[Federal Register: October 9, 2002 (Volume 67, Number 196)]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
Notice of Availability of Final Stock Assessment Reports
AGENCY: Fish and Wildlife Service, Interior.
ACTION: Notice of availability of final marine mammal stock assessment
reports for Pacific walrus, polar bear, and sea otter in Alaska;
response to comments.
SUMMARY: In accordance with the Marine Mammal Protection Act (MMPA),
the Fish and Wildlife Service (FWS) has incorporated public comments
into revisions of marine mammal stock assessment reports (SARs) for
Pacific walrus, polar bear, and sea otter in Alaska. The 2002 final
SARs are now complete and available to the public.
ADDRESSES: Send requests for printed copies of the final stock
assessment reports to: Chief, U.S. Fish and Wildlife Service, Marine
Mammals Management Office, 1011 East Tudor Road, Anchorage, AK 99503,
Copies of the final stock assessment reports are available on the
Internet in Adobe Acrobat format at http://www.r7.fws.gov/mmm/SAR.
Section 117 of the MMPA (16 U.S.C. 1361-1407) requires the FWS and
the National Marine Fisheries Service (NMFS) to prepare stock
assessment reports for each marine mammal stock that occurs in waters
under the jurisdiction of the United States. Section 117 of the MMPA
also requires the FWS and the NMFS to review the stock assessment
reports: (a) At least annually for stocks that are specified as
strategic stocks; (b) at least annually for stocks for which
significant new information is available; and (c) at least once every
three years for all other stocks. If the review indicates that the
status of the stock has changed or can be more accurately determined,
the agencies are directed to revise the SARs. We published the initial
SARs in 1995 and revised SARs for Pacific walrus and polar bears in
Draft 2002 SARs were made available for a 90-day public review and
comment period on March 28, 2002 (67 FR 14959). Prior to releasing them
for public review and comment, FWS subjected the draft reports to
internal technical review and to scientific review
by the Alaska Regional Scientific Review Group (ASRG) established under
the MMPA. Following the close of the comment period, FWS revised the
stock assessments and prepared the final 2002 SARs.
Previous stock assessments covered a single stock of Pacific
walrus, two stocks of polar bears (Chukchi/Bering seas and Southern
Beaufort Sea), and a single stock of sea otters in Alaska. There are no
changes in stock identification for Pacific walrus and polar bear,
however three stocks of sea otters (southwest Alaska, southcentral
Alaska, and southeast Alaska) have now been identified.
A strategic stock is defined in the MMPA as a marine mammal stock
(A) for which the level of direct human-caused mortality exceeds the
potential biological removal level; (B) which, based on the best
available scientific information, is declining and is likely to be
listed as a threatened species under the Endangered Species Act of 1973
within the foreseeable future; or (C) which is listed as a threatened
or endangered species under the Endangered Species Act of 1973, or is
designated as depleted under the MMPA.
Only the southwest Alaska stock of sea otters was classified as
strategic. All other stocks were classified as non-strategic. Based on
the best available scientific information, sea otter numbers across
southwest Alaska are declining. In April 2000, an aerial survey of sea
otters in the Aleutian Islands indicated the population had declined by
70% during the period from 1992-2000. In August 2000 FWS designated the
northern sea otter in the Aleutian Islands as a candidate species under
the Endangered Species Act. Additional surveys in 2000 and 2001 along
the Alaska Peninsula and Kodiak archipelago also showed population
declines in these areas. As a result, the southwest Alaska stock is
classified as strategic in the final report and is under review for
possible listing under the Endangered Species Act.
A summary of the final revised stock assessment reports is
presented in Table 1. The table lists each marine mammal stock,
estimated abundance (NEST), minimum abundance estimate
(NMIN), maximum theoretical growth rate (RMAX),
recovery factor (FR), Potential Biological Removal (PBR),
annual estimated average human-caused mortality, and the status of each
Table 1.--Summary of Final Stock Assessment Reports for Pacific Walrus, Polar Bear, and Sea Otter in Alaska
Mortality causes (5 yr. average)
Species Stock NEST NMIN RMAX ER PBR ----------------------------------------------------------- Stock status
Subsistence Fishery Other
Pacific Walrus...................... Alaska................. -- -- 0.08 -- -- 5,789................. 1 4..................... Non-strategic.
