Report for Jan-Feb-Mar 2000)
Sea Lion Research in the Aleutian Islands and Gulf
Scientists from the National Marine Fisheries Service’s Alaska Fisheries Science Center, Colorado State University, and the University of Alaska Sea Grant Program conducted Steller sea lion research in the Aleutian Islands region and Gulf of Alaska aboard the U.S. Fish and Wildlife Service vessel Tila from 24 February through 15 March 2000. The primary goal of this cruise was to capture juvenile and pup sea lions for collection of blood and other biological samples and for deployment of satellite-linked time-depth recorders. A secondary goal was to go ashore at any accessible haul-out site to collect sea lion scats (fecal material) for food habits analyses. Capture effort was concentrated in three geographical regions: Seguam Island, the Krenitzen Islands and Unimak Pass, and eastern Kodiak.
The scientific party boarded the Tila at Adak, Alaska, on 24 February. Most of the cruise was conducted under storm- or gale-warning flags, as a succession of low-pressure weather systems swept across the region, delivering high winds and heavy seas. Several of our intended research sites were fully exposed to weather (e.g., southwest winds and seas washing directly onto Lake Point, Adak). Other sites may have been on the leeward sides of islands, but the lack of protection from surging waves made them unworkable on most days (e.g., Seguam, Yunaska, and Jude Islands). Consequently, we spent much of our time at anchor in shelter when conditions precluded safe landings at haul-out sites, striving to be in position to go ashore and work when the weather did let up. This strategy resulted in a very successful day of work at Turf Point, Sequam Island. Even in the relative protection of the Krenitzen Islands, we constantly changed anchorages and target haul-out sites in reaction to changes in wind direction and speed. When we were able to land at haul-out sites in the Krenitzen Islands, wind direction frequently was exactly wrong for stalking sea lions. On several occasions, all animals spooked and departed from the haulout before a capture could be attempted. We were unable to get ashore at haul-out sites along the eastern coastline of Kodiak Island (Twoheaded Island, Cape Barnabas, Gull Point, Cape Chiniak) because of easterly winds and seas, but we did have one workable day at Long Island near Kodiak City and one day in the northern Archipelago (Sea Otter Island and Latax Rocks). A severe storm warning caused us to curtail our work a day early. We concluded the cruise at Homer, Alaska, on 15 March.
During the Tila cruise, we visited 29 Steller sea lion rookery and haul-out sites from Lake Point, on Adak Island in the central Aleutian Islands region, to Flat Island in lower Cook Inlet. We made no attempt to land at 19 of these sites, either because conditions prohibited safe landing or there were so few animals hauled out that the low likelihood of successful results did not warrant disturbance. We successfully landed ashore at nine different sites. On one occasion we went ashore but were unable to reach the haul-out site (Silak Island in Little Tanaga Strait). We collected a total of 219 scats from ten shore visits to nine different sites: 13 scats from Seguam, 174 scats from the Krenitzen Islands (five sites), and 32 scats from the northern Kodiak Archipelago (three sites).
We captured nine pup and yearling sea lions: five at Seguam Island (Turf Point: four females, one male), two at Aiktak Island (one female, one male), and two at Long Island (two males). Mean mass was 82.2 kg (SD=14.3, range 61.8-100.2 kg) for five females and 83.6 kg (SD=23.7, range 62.2-109.0 kg) for three males. Mean mass for eight animals of both sexes was 82.7 kg (SD=16.6). We were unable to weigh one male (estimated to be 95-100 kg) because of his struggling and the difficult position where he lay. This male probably was 21!22 months old, based on the length of his canine teeth. All others were pups of the year, approximately 9!10 months old. We deployed satellite-linked time-depth recorders (SLTDRs) and VHF transmitters on eight of the nine captured sea lions, not attaching instruments to the smallest of the female pups captured at Sequam Island. Via e-mail, we were able to notify colleagues at NMML immediately after SLTDR deployment, receiving confirmation within a few hours that each instrument was working and that each animal had shown some movement.
