[Federal Register: January 29, 2003 (Volume 68, Number 19)]
[Proposed Rules]
[Page 4433-4441]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr29ja03-26]
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DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
50 CFR Parts 223 and 224
[I.D. 122302B]
Endangered and Threatened Wildlife and Plants; 12-Month Finding
on a Petition to List North American Green Sturgeon as a Threatened or
Endangered Species
AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA), Commerce.
ACTION: Notice of petition finding and availability of a status review
document.
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SUMMARY: NMFS has completed an Endangered Species Act (ESA) status
review for the North American green sturgeon (Acipenser medirostris).
After reviewing the available scientific and commercial information,
NMFS has determined that the petitioned species is comprised of two
distinct population segments (DPSs) that qualify as species under the
ESA, but that neither DPS warrants listing as a threatened or
endangered species at this time. Because of remaining uncertainties
about their population structure and status, NMFS is adding both DPSs
to the agency's list of candidate species and will re-evaluate their
status in 5 years provided sufficient new information becomes available
indicating that a status review update is warranted.
DATES: The finding announced on this document was made on January 23,
2003.
ADDRESSES: The North American green sturgeon status review and list of
references are available by submitting a request to the Assistant
Regional Administrator, Protected Resources Division, Southwest Region,
NMFS, 501 West Ocean Blvd., Suite 4200, Long Beach, CA 90802-4213, or
the Assistant Regional Administrator, Protected Resources Division,
Northwest Region, NMFS, 525 NE Oregon Street, Suite 500, Portland, OR
97232. The status review and other reference materials regarding this
determination can also be obtained via the Internet at: http://www.nmfs.noaa.gov
.
FOR FURTHER INFORMATION CONTACT: Craig Wingert, NMFS, Southwest Region
(562) 980-4021, Scott Rumsey, NMFS, Northwest Region (503) 872-2791, or
David O'Brien, NMFS, Office of Protected Resources (301) 713-1401.
SUPPLEMENTARY INFORMATION:
Petition Background
On June 12, 2001, NMFS received a petition from the Environmental
Protection Information Center, Center for Biological Diversity, and
WaterKeepers Northern California requesting that NMFS list the North
American green sturgeon (Acipenser medirostris) as either an endangered
or threatened species under the ESA, and that critical habitat be
designated for the species concurrently with any listing determination.
[[Page 4434]]
The petition noted that the green sturgeon is a recognized species,
but also indicated that until recently, geographic variation in the
species had received little attention. Although Russian and Asian forms
of the green sturgeon are morphologically similar to the North American
form, the petitioners cited genetic evidence that demonstrates
differences between the Asian and North American forms and suggesting
they are two distinct species. In this petition, therefore, the use of
A. medirostris referred to the North American population of the green
sturgeon. The petitioners also noted that the stock structure of this
species is poorly known as well, and that there may prove to be DPSs
within this biological species as new data are gathered and analyzed.
The petitioners indicated that the only remaining spawning
populations of the North American green sturgeon are in the Sacramento
and Klamath River basins in California and possibly the Rogue River,
Oregon. The petitioners also suggest that the spawning population in
the Klamath River basin is larger than the population in the Sacramento
River basin. Running-ripe adults and young of the year have been
observed in the Rogue River, but exact spawning locations have not been
confirmed. The petitioners also stated that green sturgeon apparently
no longer spawn in the Eel River, the South Fork Trinity River, and the
San Joaquin River in California. The petitioners also cited recent
declines in green sturgeon in the Umpqua River in Oregon and the Fraser
River in Canada. The petitioners cite Musick et al. (2000) as
indicating that each of the known or suspected spawning populations of
green sturgeon presently contain a few hundred mature females at most.
The petitioners concluded that the North American green sturgeon is
at a high risk of extinction because of the reduced number and size of
spawning populations, ongoing threats to the species from the loss and/
or degradation of habitat particularly in those river systems where
they are known or thought to spawn, and continuing impacts to the
species from harvest in sport fisheries or as bycatch in other
fisheries (e.g. commercial white sturgeon fishery). Specific concerns
regarding habitat loss and degradation cited by the petitioners include
the construction of dams and operation of large scale water projects in
the Sacramento, Klamath River and other coastal systems, and logging,
agriculture, mining, road construction and urban development in coastal
watersheds. With respect to fisheries impacts on green sturgeon, the
petitioners cited fisheries that occur in coastal Washington and the
Columbia River which focus on white sturgeon or salmon but take green
sturgeon as a bycatch. Of particular concern is the potential bycatch
of pre-reproductive individuals in these fisheries, particularly if
this harvest is supported by the spawning populations that exist in the
Klamath and Sacramento River basins.
NMFS evaluated the information provided or cited in the petition
and also reviewed other information readily available to agency
scientists on issues related to the distribution, abundance, and
threats to the petitioned species. On December 14, 2001, NMFS published
a 90-day finding (66 FR 64793) that the petition presented substantial
information that listing North American green sturgeon under the ESA
may be warranted, and announced the initiation of a review of the
biological status of the species.
To ensure that the status review was complete and based on the best
available scientific and commercial data, the 90-day finding also
requested information and comments from the public concerning the
status of North American green sturgeon (66 FR 64793). In addition,
NMFS specifically requested information and comments on green sturgeon
from State and Tribal co-managers in California, Oregon, and
Washington. NMFS requested information on: (1) biological or other
relevant data that may help identify DPSs of this species (e.g., age
structure, genetics, migratory patterns, morphology, etc.); (2) the
range, distribution, and abundance of this species, including
information on the spawning populations of the species; (3) current or
planned activities and their possible impact on this species (e.g.,
harvest impacts, habitat changes or alterations, etc.); and (4) efforts
being made to protect this species in California, Oregon, Washington
and Canada. NMFS also requested quantitative evaluations describing the
quality and extent of freshwater, estuarine and marine habitats for
this species, as well as information on areas that may qualify as
critical habitat in California, Oregon, and Washington. For areas
potentially qualifying as critical habitat, NMFS requested information
describing (1) the activities that affect the area or could be affected
by the designation, and (2) the economic costs and benefits of
additional requirements of management measures likely to result from
the designation.
NMFS assembled a Biological Review Team (BRT) comprised of staff
from the agency's Southwest Fisheries Science Center, Northwest
Fisheries Science Center, and the U.S. Geological Survey. The BRT has
reviewed the best available scientific and commercial information
pertaining to green sturgeon from California through the Pacific
Northwest and prepared a status review for the species (NMFS, 2002).