Polar Bear.......................... Alaska................. -- -- 0.06 0.5 -- 45 (Alaska)........... 0 0 (Alaska)............ Non-strategic.
Chukchi/Bering Seas.... 100+ (Russia)......... -- (Russia)...........
Polar Bear.......................... Alaska................. 2,272 1,971 0.06 1.0 88 34 (Alaska)........... 0 <1 (Alaska)........... Non-strategic.
Southern Beaufort Sea.. 20 (Canada)........... 0 (Canada)............
Sea Otter........................... Southeast Alaska....... 12,632 9,266 0.20 1.0 927 301................... 0 0..................... Non-strategic.
Sea Otter........................... Southcentral Alaska.... 16,552 13,955 0.20 1.0 1,396 297................... 0 0..................... Non-strategic.
Sea Otter........................... Southwest Alaska....... 41,474 33,203 0.20 0.25 830 97.................... <1 0..................... Strategic.
Dash(--)indicates unknown value.
Comments and Responses
FWS received 4 letters containing comments for sea otters, 3
letters for Pacific walrus, and two letters for polar bears. The
comments and responses are separated below by species.
Sea Otter Stock Assessment Reports
Comment 1: One commenter noted that the calculation of
Nmin for some sea otter surveys does not incorporate
available estimates of sampling variance.
Response: We revised our approach to estimating Nmin for
surveys that are uncorrected for sea otters not detected by observers
by applying generic correction factors appropriate for the type of
survey. This approach is consistent with our finding on a recent
petition to list sea otters in Alaska as depleted under the MMPA (66 FR
55693, November 2, 2001)
Comment 2: Several commenters noted that the population estimates
for the Cook Inlet and Kenai Fiords areas are outdated, do not conform
to the established stock boundaries, and include duplication of effort
in Kachemak Bay.
Response: We have substituted recent population estimates for these
areas that remedy these problems.
Comment 3: One commenter indicated that the population estimate for
much of the southeast Alaska stock is outdated.
Response: The survey in question is 7 years old. Stock Assessment
guidelines state that abundance estimates older than 8 years are not
reliable. Although it is still acceptable for use in the current stock
assessment, we recognize the limitations of the existing data and have
requested the U.S. Geological Survey, Division of Biological Resources,
to conduct an aerial survey of sea otters in southeast Alaska. This
survey is currently underway, and will be completed in sections over
the next 2-3 years.
Comment 4: One commenter recommended that sea otter population
estimates would be clearer if they were presented in tabular form.
Response: Tables of survey results have been included in the final
stock assessment reports for sea otters.
Comment 5: Several commenters noted that sea otter population
estimates included unpublished data.
Response: Typically peer-reviewed journals follow a 1-2 year cycle
from manuscript preparation to submission to acceptance to publication.
We believe that presentation of recent unpublished survey results, from
surveys we conducted, is preferable than using older published
estimates, and more appropriately meets the standard of ``the best
scientific information available.''
Comment 6: One commenter stated that the observed sea otter
population growth rate of 12% for the Cross Sound/
Icy Strait region may not be representatives of the entire southeast
Response: We agree and have added text to clarify this point.
Comment 7: One commenter was concerned the fisheries information
does not include information about fisheries that have the potential to
interact with sea otters.
Response: Section 117(a)(4) of the Act states that stock assessment
shall ``deserve commercial fisheries that interact with the stock.'' We
interpret this to mean those fisheries for which we have information
about interactions, not fisheries with the potential for interaction as
suggested above. We see little value in speculating as to which
fisheries might interact with sea otters. For a detailed list of
fisheries and marine mammal interactions, the reader is directed to
NMFS Continuing List of Fisheries [67 FR 2410, January 17, 2002]. The
FWS relies on NMFS to provide us with estimates of fishery
interactions. For further details on the limitations of these data, the
reader is directed to the most recent NMFS Notice of Availability of
Final Stock Assessment Reports [67 FR 10671, March 8, 2002].
