(Quarterly Report for Oct-Nov-Dec 1998)
Beluga Whales in
Cook Inlet, Alaska
Five stocks of beluga whale (Delphinapterus leucas) occur in Alaska waters, the most isolated of which is the small population in Cook Inlet, near Anchorage. All Alaska beluga stocks are hunted to some degree by Alaska Native subsistence hunters, and there may be some incidental take in coastal fisheries. The latest calculations indicate there are approximately 347 (N best) beluga whales remaining in Cook Inlet from a population that may have numbered near 1,000 whales 20 years ago. Though documentation of subsistence harvest is difficult, it appears that somewhere between 40-70 whales have been removed from this population annually in recent years. The geographic and genetic isolation of the Cook Inlet stock in combination with the stocks site fidelity make the stock especially vulnerable to extirpation as a result of such large, persistent harvests.
The Cook Inlet stock of beluga whales has become a critical management concern. NMFS recommended a potential biological removal (PBR) for this stock of only three whales per year in the 1999 draft Stock Assessment Report and on 19 November 1998 initiated a formal comprehensive status review for the stock [Federal Register Vol. 63, No. 223] to determine whether it is warranted to designate the stock as depleted under the Marine Mammal Protection Act (MMPA) or to list it as threatened under the Endangered Species Act (ESA). The NMFS will undertake the review in conjunction with two Alaska Native Organizations (ANOs), the Alaska Beluga Whaling Committee (ABWC) and the Cook Inlet Marine Mammal Council (CIMMC).
The Cook Inlet stock of beluga
whales has been monitored since 1993 by the National Marine Mammal Laboratory (NMML), in
cooperation with the NMFS Alaska Regional Office (ARO), the ABWC, and the CIMMC.
Research activities have focused on annual aerial surveys (1993-98) to determine
whale distribution and estimate population size, and tagging studies (1994-95) to gauge
whale movements and dive profiles. Results of this research suggest that the
population is decreasing in size, with summertime distribution increasingly confined to
the northern portion of upper Cook Inlet (Figure 1 above). Furthermore, aerial
counts of beluga whales were lower in 1998 (193) than in the last 5 years (260-360).
Although some of this apparent decline could be due to observer performance,
variability is likely minimized by consistency of survey season (June/July), methods, and
personnel among years.
NMFS will hold a status review meeting in Anchorage on 8-9 March 1999 where research results and public comments will be considered to evaluate the current status of the Cook Inlet beluga stock. Beluga distribution, abundance and trends, reproduction capacity, food habits, and biological and health parameters will be addressed. The effects of subsistence harvest, the potential effects of other anthropogenic activities, and beluga natural mortality will also be discussed. Meanwhile, NMML is preparing for another season of aerial surveys and satellite tagging studies currently scheduled for May-June 1999. All status review and research activities will continue to be coordinated with the ARO, ABWC, and CIMMC to encourage the best possible management of this small isolated population of beluga whales.
By Sue Moore.
Census of Northern Fur Seals on the Pribilof Islands
The NMMLs Alaska Ecosystem Program conducted censuses of northern fur seal adult males and pups on the Pribilof Islands of St. George and St. Paul in July and August 1998. Census surveys of the northern fur seal population in the Pribilof Islands has been conducted since the early 1900s. Adult males are counted annually from cliffs and catwalks during the peak of the breeding season in July. Numbers of pups are estimated every other year using mark-resighting methods. Pups are marked in early August when they are about 1 month old. On St. George Island, estimates are obtained on all rookeries and on St. Paul Island, on a sample of about half the rookeries. The mark is made by shearing a small patch of hair from the heads of several thousand pups; the shearing removes black hair on the surface and exposes white underfur making a highly visible mark. Later, biologists visit the rookeries and count numbers of marked and unmarked animals in samples of groups of pups. The total number of animals on each rookery is estimated from the known number of marked animals and the proportion of marked animals in the samples. Biologists also traverse the sites and count the number of dead pups. These counts, together with the mark-resighting estimates, provide an estimate of the total number of pups born for each rookery. If all rookeries are sampled, estimates for the island are obtained by summing the rookery totals; if pup estimates are available from only a subsample of rookeries, estimates are obtained by multiplying the total on sampled rookeries by a correction factor equal to the total number of harem bulls on the island divided by the number of harem bulls on the sample rookeries.
The estimated number of fur seal pups has hovered around 180,000 on St. Paul Island since the early 1980s and about 22,000 on St. George Island since the late 1980s (Figure 2 above).