This document summarizes the principal results of the green sturgeon
status review. Copies of the BRT status review report and other
documents relevant to this review are available online. Paper copies
are available upon request (see ADDRESSES).
Biology and Life History of Green Sturgeon
The green sturgeon (A. medirostris) is the most widely distributed
member of the sturgeon family Acipenseridae. Like all sturgeon species
it is anadromous, but it is also the most marine oriented of the
sturgeon species. The only recently-documented green sturgeon spawning
locations are in the Klamath, Sacramento, and Rogue rivers along the
west coast of North America. However, green sturgeon are known to range
in nearshore marine waters from Mexico to the Bering Sea and are
commonly observed in bays and estuaries along the coast with
particularly large concentrations entering the Columbia River estuary,
Willapa Bay, and Grays Harbor during the late summer (Moyle et al.,
1992). The reasons for these concentrations are unclear, but do not
appear to be related to spawning or feeding.
Sturgeons in general have a life history that is susceptible to
overharvesting and a number of species have some kind of protection or
special status. The green sturgeon has a status designation of Special
Concern in Canada (Houston 1988) because it has characteristics that
make it particularly sensitive to human activities or natural events.
Sakhalin sturgeon (A. mikadoi), a species that was at one time
synonymized with green sturgeon, is extirpated throughout Japan, Korea,
and China. In Russia the species is reduced in range to the Tumnin
River where there is a hatchery. In the United States, there are five
sturgeon species listed as threatened or endangered under the ESA:
Shortnose sturgeon (A. brevirostrum); pallid sturgeon (Scaphirhynchus
albus); Gulf sturgeon (A. oxyrinchus); white sturgeon, Kootenai River
population (A. transmontanus); and Alabama sturgeon (S. suttkusi). More
detailed information on the geographic distribution, spawning, early
life history, ocean residence, age and growth, and feeding
[[Page 4435]]
habits of green sturgeon are presented below.
Distribution. San Francisco Bay and its associated river systems
contain the southern-most spawning population of green sturgeon. White
sturgeon supports a large fishery in this area, particularly in San
Pablo Bay, which has been extensively studied by California Department
of Fish and Game (CDFG) since the 1940's. While green sturgeon are not
common, they are collected incidentally in a white sturgeon trammel net
monitoring program during most years in numbers ranging from 5 to 110
fish. Green sturgeon juveniles are found throughout the Delta and San
Francisco Bay.
Green sturgeon adults and juveniles occur throughout the upper
Sacramento River. Green sturgeon are reported to spawn in the Feather
River, but this has not been substantiated. Green sturgeon spawning
occurs predominately in the upper Sacramento River. Juvenile sturgeon
have been taken annually in trapping operations at the RBDD (1995-2001)
and at the Glenn-Colusa Irrigation District pumping facility as part of
a monitoring program (1986-2001). All larval and juvenile sturgeon
caught at these locations are assumed to be green sturgeon because
juveniles collected at these sites and grown to identifiable size were
green sturgeon. There is no documentation of green sturgeon spawning in
the San Joaquin River at present, but there may have been spawning
there before construction of large-scale hydropower and irrigation
development. Young green sturgeon have been taken occasionally in the
Santa Clara Shoal area in the San Joaquin delta but these fish likely
originated from elsewhere, most likely the Sacramento River (CDFG
2002).
Green sturgeon also occur in the coastal waters of the Pacific
Ocean off California and in coastal rivers. Small numbers have been
taken in both Tomales Bay and Bodega Bay and a single fish has been
taken from the Noyo River. They are regularly taken in small numbers in
Humboldt Bay, and have been caught in coastal waters and in estuaries
from Arcata Bay to the Oregon border. Small numbers of both adult and
juvenile green sturgeon have been observed in the Eel River.
The largest spawning population of green sturgeon is thought to
occur in the Klamath River on the north coast of California, but there
are no direct estimates of green sturgeon abundance. Adults are
captured in the salmon gill net fisheries conducted by the Yurok and
Hoopa Indian tribes and adults occur upstream in the Klamath to a
natural migration barrier at Ishi Pishi Falls (rkm 107). Juvenile green
sturgeon are captured each year on the Klamath River and have also been
found in the lower portion of the Salmon River which is a tributary to
the Klamath River. Adults occur in the Trinity River, a major tributary
to the Klamath River, to Gray's Falls (rkm 69), but spawning can only
be confirmed up to the Willow Creek trap (rkm 40). Moyle et al. (1992)
reported no evidence of spawning in the South Fork of the Trinity
River.
The Rogue River in Oregon was recently confirmed as a third
spawning area for green sturgeon (Erickson et al., 2001, Rien et al.,
2001). Based on tracking of radio-tagged adults captured in the
estuary, extended holding sites were identified that have been
associated with spawning in other species of sturgeon. Juvenile fish
are taken in beach seining efforts in the estuary (Rien et al., 2001).
Green sturgeon adults are taken in almost all of the Oregon coastal
estuaries from the Chetco River to Nehalem Bay (EPIC et al., 2001).
During white sturgeon tagging projects in Coos Bay (Coos River),
Winchester Bay (Umpqua River), Yaquina Bay (Yaquina River), and
Tillamook Bay (Tillamook River) green sturgeon have been captured and
tagged; however, no recoveries have been reported (ODFW 2002).
The Columbia River has supported a large white sturgeon fishery for
many years in which green sturgeon are taken as bycatch. In the mid
1930's before Bonneville dam, green sturgeon were found up to the
Cascade Rapids. Green sturgeon are presently found up river to the
Bonneville Dam (rkm 235), but are predominately found in the lower 60
rkm. Tagging studies indicate a substantial exchange of fish between
the Columbia River and Willapa Bay (WDFW 2002a). Willapa Bay, along
with the Columbia River and Grays Harbor, is one of the estuaries where
green sturgeon concentrate in summer. Generally, green sturgeon are
more abundant than white sturgeon in Willapa Bay (Emmett et al., 1991).
Grays Harbor in Washington is the northernmost estuary with green
sturgeon summer concentrations and there are both tribal and commercial
fisheries that take green sturgeon. There are no records of juveniles
from Grays Harbor. Green sturgeon occur sporadically in small numbers
throughout coastal Washington (WDFW 2002a) and are routinely
encountered in the coastal Washington trawl fishery as minor incidental
catch (WDFW 2002b). Occasionally, green sturgeon are caught in small
coastal bays and estuaries during tribal salmon fisheries. A few green
sturgeon are recovered in Puget Sound as incidental harvest (mostly
trawl fisheries).
