, 2006; Grunwald et al., 2008). 
Overall, these studies consistently found Atlantic sturgeon to be 
genetically diverse, and offered that between seven and ten Atlantic 
sturgeon population groupings can be statistically differentiated 
range-wide (King et al., 2001; Waldman et al., 2002; Wirgin et al., 
2002; Wirgin et al., 2005; ASSRT, 2007 (Tables 4 and 5); Grunwald et 
al., 2008).
    Given a number of key differences amongst the studies (e.g., the 
analytical and/or statistical methods used, the number of rivers 
sampled, and whether samples from subadults were included), it is not 
unexpected that each reached a different conclusion as to the number of 
Atlantic sturgeon population groupings. Wirgin and King (2006) refined 
the genetic analyses for Atlantic sturgeon to address such differences 
in prior studies. Most notably, they increased sample sizes from 
multiple rivers and limited the samples analyzed to those collected 
from YOY and mature adults (greater than 130 cm total length) to ensure 
that the fish originated from the river in which it was sampled. The 
results of the refined analysis by Wirgin and King (2006) are presented 
in the status review report (ASSRT, 2007; e.g., Table 6 and Figure 17); 
both the mtDNA haplotype and nDNA allelic frequencies analyzed by 
Wirgin and King (2006) indicated that Atlantic sturgeon river 
populations are genetically differentiated. The results of the mtDNA 
analysis used for the status review

[[Page 61909]]

report were also subsequently published by Grunwald et al. (2008). In 
comparison to the mtDNA analyses of the status review report, Grunwald 
et al. (2008) used additional samples, some from fish in the size range 
(less than 130 cm) excluded by Wirgin and King because they were 
smaller than those considered to be mature adults. Nevertheless, the 
results were qualitatively the same and demonstrated that each of the 
12 sampled Atlantic sturgeon populations could be genetically 
differentiated (Grunwald et al., 2008).
    Genetic distances and statistical analyses (bootstrap values and 
assignment test values) were used to investigate significant 
relationships among, and differences between, Atlantic sturgeon river 
populations (ASSRT, 2007; Table 6 and Figures 16-18). Overall, the 
genetic markers used in this analysis resulted in an average accuracy 
of only 88 percent for determining a sturgeon's natal river origin, but 
an average accuracy of 94 percent for correctly classifying it to one 
of five groups of populations (Kennebec River, Hudson River, James 
River, Albemarle Sound, and Savannah/Ogeechee/Altamaha Rivers) when 
using microsatellite data collected only from YOY and adults (ASSRT, 
2007; Table 6). A phylogenetic tree (a neighbor joining tree) was 
produced from only YOY and adult samples (to reduce the likelihood of 
including strays from other populations) using the microsatellite 
analysis (ASSRT, 2007; Figure 17). Bootstrap values (which measure how 
consistently the data support the tree structure) for this tree were 
high (equal to or greater than 87 percent, and all but one over 90 
percent) (ASSRT, 2007). Regarding sturgeon from southeast rivers, this 
analysis resulted in a range of 60 to 92 percent accuracy in 
determining a sturgeon's natal river origin, but 92 and 96 percent 
accuracy in correctly classifying a sturgeon from four sampled river 
populations (the Albemarle Sound, Savannah, Ogeechee, and Altamaha 
River populations) to two groupings of river populations (Albemarle 
Sound and Savannah/Ogeechee/Altamaha Rivers). These two groupings 
exhibited clear separation from northern populations and from each 
other.
    Genetic samples for YOY and spawning adults were not available for 
river populations originating between the Albemarle Sound and the other 
three rivers. However, nDNA from an expanded dataset that included 
juvenile Atlantic sturgeon was used to produce a neighbor-joining tree 
with bootstrap values (ASSRT, 2007; Figure 18). This dataset included 
additional samples from the Santee-Cooper, Waccamaw, and Edisto 
populations in the Southeast. Atlantic sturgeon river populations also 
grouped into five population segments in this analysis. Atlantic 
sturgeon from the Santee-Cooper system grouped with the Albemarle Sound 
population, while the other two river populations grouped with the 
Savannah/Ogeechee/Altamaha River population segment. With the exception 
of the Waccamaw River population, all river populations sampled within 
each population segment along the entire East Coast were geographically 
adjacent. The Waccamaw River population grouped with the Edisto/
Savannah/Ogeechee/Altamaha River population segment, even though it is 
geographically located between Albemarle Sound and the Santee and 
Cooper Rivers. However, we attributed this to the small sample size (21 
fish) from the Waccamaw River. From the seven Southeast river 
populations included in the analysis, we determined that river 
populations from the ACE Basin southward grouped together and that 
river populations between the Santee-Cooper system and Albemarle Sound 
(Roanoke River) grouped together.
    The higher accuracy in identifying Atlantic sturgeon to one of two 
population groupings (Albemarle Sound/Santee-Cooper Rivers and 
Ogeechee/Savannah/Altamaha/Edisto Rivers) compared to their natal 
rivers supports the fact that these multiple-river population segments 
are discrete from each other.
    We have considered the information on Atlantic sturgeon population 
structuring provided in the status review report and Grunwald et al. 
(2008). The nDNA analyses described in the status review report provide 
additional genetics information, and include chord distances and 
bootstrap values to support the findings for population structuring of 
Atlantic sturgeon within the United States. Therefore, based on genetic 
differences observed between certain river populations and the 
assumption that adjacent river populations are more likely to breed 
with one another than river populations from rivers that are not 
adjacent to each other, five discrete Atlantic sturgeon population 
segments in the United States meet the DPS Policy's Discreteness 
criterion, with two located in the Southeast: (1) The ``Carolina'' 
population segment, which includes Atlantic sturgeon originating from 
the Roanoke, Tar/Pamlico, Cape Fear, Waccamaw, Pee Dee, and Santee-
Cooper Rivers, and (2) the ``South Atlantic'' population segment, which 
includes Atlantic sturgeon originating from the ACE Basin (Ashepoo, 
Combahee, and Edisto rivers), Savannah, Ogeechee, Altamaha, and Satilla 
Rivers.