Comment 8: Several commenters noted harvest estimates from the
marine mammal Marking, Tagging, and Reporting Program may be biased low
to an unknown degree due to incomplete hunter compliance.
Response: We believe this potential source of bias is extremely
small for the following reason. Sea otters are hunted for their pelts,
which must be tanned before they can be fashioned into handicrafts, and
commercial tanneries will not accept untagged pelts. For accuracy, we
have inserted the word ``Estimated'' into figure legends for
Comment 9: One commenter noted that information about the number of
sea otters captured and released for scientific research was not
Response: Statistics on capture and release for scientific research
have been included.
Pacific Walrus Stock Assessment Report
Comment 10: One commenter noted that the section ``Current and
maximum net productivity rates'' referred to a study by University of
Alaska researchers to investigate the reproductive rates of free-
ranging walrus herds. The commenter recommended that the reproductive
rates and/or juvenile survival rates observed in these studies be
reported in the SAR.
Response: The FWS has concluded that these data are too preliminary
for inclusion in the 2001 SAR and has removed all references to this
study. The FWS will reconsider including this information in future
SAR's once the study is complete.
Comment 11: Two commenters recommended making changes to the
section ``Conservation issues and habitat concerns'' in reference to
the issue of global warming and its potential impacts to the Pacific
Response: At the present time there are no data available to make
reliable predictions of the net impacts that changing climate
conditions might have on the status and trend of the Pacific walrus
population. The text of the SAR has been modified to clarify this
Comment 12: One commenter noted that the SAR underestimated struck-
and-lost rates for subsistence-harvested animals and questioned the
accuracy of the sex-ratio reported for the walrus harvest in Alaska.
The commenter refers to recent FWS harvest monitoring field reports,
describing harvest monitoring activities in the Bering Strait region,
that suggest that self-reporting of struck-and-lost rates are likely to
be negatively biased and describe a harvest with a skewed sex-ratio
favoring females and dependent calves.
Response: Due to potentially negative bias associated with self-
reporting of struck-and-lost rates, the FWS did not include this data
in the SAR. The struck-and-lost estimate reported in the SAR is based
on a published study describing the number of walrus struck and lost
during monitored subsistence hunts in Alaska (Fay et al. 1994), The
annual field reports referred to by the commenter describe a subset of
the annual subsistence walrus harvest in Alaska. Although the spring
hunt in these Bering Strait communities is frequently characterized by
a sex-ratio skewed towards females, the sex ratio of the state-wide
harvest over the 5-year period described in the 2001 SAR (1996-2000)
was near parity. The source of the sex-ratio information was the FWS
Marking, Tagging, and Reporting Program, which is a State-wide, year-
round program that requires subsistence hunters to report the age and
gender of all harvested walrus to the FWS. The source of the sex-ratio
information was referenced in the text for clarity.
Comment 13: One commenter noted that the 42% struck-and-lost rate
described in the SAR was based on data at least eight years old and
speculated that this rate may change over time due to changes in
hunting conditions and practices. The commenter recommended that this
assumption should be verified from time to time and modified
accordingly if it is found to change.
Response: In the absence of more recent scientific data, the FWS
has chosen to use the published 42% rate for struck-and-lost animals as
the best available scientific information for calculation of total
harvest levels. However, the FWS agrees with the commenter that it is
important to update or verify this struck-and-lost information
periodically. The FWS hopes to initiate cooperative studies with the
Eskimo Walrus Commission to examine struck-and-lost rates in the near
Comment 14: One commenter recommended that the draft stock
assessment should emphasize that the Pacific walrus population may be
in decline, even as the subsistence hunt continues to take a very large
number of animals.
Response: The current size and trend of the Pacific walrus
population is unknown. In the absence of new survey information, it is
not possible to make reliable predictions regarding population trend.
Comment 15: One commenter noted that Russian officials consider the
level of fisheries interaction to the small. The commenter felt this
statement could be reassuring or misleading and recommended that the
statement that the level of take in Russian waters is undetermined.
Response: We agree and have changed the text in the SAR to indicate
that there are no data available concerning the incidental catch of
walrus in fisheries operating in Russian waters.