Green sturgeon occur in small numbers along the western coast of
Vancouver Island (Houston 1988) and the Skeena River. Historically,
green sturgeon were not uncommon in the Fraser River (EPIC et al.,
2001). Since the collapse of the Fraser River white sturgeon fishery,
however, green sturgeon are only taken there occasionally.
Spawning. Green sturgeon are thought to spawn every 3 to 5 years
(Tracy 1990). Their spawning period is March to July, with a peak in
mid-April to mid-June (Moyle et al., 1992). Mature males range from
139-199 cm in fork length (FL) and 15 to 30 years of age (VanEenennaam
2002). Mature females range from 157-223 cm FL and 17 to 40 years of
age. Most of the spawning males are 160-170 cm FL and 17-18 years old,
while most of the spawning females are 182-192 cm FL and 27-28 years
old.
Green sturgeon spawning occurs in deep pools or ``holes'' in large,
turbulent river mainstems (Moyle et al., 1992). Specific spawning
habitat preferences are likely large cobble substrates, but may range
from clean sand to bedrock substrates as well. Eggs are likely
broadcast over the large cobble substrates where they settle into the
space between the cobble. Green sturgeon females produce 60,000-140,000
eggs (Moyle et al., 1992) and they are the largest eggs (diameter 4.34
mm) of any sturgeon species (Cech et al., 2000). Temperatures above 20
C are lethal to green sturgeon embryos (Cech et al., 2000).
Green sturgeon spawning has only been documented in the Klamath,
Sacramento (Moyle et al., 1992, CDFG 2002) and Rogue (Erickson et al.,
2001, Rien et al., 2001) rivers in recent times. The Klamath Basin is
thought to support the largest green sturgeon spawning population
(Moyle et al., 1992). In the Klamath River, breaching and other
suspected sturgeon courtship behaviors have been observed in ``The
Sturgeon Hole'' upstream of Orleans (rkm 96). Larvae and juveniles are
caught in the Big Bar trap (rkm 80) on the Klamath and in the Willow
Creek trap (rkm 40) on the Trinity. Numbers at both traps have a peak
in July (Healey 1973).
In the Sacramento River, green sturgeon spawn in late spring and
early summer above Hamilton City and perhaps as far upstream as Keswick
Dam (CDFG 2002). The opening of the Red Bluff Diversion Dam (RBDD)
gates to improve winter-run chinook upstream and downstream passage is
believed to have provided a substantial
[[Page 4436]]
increase in spawning habitat for green sturgeon in the upper Sacramento
River. The gates were first opened in 1986 and the current pattern of
operation began in 1992-93. Juvenile green sturgeon are taken in traps
at the RBDD and the Glenn Colusa Irrigation District's (GCID) facility
in Hamilton City, primarily in the months of May through August. Peak
counts occur in the months of June and July.
Green sturgeon spawning has been recently documented in the Rogue
River (Erickson et al., 2001, Rien et al., 2001). Adult fish were
radio-tagged in the estuary during May-June 2000. After release, tagged
ripe fish moved up the Rogue River to spawn, while non-reproductive
fish remained close to the tagging site. Spawning fish spent more than
6 months in freshwater and traveled as far as rkm 39. All tagged
individuals emigrated from freshwater during fall and winter when water
temperatures fell below 10 C. Juvenile green sturgeon have been taken
in beach seines in the Rogue River estuary from April until the end of
November (Rien et al., 2001).
Apparently, green sturgeon no longer spawn in some river systems
where they once did (CDFG 2002). Juvenile green sturgeon were captured
in the Eel River in traps at Rio Dell (rkm 20) and Dos Rios (rkm 191)
during the period from 1967 to 1970 (Puckett 1976). Single or small
numbers of adult green sturgeon are also observed periodically in the
Eel River. Similarly, green sturgeon are reported to have spawned in
the South Fork Trinity River, but apparently no longer do so due to
extensive sedimentation from the 1964 flood (Moyle et al., 1992). The
validity of reports of green sturgeon spawning in the Umpqua River is
unclear (Lauman et al., 1972) and the possibility of current spawning
activity is being investigated (ODFW 2002).
Early Life History. Green sturgeon larvae first feed at 10 days
post hatch, and metamorphosis to the juvenile stage is complete at 45
days. Larvae grow fast, reaching a length of 66 mm and a weight of 1.8
g in 3 weeks of exogenous feeding. Juveniles averaged 29 mm at the peak
of occurrence in June-July at the RBDD fish trap and 36 mm at their
peak abundance in July at the GCID trap. These growth rates are
consistent with rapid juvenile growth to 300 mm in 1 year and to over
600 mm within 2-3 years for the Klamath River (Nakamoto et al., 1995).
Juveniles appear to spend 1 to 3 years in freshwater before they enter
the ocean (Nakamoto et al., 1995).
Ocean Residence. Green sturgeon disperse widely in the ocean after
their out-migration from freshwater (Moyle et al., 1992). Tagged green
sturgeon from the Sacramento and Columbia Rivers are primarily captured
to the north in coastal and estuarine waters, with some fish tagged in
the Columbia being recaptured as far north as British Columbia (WDFW
2002a). While there is some bias associated with recovery of tagged
fish through commercial fishing, the pattern of a northern migration is
supported by the large concentration of green sturgeon in the Columbia
River estuary, Willapa Bay, and Grays Harbor which peaks in August.
These fish tend to be immature; however, mature fish and at least one
ripe fish have been found in the lower Columbia River (WDFW 2002a).
Genetic evidence suggests that Columbia River green sturgeon are a
mixture of fish from at least the Sacramento, Klamath, and Rogue Rivers
(Israel et al., 2002). The reasons for the concentration of green
sturgeon in Oregon and Washington estuaries during the summer are
unknown as there is no known spawning in these rivers and all stomachs
examined to date have been empty (Beamesderfer 2000).
Age and Growth. Green sturgeon is a long-lived, slow-growing
species as are all sturgeon species (Nakamoto et al., 1995, Farr et
al., 2002). Size-at-age is consistently smaller for fish from the
Klamath River (Nakamoto et al., 1995) in comparison to fish from Oregon
until around age 25, but thereafter the pattern is reversed. This could
be the result of actual differences in growth or in ageing techniques.