Significance

    When the discreteness criterion is met for a potential DPS, as it 
is for the Carolina and South Atlantic population segments in the 
Southeast identified above, the second element that must be considered 
under the DPS policy is significance of each DPS to the taxon as a 
whole. The DPS policy cites examples of potential considerations 
indicating significance, including: (1) Persistence of the discrete 
population segment in an ecological setting unusual or unique for the 
taxon; (2) evidence that loss of the discrete population segment would 
result in a significant gap in the range of the taxon; (3) evidence 
that the DPS represents the only surviving natural occurrence of a 
taxon that may be more abundant elsewhere as an introduced population 
outside its historic range; or, (4) evidence that the discrete 
population segment differs markedly from other populations of the 
species in its genetic characteristics.
    We believe that the Carolina and South Atlantic population segments 
persist in ecological settings unique for the taxon. This is evidenced 
by the fact that spawning habitat of each population grouping is found 
in separate and distinct ecoregions that were identified by The Nature 
Conservancy (TNC) based on the habitat, climate, geology, and 
physiographic differences for both terrestrial and marine ecosystems 
throughout the range of the Atlantic sturgeon along the Atlantic coast 
(Figure 1). TNC descriptions do not include detailed information on the 
chemical properties of the rivers within each ecoregion, but include an 
analysis of bedrock and surficial geology type because it relates to 
water chemistry, hydrologic regime, and substrate. It is well 
established that waters have different chemical properties (i.e., 
identities) depending on the geology of where the waters originate.
    Riverine spawning habitat of the Carolina population segment occurs 
within the Mid-Atlantic Coastal Plain ecoregion, which is described as 
consisting of bottomland hardwood forests, swamps, and some of the 
world's most active coastal dunes, sounds, and estuaries. Natural 
fires, floods, and storms are so dominant in this region that the 
landscape changes very quickly. Rivers routinely change their courses 
and emerge from their banks. The TNC lists the most