Comment 16: One commenter noted that the section on ``Fisheries
information'' refers to trawl and longline fishery interactions, but
does not distinguish the level of takes between two gear types or the
multiple fisheries that they represent.
Response: The text was modified to clarify that the only fishery
for which incidental kill or injury was reported was the domestic
Bering Sea groundfish trawl fishery. For additional information
regarding fisheries interactions, the SAR references a complete list of
fisheries and marine mammal interactions published annually by NMFS [67
FR 2410, January 17, 2002].
Comment 17: One commenter noted that the observer coverage for
fisheries observer data was not stated.
Response: The range of observer coverage over the 5-year period
(1996-2000), as well as the annual observed and estimated mortalities,
are included in Table 2 of the SAR.
Comment 18: One commenter noted that the SAR states that most of
the interactions involve walruses dead from other causes and
recommended that the report provide information to support this
Response: The text was modified to clarify that most of the
observed interactions were with decomposed walrus carcasses or skeleton
remains suggesting that the animals died prior to their interaction
with the fishing gear.
Comment 19: One commenter noted that the SAR states that the rate
of mortality and injury is estimated at ``less than two animal [sic]
per year,'' but the basis of that estimate is not clear from the data
Response: The SAR identifies the NMFS observer program as the
source of information regarding fisheries interactions in U.S. waters.
The range of observer coverage over the 5-year period (1996-2000), as
well as the annual observed and estimated mortalities are included in
Comment 20: One commenter recommended that the SAR should identify
the potential indirect impacts that bottom trawling may have on the
Pacific walrus population through alteration of habitat.
Response; Section 117(a)(4) of the Marine Mammal Protection Act
states that stock assessments shall ``describe commercial fisheries
that interact with the stock.'' We interpret this to mean those
fisheries for which we have information about direct interactions with
walrus, not fisheries with potential secondary impacts as suggested
Polar Bear Stock Assessment Reports
Comment 21: One commenter questioned whether the process of
delineating stocks is based on political reasons such as management
agreements or evidence of significant biological distinction.
Response: We clarified the stock assessments for the Chukchi/Bering
Seas stock and the Southern Beaufort Sea stock assessment to indicate
that past and present management regimes have consistently
distinguished between the Southern Beaufort Sea and Chukchi/Bering Seas
stocks based upon biological evidence presented in the stock
Comment 22: Two commenters noted that the evidence suggesting that
the stock has grown since 1972 was not sufficient to support the claims
made regarding the trends in this population. This section also states
that it is realistic to infer that the Chukchi/Bering Seas stock
mimicked the growth pattern and later stability of the Beaufort Seas
stock since that stocks have experienced similar management and harvest
histories. However, this inference could be reasonably questioned for
several reasons. First, growth patterns are a function of multiple
factors including, but not limited to, harvest and management
histories. As harvest and management histories are not the only
determinants of growth trends, and as other possible factors (e.g.,
disease, shifts in distribution or availability of prey) are not
evaluated, this inference should be questioned.
Response: We agree that scientific evidence is scant regarding
population trends for the Chukchi/Bering Seas stock. Most of the
evidence cited in sub-points a-e are from previous data should have not
been reaffirmed in recent years. We have revised this section to
indicate that, while evidence or impressions of population growth were
appropriate previously, current data to support this conclusion is not
available. For reasons stated earlier, it appeared reasonable to
believe that the Chukchi/Bering Seas stock experienced growth following
a 50% reduction in harvest in the 1970's and that population growth
likely continued up to the early 1990s, similar to the Beaufort Sea
stock. The Beaufort Sea stock stabilized in the 1990's. It is possible
that the same may have been true for the Chukchi/Bering Seas stock,
although this population was subject to additive unknown harvest
levels, starting around 1992, that may have affected its status.
Supporting evidence is not available to confirm the status of the
population, and recent information regarding increased Russian harvest
and decreased Alaska harvest are cause for concern. Consequently, we
have chosen to designate the status of the Chukchi/Bering Seas stock as
Comment 23: One commenter noted that the harvest patterns for the
two stocks may not have been the same. Subsistence harvests are
illustrated in Figure 2 of each SAR, but comparisons should be done
carefully as the y-axis is not the same in the two figures, and it
appears that the number of bears taken from the Chukchi/Bering Seas
stock may have been on the order of two times the number taken from the
Southern Beaufort Sea stock. The significance of that difference will
depend in part on the respective size of the two populations, and since
the size of the Chukchi/Bering Seas stock is undetermined, the effects
of harvesting are not clear.