The asymptotic length for Klamath fish of 218 cm is close to the
maximum observed size of 230 cm reported by Moyle et al. (1992), but
substantially larger than for fish in Oregon (females 182 cm, males 168
cm).
Feeding. Little is known about green sturgeon feeding. Adults in
the Sacramento-San Joaquin delta feed on benthic invertebrates
including shrimp, mollusks, amphipods, and even small fish (Moyle et
al., 1992). Juveniles in the Sacramento-San Joaquin Delta feed on
opossum shrimp and amphipods (Radtke 1966). One hundred and twenty-one
green sturgeon stomach samples from the Columbia River gill-net fishery
were empty with the exception of one fish, while all white sturgeon
stomachs contained digested material (ODFW 2002).
Consideration as a ``Species'' Under the ESA
To qualify for listing as a threatened or endangered species the
petitioned North American green sturgeon must be considered a species
under the ESA. Section 3(16) of the ESA (16 U.S.C. 1532(16)) expands
the definition of a ``species'' under the ESA to include any subspecies
or any ``distinct population segment (DPS) of any species of vertebrate
fish or wildlife which interbreeds when mature.'' On February 7, 1996,
the U.S. Fish and Wildlife Service and NMFS adopted a policy to clarify
their interpretation of the phrase ``distinct population segment of any
species of vertebrate fish or wildlife'' for purposes of listing,
delisting, and reclassifying species under the ESA (61 FR 4722). This
joint policy identifies two elements that must be considered when
making DPS determinations: (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 species or subspecies to which it belongs.
According to the joint policy, a population segment 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; or (2) it is delimited by international
governmental boundaries across which there is a significant difference
in exploitation control, habitat management, or conservation status.
Quantitative measures of genetic or morphological discontinuity may
provide evidence of this separation.
The joint policy states that the following are some of the
considerations that may be used when determining the significance of a
population segment to the taxon to which it belongs: (1) persistence of
the discrete population in an unusual or unique ecological setting for
the taxon; (2) evidence that the loss of the discrete population
segment would cause a significant gap in the taxon's range; (3)
evidence that the discrete population segment represents the only
surviving natural occurrence of a taxon that may be more abundant
elsewhere; or (4) evidence that the discrete population segment has
marked genetic differences from other populations of the species.
Species Status and DPS Structure
Species Status. Green sturgeon that occur within U.S. and Canadian
waters are a geographically isolated and genetically distinct species.
The North American form was initially considered conspecific with the
previously described Asian species, Sakhalin sturgeon (A. mikadoi), and
the two forms were synonymized (Berg, 1948). More recent molecular data
on three mitochondrial genes, however, show great differences between
the North
[[Page 4437]]
American and Asian forms of green sturgeon (Birstein and DeSalle,
1998), and consequently, these two forms are now considered separate
species.
The petitioned action requested that North American green sturgeon
be listed as a threatened or endangered species, but the petitioners
also recognized that this species could be comprised of multiple DPSs.
For this reason and because other sturgeon species have been divided
into multiple DPSs, NMFS' BRT assessed the best available scientific
information concerning the population structure of green sturgeon in
North America in an effort to determine whether or not the biological
species was comprised of one or more DPSs. Based on a review of the
best available scientific information, NMFS has determined that North
American green sturgeon are comprised of two populations that are both
discrete and significant as defined in the DPS policy and are therefore
DPSs. One is a northern DPS consisting of coastal populations ranging
from the Eel River northward. The second is a southern DPS that
includes any coastal or central valley populations south of the Eel
River, with the only known population being in the Sacramento River.
These DPSs and the information used to characterize them are summarized
below, and discussed in greater detail in the green sturgeon status
review (NMFS 2002).
Discreteness: Genetic data were analyzed from 66 green sturgeon
sampled from the Klamath River in 1998, 46 fish sampled from San Pablo
Bay in 2001, 15 sampled from the Rogue River in 2000, and 29 sampled
from the Columbia River estuary in 1995. The analysis on this genetic
data, while preliminary, suggest that green sturgeon from the Klamath
River are genetically distinct from fish in San Pablo Bay, and that
green sturgeon from the Klamath and Rogue River are similar to each
other (Israel et al., 2002). Green sturgeon from the Columbia River
appear to be a mixture of fish from the San Pablo Bay, Klamath, and
Rogue populations. Israel et al. (2002) suggest that the genetic data
indicate that spawning could be occurring in some other unknown
locations; however, this preliminary conclusion could change if larger
samples were analyzed or if samples were collected from multiple years.
While preliminary, the best available genetic data indicates that there
are substantial genetic differences at least between the geographically
separated Klamath River and San Pablo Bay populations of green
sturgeon.
Sturgeon species exhibit fidelity to their spawning sites so they
have a general pattern of multiple DPSs. Sturgeon are known to have
strong homing capabilities which leads to high spawning site fidelity
(Bemis and Kynard, 1997). Because preliminary genetic data indicate
that the Sacramento River population is different from the Klamath and
Rogue River populations, and because sturgeon tend to exhibit high
spawning site fidelity, NMFS has determined that the two green sturgeon
populations are ``discrete'' as defined in the DPS policy.
Significance: The genetic information described above indicates
that the northen and southern populations are ``significant'' as
defined in the DPS policy. In addition to the genetic information,
there is other information indicating that these DPSs are significant.
First, each DPS occupies unusual or unique ecological settings for the
species as a whole. This is evidenced by the fact that spawning
populations of each DPS are found in separate and distinct
Environmental Protection Agency ecoregions that have been identified
based on soil content, topography, climate, potential vegetation, and
land use (Omernik 1987). The geographic range of the northern DPS
occurs largely within the Coastal Range ecoregion which extends from
the Olympic Peninsula southward through the Coast Range and Klamath
Mountains to the San Francisco Bay area. In contrast, the southern DPS
occurs largely within the Central California Valley ecoregion which
includes the Sacramento and San Joaquin Rivers. Second, the loss of
either of these DPSs would result in a significant gap in the range of
the species given the known distribution of spawning populations.
The identification of two DPSs and the geographic separation of the
two DPSs at the Eel River should be considered provisional and subject
to revision as more genetic and life history information is gathered on
green sturgeon. Although NMFS believes that the green sturgeon is
comprised of at least these two DPSs, additional DPSs may be delineated
when more genetic and life history information is collected and
analyzed. Similarly, the Eel River boundary between these two DPSs is
based largely on geography and may be modified based on new
information.