[[Page 61910]]

significant threats (sources of biological and ecological stress) in 
the region as: global climate change and rising sea-level; altered 
surface hydrology and landform alteration (e.g., flood-control and 
hydroelectric dams, inter-basin transfers of water, drainage ditches, 
breached levees, artificial levees, dredged inlets and river channels, 
beach renourishment, and spoil deposition banks and piles); a 
regionally receding water table, probably resulting from both over-use 
and inadequate recharge; fire suppression; land fragmentation, mainly 
by highway development; land-use conversion (e.g., from forests to 
timber plantations, farms, golf courses, housing developments, and 
resorts); the invasion of exotic plants and animals; air and water 
pollution, mainly from agricultural activities including concentrated 
animal feed operations; and over-harvesting and poaching of species. 
Many of the Carolina population segment's spawning rivers, located in 
the Mid-Coastal Plain, originate in areas of marl. Waters draining 
calcareous, impervious surface materials such as marl are likely to be 
alkaline, dominated by surface run-off, have little groundwater 
connection, and be seasonally ephemeral.
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    The riverine spawning habitat of the South Atlantic population 
segment occurs within the South Atlantic Coastal Plain ecoregion. TNC 
describes the South Atlantic Coastal Plain ecoregion as fall-line 
sandhills to rolling longleaf pine uplands to wet pine flatwoods; from 
small streams to large river systems to rich estuaries; from isolated 
depression wetlands to Carolina bays to the Okefenokee Swamp. Other 
ecological systems in the ecoregion include maritime forests on barrier 
islands, pitcher plant seepage bogs and Altamaha grit (sandstone) 
outcrops. The primary threats to biological diversity in the South 
Atlantic Coastal Plain listed

[[Page 61912]]

by TNC are intensive silvicultural practices, including conversion of 
natural forests to highly managed pine monocultures and the clear-
cutting of bottomland hardwood forests. Changes in water quality and 
quantity, caused by hydrologic alterations (impoundments, groundwater 
withdrawal, and ditching), and point and nonpoint pollution, are 
threatening the aquatic systems. Development is a growing threat, 
especially in coastal areas. Agricultural conversion, fire regime 
alteration, and the introduction of nonnative species are additional 
threats to the ecoregion's diversity. The South Atlantic DPS' spawning 
rivers, located in the South Atlantic Coastal Plain, are primarily of 
two types: brownwater (with headwaters north of the Fall Line, silt-
laden) and blackwater (with headwaters in the coastal plain, stained by 
tannic acids).
    Therefore, the ecoregion delineations support that the physical and 
chemical properties of the Atlantic sturgeon spawning rivers utilized 
by the Carolina and South Atlantic DPSs are unique to each population 
segment. Since reproductive isolation accounts for the discreteness of 
each population segment, the Carolina and South Atlantic population 
segments of Atlantic sturgeon are ``significant'' as defined in the DPS 
policy given that the spawning rivers for each population segment occur 
in a unique ecological setting.
    The loss of either the Carolina or the South Atlantic population 
segments of Atlantic sturgeon would create a significant gap in the 
range of the taxon. The loss of the Carolina population segment would 
result in a 475-mile (764-kilometer (km)) gap between the northern 
population segments and the South Atlantic population segment. The loss 
of the South Atlantic population segment would truncate the southern 
range of Atlantic sturgeon by greater than 150 miles (241 km). Though 
Atlantic sturgeon travel great distances in the marine environment and 
may use multiple river systems for foraging and nursery habitat, the 
range occupied by the Carolina and South Atlantic population segments 
would likely not be recolonized by a new, viable spawning population if 
either population segment was lost. Based on genetic analyses showing 
that fewer than two individuals per generation spawn outside their 
natal rivers (Secor and Waldman, 1999), we do not expect Atlantic 
sturgeon that originate from other population segments to re-colonize 
extirpated systems and establish new spawning populations, except 
perhaps over a long time frame (i.e., many Atlantic sturgeon 
generations). Therefore, the loss of either the Carolina or South 
Atlantic population segments would result in a significant gap in the 
range of Atlantic sturgeon over a long time frame, and negatively 
impact the species as a whole because the loss of either population 
segment would constitute an important loss of genetic diversity for the 
Atlantic sturgeon.
    The information presented above describes: (1) Persistence of the 
Carolina and South Atlantic population segments in ecological settings 
that are unique for the Atlantic sturgeon as a whole; and (2) evidence 
that loss of either population segment would result in a significant 
gap in the range of the taxon. Based on this information, we concur 
with the SRT's conclusion that the Carolina and South Atlantic 
population segments meet the discreteness and significance criteria 
outlined in the DPS policy. We hereafter refer to these DPSs as the 
Carolina and South Atlantic DPSs. Figure 2 shows the riverine and U.S. 
marine ranges of the Carolina and South Atlantic DPSs.
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[[Page 61913]]

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Conservation Status

    We will now consider the conservation status of the two DPSs in the 
Southeast Region's jurisdiction, the Carolina and South Atlantic DPSs, 
in relation to the ESA's standards for listing. We will determine 
whether each DPS meets the definition of ``endangered'' or 
``threatened'' as defined in section 3 of the ESA, and whether that 
status is a result of one or a combination of the factors listed under 
section 4(a)(1) of the ESA. An endangered species is ``any species 
which is in danger of extinction throughout all or a significant 
portion of its range'' and a threatened species is one ``which is 
likely to become an endangered species within the foreseeable future 
throughout all or a significant portion of its range.''