Response: Figure 2 illustrates that the trend of declining U.S.
harvests, post MMPA, were similar for both stocks. We acknowledge that
the respective size of the two populations is crucial to understanding
the effect of any harvest regime. Recent decline in harvest levels from
the Alaska Chukchi/Bering Seas during the period 1996-2001 and reports
of substantial illegal harvest in Russia are of concern. Because of
these concerns, we revised the status of this stock to unknown.
Comment 24: One commenter noted that the report does not provide a
basis for confidence in the precision and reliability of harvest
estimates for Russian harvests.
Response: We have changed the Figure 2 caption to ``Annual Alaska
polar bear harvest from 1961-2001.'' We have added text in the SAR to
clarify that harvest estimates for Chukotka are based on anecdotal
Comment 25: Two commenters suggested that data for this stock
continue to be insufficient for establishing a population estimate and
urge the FWS to prioritize its research needs to improve the data
available on this stock.
Response: The FWS has placed an emphasis on the development of the
US/Russia Bilateral Treaty for the conservation of this population
stock. The bilateral treaty includes provisions for conducting research
to monitor population trends and develop population estimates for the
Chukchi/Bering Seas stock. The current polar bear research program does
not have adequate personnel or funding to conduct operations in both
the Southern Beaufort Sea and the Chukchi/Bering Seas. The FWS
continues to support implementation of the Bilateral Treaty, unified
harvest management programs in Russia and Alaska, and conducting an
aggressive polar bear research program to more effectively monitor this
Comment 26: One commenter noted that factors which may affect
growth rates, including potential effects of global climate change and
persistent organic pollutants were not included in the Southern
Beaufort Sea stock assessment.
Response: We have incorporated these references into the Southern
Beaufort Sea stock assessment.
Comment 27: One commenter recommended including the basis for the
statement that the number of unreported kills since 1980 to the present
time is thought to be negligible.
Response: We consider the number of unreported kills since 1980 to
be negligible for the following reasons. All harvested bears in Alaska
are required to have the skull and skin tagged through FWS's Marking,
Reporting Program. Due to the relatively small number of bears taken;
the high visibility, cultural importance, and sharing of the take
within villages; the relatively large size and visible methods of
handling polar bear hides; and repeated visits by biologists and
reports from harvest monitors, we believe that the total harvest is
accurately represented by the tagged and untagged bear harvest totals.
Comment 28: One commenter requested clarification on whether
illegal hunting in Russia increased or became significant in 1992, and
whether the occurrence of illegal hunting has been acknowledged since
Response: The text has been clarified to indicate that the
occurrence and significance of illegal hunting was thought to have
begun in 1992.
Comment 29: Two commenters noted that the basis for the statement
that the ``stock appears to be stable despite a substantial annual
harvest'' should be either justified with suitable evidence or deleted.
Response: For reasons previously stated, we have modified the text
to acknowledge that the population status or trend of this population
Comment 30: The draft stock assessment does not consider the impact
of oil and gas development on polar bears as is done with the sea otter
Response: Oil and gas exploration or development projects have not
been proposed in the Alaska Chukchi/Bering Seas during the past five
years. If future oil and gas development projects are proposed, we will
consider the potential effects to polar bears.
Southern Beaufort Sea
Comment 31: One commenter noted that it was not clear if estimates
of the female, total, and minimum populations pertain to the entire
period from 1986 to 1998, or perhaps only to the end of the period.
Previous estimates by the same lead author suggested a doubling of size
during the period from 1988 to 1998, although the report later suggests
that the population is stable.
Response: We have condensed and clarified this information to
indicate that Amstrup (unpublished data) estimated the total population
to be 2,272. This population estimate for the period 1986-98 was based
on an estimate of 1,250 females (CV = 0.17) and a sex ratio of 55%
female from the best model (Amstrup et al. 2001). Nmin is
1,973 bears for a population size of 2,272 anc CV of 0.17.