Status of Green Sturgeon DPSs
In assessing the status of the northern and southern DPSs, NMFS
evaluated the available literature, information obtained in response to
the 90-day finding request for information, and both qualitative and
quantitative information provided by state and Tribal co-managers from
California, Oregon, and Washington. The quantitative information was
primarily time series of harvest (catch and catch-per-unit-effort
(CPUE)) data from fishery agencies in Oregon and Washington, and from
Tribal fishery managers in the Klamath River basin.
Northern Green Sturgeon DPS
Information relevant to assessing the abundance and/or population
trends of green sturgeon in this DPS is limited. The status review for
green sturgeon examined fisheries harvest data from the Yurok tribal
fishery in the Klamath River and the commercial sturgeon fishery in the
Columbia River in an effort to assess trends in abundance over time and
population status (NMFS 2002). The time series of catch and CPUE data
for the Yurok tribal fishery was considered the most representative
available population measure for green sturgeon in general and this DPS
in particular because the data are based on a spawning population in
the DPS rather than a summer concentration of non-spawning fish from a
mixture of spawning populations such as is the case in the Columbia
River. Both data series are fishery-dependent and suffer from problems
associated with changing regulations and effort levels.
Catch and CPUE data are available for the Yurok tribal fishery for
the period 1984-2001, and it is the data set least impacted by
regulatory changes. A qualitative examination of the data suggests that
catch has increased slightly over time and that CPUE is stable or has
slightly decreased over time. However, these trends are not
statistically significant. The length-frequency data of harvested green
sturgeon was also examined to determine if there was any evidence that
harvest was affecting the size structure of the population. Although
the sample sizes were small, there was no evidence of any trend in the
available data suggesting that larger fish were being removed from the
population or that the size structure of the population has been
altered by this or other fisheries.
The Columbia River commercial harvest data represents the longest
available green sturgeon time series, but it is difficult to interpret
since the harvest occurs on a summer concentration of non-spawning fish
that are thought to originate from multiple spawning populations.
Regulations were significantly modified in 1993, so the analysis of
trends was only conducted on catch data from 1960-1992. Catch over this
time period may have been affected not only by changes in regulations
and effort but also by
[[Page 4438]]
unknown factors controlling the summer concentration of green sturgeon
in the Columbia River. The catch data were analyzed to determine if
there were any trends in data and if they were significant. Length
frequency of the catch data was also examined over the period of 1985-
2001 to see if the fishery was affecting the size structure of fish
that concentrate in the Columbia River. Analysis of the data suggests
that catch in the Columbia River has increased slightly over time;
however, the trend was not statistically significant. In contrast, Rein
(2002b) analyzed CPUE data for green sturgeon in the lower Columbia
River commercial fishery over the same period of time (1981-1993) and
found there was a statistically significant increasing trend. There was
little evidence of a trend in the length-frequency distributions of
catch over time. However, there does appear to have been an increase in
the average length of green sturgeon taken in the fishery over the past
few years, possibly suggesting that a strong year class is moving
through the fishery.
The status review identified potential risk factors for the
northern green sturgeon DPS including harvest bycatch in several
fisheries, the concentration of spawning in the Klamath River, the loss
of historical spawning habitat, and the lack of adequate abundance and
population trend data (NMFS, 2002). While there is some information
relevant to harvest bycatch, limited information is available about the
distribution of historical and current spawning activity, and the loss
of spawning habitat. The lack of adequate abundance and population
trend data is of concern because it is difficult to assess the status
of the population without such data. As a result, there is considerable
uncertainty regarding the extent to which these factors affect the
overall level of risk faced by this DPS.
The Klamath River is thought to support most of the total spawning
population in this DPS and there is concern that this could increase
the vulnerability of the DPS to catastrophic events. However, the
extent to which spawning is concentrated in the Klamath River is not
well documented and there is limited information on the extent and
magnitude of spawning elsewhere in the DPS. Recent information, for
example, has documented spawning in the Rogue River (Rein et al., 2001)
and the possibility of spawning in the Umpqua River is also being
investigated (ODFW 2002). Further research and monitoring in these and
other coastal watersheds may provide new information about the
magnitude and geographical extent of current spawning within this DPS
and the importance of the spawning population in the Klamath River.
Historical accounts, and what little data are available, suggest there
has been a loss of spawning habitat in the Eel River and South Fork
Trinity Rivers due to anthropogenic changes and natural events that
increased sedimentation (CDFG, 2002). At the same time, it is uncertain
to what extent the loss or reduction of spawning in the Eel and South
Fork Trinity Rivers has affected this DPS or the extent to which it
places the DPS at greater risk since there is virtually no information
documenting the magnitude and extent of spawning that historically
occurred in either system. Although spawning apparently no longer
occurs in the South Fork Trinity, there is recent evidence of limited
green sturgeon spawning in the Eel River based on the collection of
both adult and juvenile fish in the mid 1990s (CDFG, 2002).
The status review examined the available harvest bycatch data in an
effort to assess the effects of harvest on green sturgeon in this DPS
and in general, but concluded it was not possible to directly assess
harvest impacts because of two factors. First, most of the harvest
occurs on summer concentrations of fish in the Columbia River and
coastal Washington estuaries that are comprised of fish from a mixture
of spawning populations and both DPSs. Second, there is no estimate of
the size for any of the known spawning populations that occur in either
DPS. Although direct assessment of harvest impacts on this DPS may not
be possible with the available data, a qualitative assessment of green
sturgeon bycatch data for various fisheries since the mid 1980s
suggests that the impacts to green sturgeon from harvest bycatch have
been greatly reduced in recent years.
Harvest of green sturgeon occurs almost entirely as bycatch in
commercial fisheries for white sturgeon in Oregon and Washington, as
well as a variety of smaller tribal fisheries (e.g. Klamath River
tribal fisheries). Green sturgeon harvest data for these fisheries were
summarized in the status review for the years 1985-2001, and over this
period the vast majority of the total harvest was taken in the Columbia
River sport and commercial fisheries (51 percent) and the various
Washington coastal fisheries (28 percent). The remainder of the total
harvest occurred in the coastal Oregon fisheries and the Klamath River
tribal fisheries. Since the mid 1980s, the total annual harvest of
green sturgeon in all of these fisheries has declined nearly six fold
from approximately 6,870 fish/year in 1985-1989 to approximately 1,190
fish/year in 1991-2001 (Table 1 in NMFS 2002). In 2001, the total
harvest in all fisheries declined to less than 800 fish, with
approximately equal numbers of fish taken in the Columbia River,
coastal Washington, and Klamath River fisheries. This overall decline
in green sturgeon harvest has been driven principally by a major
reduction in the harvest from the Columbia River and Washington coastal
fisheries since the mid 1990s.
