amj99 Quarterly Rpt. sidebar
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(Quarterly Report for April-May-June 1998)
Beluga
Whales In Cook Inlet
Beluga whales (Delphinapterus
leucas) living in Cook Inlet, Alaska, near Anchorage belong to a small, isolated stock
that is hunted annually by Alaskan natives. The latest calculations indicate there are
approximately 700 whales in this stock. Annual takes of 40 animals or more exceed
current estimates for sustainable harvest levels of 14 or less (as determined through
calculations of Potential Biological Removal). Accordingly, the Cook Inlet stock of
beluga whales has become a management concern, and NMFS may be required to reclassify it
under the Marine Mammal Protection Act or the Endangered Species Act.
To monitor the Cook Inlet stock, the
National Marine Mammal Laboratory (NMML), in cooperation with the Alaska Regional
Office, the Alaska Beluga Whale Committee, and the Cook Inlet Marine Mammal Council, has
made systematic aerial surveys each year from 1993 to 1998. Survey protocol has
included flights along 100% of the coastal areas, including appropriate distances up
rivers. The upper inlet, where almost all of the whales have been seen in June-July,
is surveyed three or more times each year. In addition, a sawtooth pattern of transects is
flown across the entire inlet.
This year the aerial survey project
was repeated during 9-15 June, continuing the same research protocol used in previous
years. This protocol involves the use of a high wing, twin engine aircraft (an Aero
Commander) and a team of five observers that survey at an altitude of 800 ft at a speed of
100 knots. Surveys are conducted along the entire coastline of Cook Inlet. In
addition to the coastal surveys, offshore transects are flown across the inlet where
a sawtooth pattern of tracklines is used to cross over the shoreline at points
approximately 20 miles apart, starting from Anchorage and zigzagging to the southern
limit of Cook Inlet. Three of this years observers also participated in nearly all
of the five previous surveys, thereby providing a high comparability of effort among
years. All of the coastal areas of Cook Inlet including significant rivers were
surveyed in good or excellent weather conditions except the area south of Seldovia on the
east side of the inlet and south of Kalgin Island on the west side of the inlet, where
high winds reduced visibility. This area of the southwesternmost part of Cook Inlet
has had only two sightings of beluga whales in the past 4 years.
During the June 1998 survey, no
beluga whales (except two dead ones) were found south of the Susitna Delta. The
delta, in the northwest corner of Cook Inlet, is where most whales have been seen in the
past. One large group was persistently at the mouth of the Little Susitna River or
the Big Susitna (daily median counts were 57, 69, and 109). Several groups were in
Knik Arm (north of Anchorage), similar to what we found in 1997 (daily median counts were
93, 72, and 42). The data indicate that the groups moved between the Susitna
and Knik areas (daily sums were 150, 141, and 151). Another isolated group was
in Chickaloon Bay (south of Anchorage) each time we surveyed there (daily median counts
were 23, 42, and 41), consistent with all of our previous surveys.
Summary counts were 173, 183, and
193 for the respective survey days in 1998. The highest of these summaries, 193,
came from the survey flight with the best viewing conditions. This aerial count is
well below counts using comparable methods during 1993-97, which ranged from 260 to 360.
Some of this apparent decline may be due to observer performance; the observers may
differ in how they count, and each season staff of the observer team has changed
some. Also, the higher number of beluga whales at river mouths in past years may
have led to their being undercounted. As the population declines, densities of whale
groups diminish, and observers make relatively more accurate counts. Accordingly, this
means that using the index of aerial counts from 1993 to 1998 would lead one to
underestimate the rate of decline.
The highlights from the aerial
survey of Cook Inlet 1998 were that: 1) the distribution of beluga whales appears to
continue to diminish, as no whales were found south of the Susitna Delta this year and 2)
aerial counts were lower in 1998 than in previous years.
By David Rugh.
Seventh Meeting
of the Alaska Scientific Review Group
The seventh meeting of the Alaska
Scientific Review Group (ASRG) was held at the NMFS Regional Office facility in Juneau,
Alaska, 2-4 June 1998. The purpose of the meeting included 1) final review of
revised 1998 Stock Assessment Reports (SARs) for NMFS and the U.S. Fish and Wildlife
Service, 2) review of Alaska fisheries that interact with marine mammals, and 3)
development of recommendations regarding future research and management plans for 1998 and
beyond. Meeting minutes are available from Douglas DeMaster (NMML).
The next meeting of the ASRG is
tentatively schedule for 16-20 November 1998. Because of the potentially adverse
effects of the subsistence harvest of beluga whales in Cook Inlet, the ASRG has proposed
meeting in Anchorage for its next meeting. One of the primary topics for discussion
will be the Cook Inlet beluga whale stock. The ASRG has recommended that NMFS
contact the Cook Inlet Marine Mammal Council (CIMMC) regarding the possibility of the ASRG
meeting with the CIMMC and many of the local hunters.
By Doug DeMaster.