The 1996 and 1998 estimates for St. Paul Island are not significantly different from 180,000 (Table 1 above). On both islands, the numbers of pups decreased from unknown causes in the mid-1970s. On both islands, the current mortality rates are similar to those observed during the past 15 years - they have ranged between 2% and 6% since the early 1980s (Table 1 above).
Numbers of adult males tend to fluctuate more than numbers of pups (Figure 3 above) and data collected during the past 4 years (Table 2 below) are consistent with that pattern. Although the number of harem bulls appears to have decreased somewhat over the past 4 years, this change is not statistically significant (P = 0.6).
By Anne York.
Pinniped Predation on Endangered Salmonids
Members of NMMLs California Current Ecosystems Program conducted field research between March and October 1998 on pinniped predation on certain runs of Pacific salmon listed under the Endangered Species Act (ESA). Pinniped food habits investigations have been conducted to assess the diet of harbor seals in the Umpqua and Columbia Rivers and assess the diet of harbor seals, California sea lions, and Steller sea lions in and near the mouth of the Ozette River. The objective of these studies is to assess whether ESA-listed species occur in the diets of the respective pinnipeds.
Between March and October, 1,406 scat samples were collected from harbor seals at the Columbia River and the Umpqua River to assess the impact of harbor seal predation on endangered salmonids. Sorting the 579 samples from the Umpqua River began in mid-October and, to date, 90% (529) of the samples have been sorted. Identification of otoliths and bones to species will begin as soon as sorting is completed.
Scats (567) were collected from harbor seals near the Ozette River from May through September. Of these, 311 have been cleaned and sorted; prey identifications from otoliths and cephalopod beaks have been made on about 225 samples. Approximately 150 sea lion scats were collected in May and June; processing and prey identification of these samples has not taken place to date.
By Bob DeLong.
Washington Gray Whales Surveyed
In September and October 1998, vessel surveys conducted in the Strait of Juan de Fuca and off the northern Washington coast resulted in the sighting of 57 gray whales. Forty-three gray whales were sighted in the Strait of Juan de Fuca and 14 along the northern Washington coast. Of the 57 sighted gray whales, 43 were photographed for later identification. Samples of skin and blubber from gray whales were collected using a biopsy dart to test the animals for organo-chlorine pollutants. Nine gray whales were biopsied in September, six in October and three in November. Four of the gray whales which were biopsied in October and November were also radio-tagged.
Aerial, vessel, and land-based surveys were conducted in November and December 1998 off northern Washington to determine the timing and distribution of the gray whale southbound migration from the Bering Sea. Five vessel and four aerial surveys were conducted off the Washington coast. Vessel surveys, ranging from 4 to 10 nautical miles off the coast, were all completed prior to 3 November and resulted in no gray whales sighted. Aerial surveys were flown in November and December along transect legs up to 30 miles offshore and resulted in the first migrant whale sightings on 23 December. Land-based surveys were conducted from Tatoosh Island at the entrance to the Strait of Juan de Fuca during 7-16 December but resulted in no sightings of migrating gray whales. These observations indicated the gray whale southbound migration in 1998 was 3-4 weeks later than expected.
By Bob Delong.
Alaska Scientific Review Group Meeting
The Alaska Scientific Review Group (SRG) met in Anchorage, Alaska, on 18-20 November 1998. The objectives of the meeting were to 1) conduct an initial review of revised 1999 Stock Assessment Reports; 2) participate in a detailed discussion of Cook Inlet beluga whales, with NMFS personnel and representatives from the Cook Inlet Marine Mammal Council, Alaska Beluga Whale Committee, Alaska Native subsistence hunters, and other interested parties; 3) review NMFS and Fish and Wildlife Service plans for marine mammal research and management; and 4) plan for joint SRG meetings in spring 1999 with the Atlantic and Pacific SRGs.
The stock assessments for 12 Alaska stocks were revised for 1999. The revised stock assessments include western U.S. Steller sea lions, eastern U.S. Steller sea lions, all five beluga whale stocks (Cook Inlet, Bristol Bay, eastern Bering Sea, eastern Chukchi Sea, and Beaufort Sea), western North Pacific humpback whales, central North Pacific humpback whales, eastern North Pacific transient killer whales, Bairds beaked whales, Stejnegers beaked whales, and Cuviers beaked whales. The draft 1999 Stock Assessment Reports for these stocks should be available for public comment in winter 1999.
By Scott Hill.