Alaska Fisheries Science Center National Marine Mammal Laboratory Report for April-May-June 1998 Quarterly Report

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 year’s 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 Dall’s porpoise. The complete killer whale dive record during the pursuit and capture of the Dall’s 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 NMML’s 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 Dall’s porpoise, 8 killer whales, 22 humpback whales, 19 fin whales, 1 Cuvier’s 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 NMML’s 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 IWC’s 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 Dall’s 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 year’s 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 year’s 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.