Killer Whale
Research in Southeast Alaska
Research was conducted aboard the
NOAA ship John N. Cobb between 4 and 17 June 1998 as part of a long-term
study to collect information on the distribution, abundance, and stock structure of killer
whales (Orcinus orca) in Southeast Alaska. Population levels were
investigated through the use of photo-identification methods. Photographic data
collected from 1989 through 1996 have documented 250 killer whales in the Southeast Alaska
region. Through comparison of photographs, killer whales observed in Southeast Alaska have
also been seen as far south as California and as far north as Prince William Sound,
Alaska. Since 1994, biopsy darts have been used to provide small samples of skin. These
samples are then used by geneticists to determine the degree to which different pods of
whales from different areas are related. This study is important in the management of
killer whale mortality incidental to commercial fisheries because it provides necessary
stock identification data.
This year a new project was
initiated on Southeast Alaska killer whales with the help of Dr. Robin Baird, a
cetacean biologist from Canada who has developed a new method using suction cup-type tags
for tagging cetaceans. Two killer whales were radio-tagged with these suction cup
tags. The tags remained on the whales 10 and 12 hours, respectively.
Approximately 30 minutes after the first tag was deployed, the killer whale began
preying on a Dalls porpoise. The complete killer whale dive record
during the pursuit and capture of the Dalls porpoise was collected. Dive
profiles of killer whales in Alaska will be compared to similar dive data collected on
killer whales in Puget Sound.
By Marilyn Dahlheim.
Cetacean Aerial
Surveys in the Gulf of Alaska
Researchers from NMMLs
Cetacean Assessment and Ecology Program began line transect aerial surveys on 26 May 1998
for harbor porpoise (Phocoena phocoena) and other small cetaceans in the Gulf of
Alaska, offshore from Cape Suckling to Unimak Pass, and in Prince William Sound.
Surveys are conducted from a NOAA Corps DeHavilland Twin Otter, flown at an altitude
of 152.5 m (500 ft) and an airspeed of 185 km/hr (100 knots). The survey route
design differs slightly by area. Four sets of sawtooth lines covered the offshore
waters from Cape Suckling to Unimak Pass, along the south and east sides of Kodiak Island.
Each line consisted of two strata, the first (short sawtooth) extending 15 nmi
seaward, or to the 50 fathom line, whichever was farthest from shore. The second
strata (long sawtooth) extended to the 1,000 fathom line. A similar pattern of
transect legs is planned for Shelikof Strait, following a zigzag pattern between the
Alaska Peninsula and Kodiak Island. Larger inlets and bays will also be included in
the survey. The survey in Prince William Sound consisted of two lines: one covering
the central waters and one along the coast with extensions into selected inlets.
As of this writing, the surveys have
been completed for most areas in the eastern Gulf of Alaska, including Prince William
Sound. A total of 33.4 survey hours had been flown as of 9 July, with sightings of
39 harbor porpoise, 46 Dalls porpoise, 8 killer whales, 22 humpback whales, 19
fin whales, 1 Cuviers beaked whale, 8 unidentified dolphins, 10 unidentified whales,
14 harbor seals, 16 Steller sea lions, and 3 unidentified pinnipeds. Once the 3 years of
surveys are completed, the data will be used to estimate annual abundance, which is one of
the key information needs necessary to manage marine mammal-fishery interactions, as
required under the Marine Mammal Protection Act.
By Rich Ferrero.
Ice-Associated
Harbor Seal Capture Techniques
The NMML develops correction factors
to account for harbor seals not present or visible when aerial census surveys are
conducted during August molt-season surveys. Previous correction factors have been
developed for seals hauling out on rocky and sandy substrates in Alaska, but little is
known about the haulout patterns of harbor seals which utilize ice floes from calving
glaciers, primarily because no one has been able to capture them. Last year in Aialik
Glacier, near Seward, members of NMMLs Polar Ecosystem Program experimented with a
variety of net types and capture techniques to successfully capture ice-associated
harbor seals. We successfully captured four seals, two pups of the year, one
yearling, and one adult. Two seals were males and two were females. The seals
were weighed and measured and had blood drawn (for condition studies with University of
Alaska Fairbanks), genetics samples taken (for stock identification studies with the
Southwest Fisheries Science Center), and standard flipper and VHF radio tags attached.
During winter 1998, the capture nets were redesigned, modifying color, mesh size,
material, lead and cork-lines, and net length and depth.
From 20-30 May 1998, NMML scientists
in collaboration with the ADF&G traveled on the John N. Cobb to the Sawyer
Glacier (Tracy Arm), Dawes Glacier (Endicott Arm), and La Conte Glacier in Southeast
Alaska to experiment with the effectiveness of the new capture nets and various deployment
and capture techniques (active and passive). Ten seals were successfully captured in
4 days including both sexes and all age categories. As in the 1997 studies, the
seals were weighed, measured, and sampled for blood (for condition studies with
scientists from the University of Alaska Fairbanks) and genetic material (for stock
identification studies with scientists from the Southwest Fisheries Science Center), and
standard flipper and VHF radio tags were attached. Tagged seals are monitored by
aircraft and remote data collection computers to develop the correction factors. The
redesigned nets and capture techniques were successful, and the NMML team is preparing for
capture operations in August 1998 in Aialik Glacier where it hopes to capture and
instrument 25-35 seals.