[[Page 61914]]

    The abundance of Atlantic sturgeon has decreased dramatically 
within the last 150 years. A major fishery for Atlantic sturgeon 
developed in 1870 when a caviar market was established (Smith and 
Clugston, 1997). Record landings in the U.S. were reported in 1890, 
with over 7,385,000 lbs (3,350,000 kg) of Atlantic sturgeon landed from 
coastal rivers along the entire Atlantic Coast (Smith and Clugston, 
1997; Secor and Waldman, 1999). Ten years after peak landings, the 
fishery collapsed in 1901, when less than 10 percent (650,365 lbs, 
295,000 kg) of the U.S. 1890 peak landings were reported. The landings 
continued to decline coastwide, reaching about 5 percent of the peak in 
1920. During the 1950s, the remaining U.S. fishery switched to 
targeting sturgeon for flesh, rather than caviar, and coastwide 
landings remained between 1 and 5 percent of the 1890 peak levels until 
the Atlantic sturgeon fishery was closed by ASMFC in 1998.
    The Carolina DPS includes all Atlantic sturgeon that spawn in the 
watersheds from the Roanoke River, Virginia, southward along the 
southern Virginia, North Carolina, and South Carolina coastal areas to 
the Cooper River. The marine range of Atlantic sturgeon from the 
Carolina DPS extends from the Bay of Fundy, Canada, to the Saint Johns 
River, Florida. While Atlantic sturgeon exhibit a high degree of 
spawning fidelity to their natal rivers, multiple riverine, estuarine, 
and marine habitats may serve various life (e.g., nursery, foraging, 
and migration) functions. Rivers known to have current spawning 
populations within the range of this DPS include the Roanoke, Tar-
Pamlico, Cape Fear, Waccamaw, and Pee Dee Rivers. There may also be 
spawning populations in the Neuse, Santee and Cooper Rivers, though it 
is uncertain at this time. Historically, both the Sampit and Ashley 
Rivers were documented to have spawning populations at one time. 
However, the spawning population in the Sampit River is believed to be 
extirpated and the current status of the spawning population in the 
Ashley River is unknown. Both rivers may be used as nursery habitat by 
young Atlantic sturgeon originating from other spawning populations. 
This represents our current knowledge of the river systems utilized by 
the Carolina DPS for specific life functions, such as spawning, nursery 
habitat, and foraging. However, fish from the Carolina DPS likely use 
other river systems than those listed here for their specific life 
functions. The Carolina DPS also includes Atlantic sturgeon held in 
captivity (e.g., aquaria, hatcheries, and scientific institutions) and 
which are identified as fish belonging to the Carolina DPS based on 
genetics analyses, previously applied tags, previously applied marks, 
or documentation to verify that the fish originated from (hatched in) a 
river within the range of the Carolina DPS, or is the progeny of any 
fish that originated from a river within the range of the Carolina DPS. 
NMFS has no records of Atlantic sturgeon from the Carolina DPS being 
held in captivity.
    Historical landings data indicate that between 7,000 and 10,500 
adult female Atlantic sturgeon were present in North Carolina prior to 
1890 (Armstrong and Hightower, 2002; Secor, 2002). Secor (2002) 
estimates that 8,000 adult females were present in South Carolina 
during that same timeframe. Prior reductions from the commercial 
fishery and ongoing threats have drastically reduced the numbers of 
Atlantic sturgeon within the Carolina DPS. Currently, the Atlantic 
sturgeon spawning population in at least one river system within the 
Carolina DPS has been extirpated, with a potential extirpation in an 
additional system. The abundance of the remaining river populations 
within the DPS, each estimated to have fewer than 300 spawning adults, 