The average length of green sturgeon caught in the Columbia River
commercial fishery has been increasing since 1990, with the largest
average size of fish occurring in the last five years. This trend may
indicate a larger average size of fish due to reduced exploitation, a
strong year-class moving through the fishery, or a reduction of small
fish due to reduced or failed recruitment.
Much of the harvest reduction in recent years is due to
increasingly restrictive regulations in the Columbia River fisheries
(Appendix 1, Tables 1 and 2 in NMFS 2002). The Columbia River fishery
is currently managed through a joint Washington and Oregon accord to
manage white sturgeon. Probably the most important regulation for
protecting sturgeon was the introduction of slot limits starting in
1950 for both the sport and commercial fisheries. Beginning in 1950 and
continuing through 1997-98 when the slot limits were last changed, they
have become increasingly restrictive and protective of both green and
white sturgeon. The Columbia River sturgeon fishery is currently
operating under a March 2000 agreement covering a three-year period
through 2002. The green sturgeon regulations under this agreement
include: a recreational size limit of 42-60 inches (107-152 cm) with
one fish per day and 10 fish per year bag limits, with barbless hooks
required; a commercial size limit of 48-66 inches (122-168 cm); and no
green sturgeon-only commercial seasons (green sturgeon are only taken
as bycatch during white sturgeon seasons, provided the green sturgeon
catch does not exceed recent harvest levels). Commercial bycatch of
green sturgeon occurs predominantly during the early fall (August)
salmon and white sturgeon fisheries, when the green sturgeon have
migrated into the estuary and lower mainstem of the Columbia River.
In 2001, sturgeon retention was prohibited during the early-fall
target chinook commercial season after the preseason catch expectation
for white sturgeon was exceeded in early August. Sturgeon retention was
prohibited in
[[Page 4439]]
mainstem commercial fisheries through the remainder of the fall fishing
period. White sturgeon population estimates for 2002 did not increase
as expected, and in December of 2001 the Compact adopted reduced catch
guidelines for 2002 as a management buffer and to compensate for catch
overages that occurred in 2001. In 2002, the Compact prohibited
retention of green sturgeon during August fisheries and allowed
retention during September and October fisheries. This management
action provided flexibility for shaping September and October salmon
fisheries and allowed the commercial fishery access to their allocation
of white sturgeon without any target sturgeon seasons, further
minimizing green sturgeon bycatch. The Compact will meet in January
2003 to review its sturgeon fishery management agreement and it is
expected that continued efforts will be taken to minimize green
sturgeon bycatch.
Ocean and coastal estuarine fisheries in Washington and Oregon
accounted for approximately 28 percent and 8 percent, respectively, of
the total green sturgeon harvest bycatch in the period between 1985-
2001. Since the mid to late 1990's, however, the overall catch of green
sturgeon in these fisheries has also declined substantially, most
likely due to changes in fishing regulations. White and green sturgeon
fisheries in Oregon coastal areas are managed under size and bag limit
regulations consistent with the lower Columbia River regulations.
Non-tribal harvest impacts on green sturgeon in coastal rivers of
California are considered to be minimal (CDFG, 2002). Commercial
fishing for green sturgeon (and white sturgeon) has been prohibited
throughout the state since the early 1900s. Recreational fishing for
green sturgeon has been prohibited since the early 1990s in virtually
all coastal watersheds where green sturgeon are known to occur from the
Eel River northward to the Oregon border, including the Klamath-Trinity
basin. The Klamath River tribal (Yurok and Hoopa Tribes) fisheries
accounted for about 8 percent of the total green sturgeon harvest that
occurred between 1985-2001, with an average catch of approximately 260
fish per year. These Tribal fisheries do impact a spawning population
in the Klamath River, but the available data for the Yurok Tribal
fishery show that both catch and CPUE have been very stable since 1985,
with no evidence of a decline. There is no evidence from the available
length-frequency data for harvested green sturgeon that larger fish
have been removed from the population or that the size structure of the
population has been altered by this or other fisheries.
Conclusion: The available population information for green sturgeon
in the northern DPS does not provide any evidence that the abundance of
green sturgeon in this DPS is declining. In particular, the fishery-
dependent harvest data from the Yurok tribal fishery show no evidence
that catch or CPUE are declining, or that large fish are being removed
from that spawning population. Despite this information, NMFS' BRT was
uncertain about the status of green sturgeon in this DPS because no
direct fisheries-independent population estimates were available. For
this reason, the BRT believes it is essential that immediate efforts be
undertaken to implement direct monitoring of green sturgeon in this
DPS. There are some risk factors of potential concern for this DPS,
most notably bycatch harvest in various fisheries; however, there is
uncertainty about the overall level of risk facing this DPS. In the
case of harvest bycatch for which there is the most information, it is
not possible to directly assess the impact of harvest on green sturgeon
in this DPS. Nevertheless, the available data shows that overall green
sturgeon harvest has declined substantially since the mid 1980s due to
increasingly restrictive harvest management measures, suggesting that
risk from harvest has been also reduced. Although the risk to green
sturgeon from harvest bycatch may be declining, NMFS believes it may be
prudent for fisheries managers to continue recent conservative
management measures as well as consider additional harvest protections
until population monitoring information can be obtained to assess the
status of this DPS with greater certainty. Based on a review of the
best available information, NMFS concludes that the northern green
sturgeon DPS is not presently in danger of extinction nor is it likely
to become so in the foreseeable future.
Southern Green Sturgeon DPS
The only data relevant to assessing the abundance and/or population
trends of green sturgeon in this DPS are estimates of green sturgeon
abundance made by the California Department of Fish and Game in San
Pablo Bay incidental to monitoring of white sturgeon (CDFG, 2002).
Tagging experiments have been conducted irregularly since 1954, but
since 1990 tagging has been conducted for two years consecutively and
then the next two are skipped. Over this period, a total of 536 green
sturgeon were captured and 233 fish were tagged. The green sturgeon
estimate is obtained by multiplying the ratio of legal-size (earlier
minimum slot limits of 102 cm) green sturgeon to legal-size white
sturgeon caught in the tagging program by the legal-size white sturgeon
population estimate. Although this is a fishery-independent estimate of
green sturgeon abundance, there are a number of problems associated
with these estimates; the most important being the assumption that both
species are equally vulnerable to the sampling gear. Since green
sturgeon concentrate in estuaries only during the summer and white
sturgeon remain in estuaries year round, the temporal and spatial
vulnerabilities of the two species are likely different. In addition,
the estimate is based on a summer concentration of fish rather than a
spawning population, and varying levels of tag recovery effort.