By Dave Withrow.
1998
International Whaling Commission Meeting
The annual meeting of the
International Whaling Commission (IWC) was held this year in Muscat, Oman, from 27 April
to 9 May. Each year the NMML summarizes its research on cetaceans, including field
research, analyses and development of techniques, biopsy,sightings, photo-identification
and telemetry data, stock assessment, and other relevant studies for incorporation with
other Science Center reports in a U.S. progress report on cetacean research to the
International Whaling Commission (IWC). The NMML annually provides management advice
through the IWCs Scientific Committee (SC) on North Pacific gray whales, humpback
whales, and bowhead whales, and provides information on the status of small cetaceans,
such as beluga whales, harbor porpoise, and killer whales.
This year the NMML reported on
shore-census of gray whales in California; photo-identification surveys of gray whales in
Washington state waters; a harbor porpoise aerial survey of the coastal waters of Oregon,
Washington, and southern British Columbia; continued work on a North Pacific humpback
photo-identification collection of over 24,000 photographs; and development of a telemetry
tag for deployment on Dalls porpoise. Cynthia Tynan (University of Washington) and
NMML Director Douglas DeMaster prepared a paper titled Ozone depletion in the
Arctic for presentation at the meeting. Tynan also submitted the paper
Critical habitat and abundance estimation of right whales in the southeast Bering
Sea. Other scientific documents coauthored by NMML scientists and submitted to the
IWC were Update on The North Pacific Humpback Whale Fluke Photograph
Collection by Sally Mizroch, and S.A.D. Harkness; A Bayesian assessment
of the Bering-Chukchi-Beaufort Seas stock of bowhead whales using Bayesian and Full
Pooling Bayesian synthesis methods by Jeff Breiwick; Sensitivity of the
assessment of the Bering-Chukchi-Beaufort Seas stock of bowhead whale (Balaena
mysticetus) to alternative assumptions by Paul Wade (detailed to NMML from
Office of Protected Resources); and Potential limits to anthropogenic mortality for
harbour porpoises in the Baltic region by Berggren, P., P.R. Wade, J.
Carlstrom, and A.J. Read.
Last year, catch limits for several
whale stocks subject to aboriginal subsistence whaling activity were agreed by the IWC.
For the Bering-Chukchi-Beaufort seas stock of bowhead whales, taken by Alaskan Eskimos and
native peoples of Chukotka, the total number of landed whales for the years 1998 - 2002
shall not exceed 280 whales, with no more than 67 whales struck in any year (up to 15
unused strikes may be carried over each year). For the eastern North Pacific gray whales,
taken by those whose traditional, aboriginal and subsistence needs have been
recognized, a total catch of 620 whales is allowed for the years 1998-2002 with a
maximum of 140 in any one year. Other aboriginal catch limits were set for west
Greenland fin and minke whales, east Greenland minke whales, and humpback whales.
A major assessment of the
Bering-Chukchi-Beaufort seas stock of bowhead whales was also conducted at this
years meeting. In 1997 it was agreed by the SC that the most appropriate
methodology for assessing this stock was a standard Bayesian analysis. Debate has
occurred regarding the merits of two standard Bayesian analysis methods. One, the
forward method, puts a prior distribution on K, the carrying capacity, and the
population model is projected forward to the current year. The other, the
backward method, puts a prior value on the current abundance and computes a K
that gives a trajectory resulting in the current abundance. An alternative Bayesian
analysis was also developed, in which multiple prior distributions are geometrically
pooled. The best estimates of replacement yield (RY) from agreed assessments using a
backward method and pooling of prior values ranged from 184 to 210. As in the last IWC
bowhead assessment, a conservative approach using the lower 5th percentile of
the posterior distribution of RY was used to provide management advice. These lower
bounds on RY (5th percentiles) were 108 (full pooling) and 123 (backward
method), well above the 1997 kill of 62 (known kill = 48; estimated struck and loss
= 14).
There has been a major research
effort since 1978 by NMFS and North Slope Borough scientists aimed at estimating current
abundance and rate of increase for the Bering-Chuckchi-Beaufort seas stock.
Abundance estimates made in the late 1970s suggested a population size of about
2,000 animals, while the current estimate, based on empirical Bayes methodology, is 8,200
with a 95% confidence interval from 7,200 to 9,400. The annual rate of increase of
the population from 1978 to 1993 is estimated at 3.2% with a 95% confidence interval of
1.4% to 5.1%. The current population size and rate of increase are now known with
greater precision for bowhead whales than for any other stock of large whales, except the
eastern North Pacific gray whale. The latter have been studied by NMML since the mid
1960s, resulting in precise estimates of abundance and a rate of increase.
At this years meeting, the
Commission approved the establishment of a new scientific journal which will commence in
early 1999: International Journal of Cetacean Research and Management.
By Jeffrey Breiwick.
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