is estimated to be less than 3 percent of what it was historically 
(ASSRT, 2007). Though directed fishing and possession of Atlantic 
sturgeon is no longer legal, the Carolina DPS continues to face threats 
such as habitat alteration and bycatch. The presence of dams has 
resulted in the loss of over 60 percent of the historical sturgeon 
habitat on the Cape Fear River and in the Santee-Cooper system. This 
has resulted in the loss of important spawning and juvenile 
developmental habitat and has reduced the quality of the remaining 
habitat by affecting water quality parameters (such as depth, 
temperature, velocity, and dissolved oxygen) that are important to 
sturgeon.
    The South Atlantic DPS includes all Atlantic sturgeon that spawn in 
the watersheds of the ACE Basin in South Carolina to the St. Johns 
River, Florida. The marine range of Atlantic sturgeon from the South 
Atlantic DPS extends from the Bay of Fundy, Canada, to the Saint Johns 
River, Florida. While Atlantic sturgeon exhibit a high degree of 
spawning fidelity to their natal rivers, multiple riverine, estuarine, 
and marine habitats may serve various life (e.g., nursery, foraging, 
and migration) functions. Rivers known to have current spawning 
populations within this DPS include the Combahee, Edisto, Savannah, 
Ogeechee, Altamaha, and Satilla Rivers. Historically, both the Broad-
Coosawatchie and St. Marys Rivers were documented to have spawning 
populations at one time; there is also evidence that spawning may have 
occurred in the St. Johns River or one of its tributaries. However, the 
spawning population in the St. Marys River, as well as any historical 
spawning population present in the St. Johns, is believed to be 
extirpated, and the status of the spawning population in the Broad-
Coosawatchie is unknown. Both the St. Marys and St. Johns Rivers are 
used as nursery habitat by young Atlantic sturgeon originating from 
other spawning populations. The use of the Broad-Coosawatchie by 
sturgeon from other spawning populations is unknown at this time. The 
presence of historical and current spawning populations in the Ashepoo 
River has not been documented; however, this river may currently be 
used for nursery habitat by young Atlantic sturgeon originating from 
other spawning populations. This represents our current knowledge of 
the river systems utilized by the South Atlantic DPS for specific life 
functions, such as spawning, nursery habitat, and foraging. However, 
fish from the South Atlantic DPS likely use other river systems than 
those listed here for their specific life functions. The South Atlantic 
DPS also includes Atlantic sturgeon held in captivity (e.g., aquaria, 
hatcheries, and scientific institutions) and which are identified as 
fish belonging to the South Atlantic DPS based on genetics analyses, 
previously applied tags, previously applied marks, or documentation to 
verify that the fish originated from (hatched in) a river within the 
range of the South Atlantic DPS, or is the progeny of any fish that 
originated from a river within the range of the South Atlantic DPS. Ten 
Atlantic sturgeon taken from the Altamaha River are currently being 
held at the Bears Bluff National Fish Hatchery in Warm Springs, 
Georgia, though it is not certain whether those fish were spawned in 
the Altamaha or were migrants from another river system. NMFS has no 
other records of Atlantic sturgeon from the South Atlantic DPS being 
held in captivity.
    Secor (2002) estimated that 8,000 spawning female Atlantic sturgeon 
were present in South Carolina. Historically, the population of 
spawning female Atlantic sturgeon in Georgia was estimated at 11,000 
fish per year prior to 1890 (Secor, 2002). Prior reductions from the 
commercial fishery and ongoing threats have drastically reduced