The status review examined the available time series of these
population estimates qualitatively and also looked for statistically
significant trends in the data. A qualitative examination of the time
series suggests abundance has been stable, except for a substantial
increase in the 2001 abundance estimate. The 2001 abundance estimate
was 8,421 fish which is approximately four times higher than any
previous estimate. Estimates for the years prior to 2001 range from
several hundred to approximately 2,000 fish (see Figure 11 and Table 2
in NMFS 2002). The data suggest an increasing trend in green sturgeon
abundance, but the increase was not statistically significant even with
the large increase in the 2001 estimate. Although the sample sizes are
small, the average size of green sturgeon tagged as part of this
population estimation program in San Pablo was generally stable and
showed no apparent trend over time.
NMFS' BRT identified several potential threats or risk factors for
the southern green sturgeon DPS (NMFS, 2002). These include: harvest
bycatch concerns; the concentration of spawning in the Sacramento River
and the apparent small population size; loss of spawning habitat, lack
of adequate population abundance data; potentially lethal water
temperatures for larval green sturgeon; entrainment by water projects
in the central valley; and the adverse effects of toxic materials and
exotic species. Although the BRT expressed concerns about these
potential risk factors, there is considerable uncertainty regarding
their significance or effects on the southern green sturgeon DPS.
Spawning in this DPS does appear to be concentrated in the upper
Sacramento River at present. Since the
[[Page 4440]]
early 1990s it appears that green sturgeon have expanded into
additional spawning habitat in the upper Sacramento above Hamilton City
due to the re-operation of the RBDD (CDFG, 2002). There is uncertainty
about the abundance of green sturgeon and the size of the spawning
population in the Sacramento River. The CDFG population estimates for
San Pablo Bay, which presumably include Sacramento River spawners, are
in the range of hundreds to thousands of fish, but there are several
problems with the estimates that make them difficult to interpret or
rely upon. Similarly, there are no historical estimates of spawning
population abundance available to make an assessment of the extent to
which spawning populations have declined. The lack of population
monitoring data is clearly problematic, but it is not a risk factor
directly affecting the status of the DPS.
According to the CDFG, there is no evidence that green sturgeon
historically spawned in the San Joaquin River and juveniles that have
been found in the lower San Joaquin River are most likely from the
spawning population in the Sacramento River (CDFG, 2002). It is
uncertain whether green sturgeon ever spawned in the upper Sacramento
River above Shasta Dam, but CDFG has speculated that they may have
based on the apparent expansion of spawning above Hamilton City in the
early 1990s when RBDD was re-operated (CDFG, 2002). The most likely
loss of historical spawning habitat for green sturgeon in the central
valley may be in the Feather River as a result dam construction and
warm water releases (CDFG, 2002), but anecdotal evidence suggests that
adult green sturgeon still occur there in high flow years, presumably
for spawning. Based on this information, it is uncertain how much green
sturgeon spawning habitat historically occurred in the central valley
or how much has been lost, and whether or not lost spawning habitat is
a significant risk factor for this DPS.
The state and Federal pumping facilities in the Sacramento-San
Joaquin Delta export water from the Delta and in the process entrain
many fish species including juvenile green sturgeon which are salvaged
and returned to the Delta. Expanded estimates of salvage are made
annually by CDFG and these data have been collected and compiled since
1968 at the state facility and since 1981 at the Federal facility. The
status review qualitatively reviewed the expanded salvage data for the
available time series to determine whether there were any trends. The
data series indicates that salvage (an indicator of entrainment) has
varied substantially over time, but was much higher prior to the mid-
1980s. From the mid-1980s to present, salvage declined substantially at
both facilities and has remained very low thereafter. Limited length-
frequency data indicates that only juvenile green sturgeon were
salvaged at the two facilities. Interpretation of these data is
difficult since there have been problems with species identification
(distinguishing white and green sturgeon) and the expanded salvage
estimates are based on actual counts from brief sampling periods (CDFG
2002). Given the low level of entrainment and salvage that has occurred
since the mid-1980s and the problems with interpreting the available
data, it is uncertain to what extent water exports and the associated
entrainment of green sturgeon is a risk factor for this DPS. In the
case of white sturgeon, however, year class strength is related to
freshwater flows in late winter and spring rather than Delta exports
(CDFG 2002). If this is the case for green sturgeon, which is more
marine oriented than white sturgeon, then Delta exports are not likely
to be an important risk factor.
The introduction of exotic species in the San Francisco Bay estuary
is an ongoing problem, but the most likely effect on green sturgeon is
through changes in trophic interactions (CDFG, 2002). For example, the
overbite clam, which first was observed in the Bay in 1988, is now the
most common food item of white sturgeon and has been found in the diet
of green sturgeon (CDFG, 2002). This species may be replacing other
clam species in the diet of white and possibly green sturgeon, but it
is not possible to assess the impacts of such changes at present.
Assessing the impacts of such trophic changes and the extent to which
they increase risks to green sturgeon in this DPS will require
additional information on the comparative trophic benefits of these new
prey and information on the extent to which they bioaccumulate
contaminants.
There is no specific information available regarding contaminant
loads or impacts on green sturgeon, although there is information on
contaminant loads for white sturgeon (CDFG 2002). For example, there is
evidence that white sturgeon may have contained high Polychlorinated
Biphenyl (PCB) levels in the past (Kohlhorst, 1980), though more recent
data show lower levels of contamination suggesting that earlier data
may have been incorrect (CDFG, 2002). There is also evidence that white
sturgeon in the estuary accumulate selenium, but tissue concentrations
have varied over time without a trend and do not seem to be size
related (White et al., 1989). Given the available information, it is
uncertain to what extent green sturgeon are impacted by contaminants in
this DPS. Based on the fact that white sturgeon spend more time in the
estuary and green sturgeon are more marine oriented, CDFG suggests that
green sturgeon are probably less vulnerable than white sturgeon to the
effects of contaminant bioaccumulation in the San Francisco Bay estuary
(CDFG, 2002).