Comment 32: In addition, it was not clear that the estimate of the
minimum population is calculated correctly. The female population is
estimated as 1,250 with a CV of 0.17. The total population is estimated
by 1,250/0.55 and, based on the estimated minimum population, it
appears that 0.55 was treated as a constant. Presumably, however, 0.55
is a correction factor that is also estimated with some degree of
error, and that error should be included in the calculation of the CV
for the total population estimate.
Response: A variance was not calculated for the 55% female sex
composition and thus the ration is used as a constant for the abundance
estimate. The Nmin estimate is correct, and typographic
errors in the formula have been corrected.
Comment 33: One commenter suggested that the basis for the
arguments that the population may have approached carrying capacity (K)
was not evident based on the information provided. The report states
that ``the indication that the population was stable, births
approximated deaths, is noteworthy.'' It is unlikely that the data are
available to confirm that births approximated deaths, so that statement
appears to be a supposition. It is not clear what is meant by the
statement that this supposition seems ``noteworthy.'' Clarification
would be useful.
Response: The text has been revised to emphasize that the most
recent population modeling exercise (Amstrup et al. 2001) suggests that
the population grew during the late 1970's and 1980's and stablized in
the 1990's. Inferences to the population relationship with carrying
capacity have been removed. The statement that modeling indicates that
the population stablized in the 1990's (Amstrup et al. 2001) is
supported and has been retained as noteworthy since it indicates a
change in status.
Comment 34: One commenter suggested that, without good juvenile
survival estimates, life-history analysis and estimated growth rates
may be inaccurate.
Response: Juvenile survival rates are not known for this
population, nor well known for any polar bear population. We have good
information on survival estimates of yearlings and two-year-old bears.
Recently weaned two-year-old bears were assigned survival estimates of
the two-year-old bears, and the three-year-old bears were given
survival estimates of yearlings. We believe that these estimates are
Comment 35: The stock assessment for the Southern Beaufort Sea
stock of polar bears notes that the potential biological removal level
for this stock has been adjusted upward from 59 to 88 to account for
the male harvest bias. For this stock, such an adjustment may be
consistent with the purpose of PBR as set forth in the first sentence
of the statutory definition (section 3 (20)), but is not consistent
with the second part of the definition setting forth the formula for
Response: In the narrative, PBR levels are calculated with and
without a sex-biased harvest adjustment. We have chosen the adjusted
PBR since it more accurately reflects what we would consider as a safe
biological removal level. This is an issue of perception more than
substance, since there is no application beyond taking of polar bears
incidental to commercial fishing, and no incidental take of polar bears
by commercial fisheries has occurred.
Comment 36: One found that the reported numbers of polar bear kills
in the section on ``Sport and native Subsistence Harvest'' was
confusing. A table of annual bear harvests by stock, time period,
country, and type of hunt (sport versus subsistence) would help to
clarify the history of harvest from this stock.
Response: We have reorganized and revised the text in this section
and Figure 2 caption to clarify the harvest information. Figure 2 is
included to illustrate a decline in the Alaska harvest after passage of
the MMPA in 1972. The last five years of the Canada harvest data for
the Southern Beaufort Sea stock have been summarized in the text.
Comment 37: One commenter noted that it was unclear as to whether
the reference to industry pertains to the oil and gas industry
specifically or all industry in general.
Response: The use of industry in the generic sense is correct in
this sentence. While the incidental take regulations apply to the oil
and gas industry, the statute allows U.S. citizens, including any
industry, to petition for the development of incidental take
Amstrup, S.C., T.L. McDonald, and I. Stirling. 2001. Polar bears in the
Beaufort sea: A 30-year mark-recapture case history. Journal of
Agricultural, Biological and Environmental Statistics. Vol 6(2):221-
Fay, F.H. J.J. Burns, S.W. Stoker, and J.S. Grundy. 1984. The struck-
and-lost factor in Alaskan walrus harvests. Arctic 47(4):368-373.
Dated: August 29, 2002.
David B. Allen,
[FR Doc. 02-25679 Filed 10-8-02; 8:45 am]
BILLING CODE 4310-55-M