[[Page 61915]]

the numbers of Atlantic sturgeon within the South Atlantic DPS. 
Currently, the Atlantic sturgeon spawning population in one (possibly 
two) river systems within the South Atlantic DPS have been extirpated. 
The Altamaha River, with an estimated 343 spawning adults per year, is 
suspected to be less than 6 percent of its historical abundance, 
extrapolated from the 1890s commercial landings; the abundance of the 
remaining river populations within the DPS, each estimated to have 
fewer than 300 spawning adults, is estimated to be less than 1 percent 
of what it was historically (ASSRT, 2007). While the directed fishery 
that originally drastically reduced the numbers of Atlantic sturgeon 
has been closed, other impacts have contributed to their low population 
numbers, may have contributed to the extirpation of some spawning 
populations, and are likely inhibiting recovery of extant river 
populations. Historically, Atlantic sturgeon likely accessed all parts 
of the St. Johns River, as American shad were reported as far upstream 
as Lake Poinsett (reviewed in McBride, 2000). However, the construction 
of Kirkpatrick Dam (originally Rodman Dam) at river mile (RM) 95 (river 
km (RKM) 153) restricted migration to potential spawning and juvenile 
developmental habitat upstream. Approximately 63 percent of historical 
sturgeon habitat is believed to be blocked due to the dam (ASSRT, 
2007), and there is no longer a spawning population in the St. Johns 
River.
    Small numbers of individuals resulting from drastic reductions in 
populations, such as occurred with Atlantic sturgeon due to the 
commercial fishery, can remove the buffer against natural demographic 
and environmental variability provided by large populations (Berry, 
1971; Shaffer, 1981; Soule, 1980). Though the Carolina and South 
Atlantic DPSs, made up of multiple river populations of Atlantic 
sturgeon, were determined to be genetically discrete, interbreeding 
population units, the vast majority of Atlantic sturgeon return to 
their natal rivers to spawn, with fewer than two migrants per 
generation spawning outside their natal system (Wirgin et al., 2000; 
King et al., 2001; Waldman et al., 2002). Therefore, it is important to 
look at each riverine spawning population within each DPS when 
considering the effects of a small population size on the extinction 
risk for the DPS. Though there is no absolute population size above 
which populations are ``safe'' and below which they face an 
unacceptable risk of extinction (Gilpin and Soule, 1986; Soule and 
Simberloff, 1986; Ewens et al., 1987; Goodman, 1987; Simberloff, 1988; 
Thomas, 1990), some have argued that ``rules of thumb'' can and should 
be applied (Soule, 1987; Thompson, 1991). Salwasser et al. (1984) 
prescribe a minimum viable population size of at least 1,000 adults. 
Belovsky (1987) indicates that a minimum viable population in the range 
of 1,000 to 10,000 adults should be sufficient for a mid-sized 
vertebrate species. Soule (1987) suggests that minimum viable 
population sizes for vertebrate species should be in the ``low 
thousands'' or higher. Thomas (1990) offers a population size of 5,500 
as ``a useful goal,'' but suggests that where uncertainty is extreme 
``we should usually aim for population sizes from several thousand to 
ten thousand.'' In a NOAA Technical Memorandum ``Determining Minimum 
Viable Populations under the ESA,'' Thompson (1991) states the ``50/
500'' rule of thumb initially advanced by Franklin (1980) and Soule 
(1980) comes the closest of any to attaining ``magic number'' status. 
Franklin (1980) has suggested that, simply to maintain short-term 
fitness (i.e., prevent serious in-breeding and its deleterious 
effects), the minimum effective population size should be around 50. He 
further recommended that, to maintain sufficient genetic variability 
for adaptation to changing environmental conditions, the minimum 
effective population size should be around 500. Soule (1980) has 
pointed out that, above and beyond preserving short-term fitness and 
genetic adaptability, long-term evolutionary potential (at the species 
level) may well require a number of substantially larger populations. 
It is important to note that the 50/500 rule is cast in terms of 
effective population size, a concept introduced by Wright (1931). The 
effective population size refers to an ideal population of breeding 
individuals produced each generation by random union of an equal number 
of male and female gametes randomly drawn from the previous generation. 
To the extent that this ideal is violated in nature, the effective 
population size is generally smaller than the overall number of mature 
individuals in the population. It is not possible to calculate the 
effective population sizes of the riverine spawning populations in the 
Carolina or the South Atlantic DPS. However, even under ideal 
circumstances where the effective population size is equal to the 
overall numbers of adults, the spawning populations are all believed to 
be smaller than the 500 recommended by Thompson (1991) to maintain 
sufficient genetic variability for adaptation to changing environmental 
conditions, and certainly smaller than the 1,000 to 10,000 recommended 
by other authors. It is not known if certain riverine populations are 
at an abundance smaller than the minimum effective population size of 
50 that would prevent serious in-breeding (Thompson, 1991). Moreover, 
in some rivers, spawning by Atlantic sturgeon may not be contributing 
to population growth because of lack of suitable habitat and other 
stressors on juvenile survival and development.
    The concept of a viable population able to adapt to changing 
environmental conditions is critical to Atlantic sturg