Concerns were raised in the status review that summer temperatures
in the Sacramento River were near the lethal limits for larval green
sturgeon; however, there is no direct evidence that elevated
temperatures are adversely affecting spawning and larval development.
In the Sacramento River, green sturgeon are thought to spawn in the
spring and summer primarily from Hamilton City to as far upstream as
perhaps Keswick Dam (NMFS, 2002; CDFG, 2002). Re-operation of RBDD in
the early 1990s to improve upstream passage for winter-run chinook is
also thought to have provided a substantial increase in green sturgeon
spawning habitat above the facility (CDFG, 2002). Spawning of green
sturgeon in the upper Sacramento River above the RBDD is supported by
the annual collection of juvenile green sturgeon in fish trapping
operations at the RBDD (1995-2001) and the Glenn-Colusa Irrigation
District (1986-2001) between the months of May and August (see Figures
13 and 14 in NMFS 2002). Since the early 1990s, significant efforts and
measures have been implemented by the Bureau of Reclamation and NMFS to
control water temperatures in the upper Sacramento River between the
RBDD and Keswick dam in the late spring and early summer so that
winter-run chinook salmon can successfully reproduce there. Under the
current protocols, water temperatures upstream from RBDD are generally
controlled by releases from Shasta and Keswick Dams so that they do not
exceed 56 degrees Farenheit (or 13.3 degrees Centigrade) from mid April
through the end of September. This period of temperature control
appears to coincide with green sturgeon spawning, egg incubation, and
larval development in the upper river, and therefore, the temperature
control efforts for winter-run chinook are likely to benefit and
protect green sturgeon as well. Temperatures cannot be controlled
downstream of RBDD or in the Sacramento-San Joaquin Delta, so elevated
temperatures could potentially
[[Page 4441]]
affect green sturgeon larval development in those areas.
Harvest impacts on green sturgeon in this DPS, at least from
fisheries in California, are thought to be minimal. Commercial fishing
for green sturgeon (and white sturgeon) has been prohibited in
California since the early 1900s. Direct recreational harvest does
occur, primarily in San Pablo Bay, but the total harvest is thought to
be very small (CDFG 2002). In addition, green sturgeon are protected by
slot limits, very restrictive take limits, and a seasonal closure in
central San Francisco Bay during the herring spawning season (January
through March). Based on tagging studies conducted by CDFG, green
sturgeon tagged in San Pablo Bay undertake extensive ocean migrations
and are recaptured in commercial and recreational fisheries in both
Oregon and Washington (CDFG, 2002; NMFS, 2002). Although there are
harvest bycatch data for green sturgeon in these fisheries, it is not
possible with the available information to directly assess the impact
on green sturgeon in the southern DPS. In order to assess direct
harvest impacts on this DPS, information is needed on the actual number
of fish taken in these fisheries that originate from the Sacramento
River spawning population as well as good estimates of the size of the
Sacramento River population. These data are not currently available.
Although direct harvest impacts on this DPS from the fisheries in
Oregon and Washington cannot be determined at this time, the available
harvest information for these fisheries suggests that overall harvest
and, therefore, harvest impacts to green sturgeon have declined
steadily since the mid 1980s.
Conclusion: There is no evidence from the available San Pablo Bay
population information that green sturgeon abundance in the southern
DPS is declining. Nevertheless, NMFS' BRT was uncertain about the
status of green sturgeon in this DPS because the method of deriving
population estimates involves numerous assumptions and there are no
direct measures of population abundance. For these reasons, the BRT
believes it is essential that immediate efforts be undertaken to
implement population monitoring for this DPS using methods that
directly assess population status. There is a great deal of uncertainty
regarding the effects of potential risk factors on green sturgeon in
this DPS. While there is some information on harvest bycatch impacts,
it appears most of the identified risk factors are not well documented
or are only suspected to be risk factors. Examples of the latter
include entrainment at the Delta water export facilities, impacts from
exotic species introductions, impacts from contaminants, and lethal
water temperatures. In the case of harvest bycatch for which there is
the most information and perhaps the greatest concern, it is not
possible to directly assess the impact of harvest on green sturgeon in
this DPS. Nevertheless, direct harvest appears to be limited in
California and harvest from fisheries in Oregon and Washington has
declined substantially since the mid 1980s and even more so since the
mid 1990s due to increasingly restrictive harvest management measures.
These harvest reductions and associated restrictive management measures
suggest that risk to green sturgeon from harvest bycatch has been
reduced. Although the risk to green sturgeon from bycatch harvest may
be declining, NMFS believes it may be prudent to consider additional
harvest protections until population monitoring information can be
obtained to assess the status of this DPS with greater certainty. Based
on a review of the best available information, NMFS concludes that the
southern green sturgeon DPS is not presently in danger of extinction
nor is it likely to become so in the foreseeable future.
Determination
The ESA defines an endangered species as any species in danger of
extinction throughout all or a significant portion of its range, and a
threatened species as any species likely to become an endangered
species within the foreseeable future throughout all or a significant
portion of its range. Section 4(b)(1) of the ESA requires that the
listing determination be 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 those efforts, if any, that
are being made to protect such species.
After reviewing the best available scientific and commercial
information for green sturgeon, NMFS concludes that the species is
comprised of two DPSs that qualify as species under the ESA: (1) a
northern coastal DPS consisting of populations in coastal watersheds
northward of, and including, the Eel River, and (2) a southern DPS
consisting of coastal or central valley populations south of the Eel
River, with the only known population in the Sacramento River.
Additional green sturgeon DPSs may be identified with further genetic
analysis and the boundaries of these two DPS may also be modified.
After assessing the risk of extinction faced by each DPS, NMFS further
determines that neither the northern or southern green sturgeon DPSs
warrant listing as threatened or endangered species at this time.
Because of uncertainties in the structure and status of the DPSs,
NMFS will add both DPSs to the agency's list of candidate species.
Additional information is expected to be collected over the next
several years and NMFS intends to reevaluate the status of green
sturgeon in five years provided sufficient new information becomes
available indicating that a status review update is warranted.
References
A list of references is available upon request (see ADDRESSES).
Authority
The authority for this section is the ESA, as amended (16 U.S.C. et
seq.).
Dated: January 23, 2003.
Rebecca Lent,
Deputy Assistant Administrator for Regulatory Programs, National Marine
Fisheries Service.
[FR Doc. 03-2034 Filed 1-28-03; 8:45 am]
BILLING CODE 3510-22-S