We successfully obtained blood from all captured animals. We performed preliminary blood work onboard the ship (e.g., serum extraction, hematocrit, white cell counts). Samples retained for later analyses in the laboratory included frozen serum and plasma, hemoglobin preserved in reagent, and blood smears on slides. The white-cell counts were very low for the two smallest pups, possibly an indication of viral infection. One of these pups also had ulcers on his foreflippers, possibly indicative of calicivirus infection. The largest female captured had an ulcer on her vulva that also may have been caused by calicivirus; however, her white cell count appeared within normal limits. We collected a genetic sample (flipper punch) from each captured animal, and a blubber biopsy from all five animals captured at Seguam Island and both animals captured at Long Island. The two animals captured at Aiktak Island were marginally restrained in an awkward setting and we decided to forgo biopsy. Blubber will be used for fatty acid studies as well as other analyses. Biopsies of one of the smaller flipper ulcers on the male pup at Long Island will be used for virology analysis.
We collected a fresh-born fetus on Sea Otter Island, at the northern end of the Kodiak Archipelago. Judging from the overall condition of the fetus, it had been born a few hours prior to our arrival. Partial inflation of the lungs implied that the pup had been born alive but had not survived more than 15-30 minutes. Dr. Terry Spraker of Colorado State University performed a postmortem examination onboard the ship and collected a full suite of formalin-preserved and frozen tissues for laboratory analyses. We also collected blood from the fetus, which we worked up according to the same protocols as for the live pups.
We had only two resightings of tagged animals. Both were tagged as new-born pups at Ugamak Island on 2 July 1998. We saw no branded sea lions during the cruise. In addition, we had surprisingly few observations of other marine mammals. We saw killer whales on only three occasions: two whales in Amukta Pass on 3 March, four whales in Tigalda Bay on 7 March, and five whales cruising processor row in Kodiak harbor on 12 March. We were unable to obtain photographs of any killer whales. On 3 March a group of 6-10 Pacific white-sided dolphins rode our bow for several minutes north of Akutan Island, near Unimak Pass.
The most notable bird observation was of a male spectacled eider off the sea lion haulout on the rocks northeast of Tigalda, a site identified as “Kaligagan Rocks” by the Alaska Maritime Wildlife Refuge biologists. It is thought that most spectacled eiders winter in polynyas (open waters in sea ice) in the Bering Sea near St. Lawrence and St. Matthews islands. The few sightings of these birds in the Aleutian Islands during winter likely is a function of low observer effort.
The capture technique of using hand-held hoop nets on land worked very well. This was only the second time we have applied this technique to Steller sea lions in Alaska. The technique does require liberal adaptation and improvisation to cope with the physiography of each site, local weather conditions, and haul-out distribution of the animals. On three occasions we experimented with using the skiff immediately in front of the haulout to herd and distract animals and drive them towards the capture team, who crept up from behind. The skiff-aided technique was successful at one haul-out site but yielded only near misses at two others. Favorable weather, of course, is key to the success of any field operations in maritime Alaska, particularly in midwinter. Captures are difficult at best when forced to approach animals from up-wind, and impossible when conditions prevent landing the scientific party on the beach.
We administered a dose of valium (1.1-2.0 cc, depending on the animal’s estimated weight) to each animal about 10 minutes before we started handling it. Each animal struggled while we attached the various restraints, but calmed down quickly thereafter, usually by the time we finished weighing and taking measurements. All animals lay still while we attached SLTDRs and took blubber biopsies; several appeared to sleep through much of the procedure. Valium greatly reduced the animals’ struggles to escape, which in turn reduced the amount of wrestling and fighting required to restrain them, and reduced total handling time. Valium undoubtedly minimized the overall stress experienced by captured animals.
As of 10 April 2000, all eight SLTDRs continue to transmit data, 36 to 43 days after deployment. Two of the sea lions have remained within about 10 km of the capture site. Four others travelled as far as 30-40 km away from their capture sites, visiting several haul-out sites. Two sea lions travelled extensively, paying extended visits to haulouts 100 km and 110 km from their capture sites at Aiktak and Long Islands. Results from analyses of dive data are not available at this time.
By John Sease.
APIS 2000 Cruise: Multidisciplinary Research into the Ecology and Behavior of Antarctic Pack Ice Seals
The research described here was conducted as part of the Antarctic Pack Ice Seals (APIS) Program, an international research effort formulated by the SCAR (Scientific Committee on Antarctic Research) Group of Specialists on Seals to consider the functional significance of upper trophic level predators in the Antarctic pack ice zone and to investigate the seals’ interactions with their biological and physical environments. Recognizing the high cost and logistic difficulties in undertaking research in the pack ice on a circumpolar scale, scientists from the United States, Australia, Germany, South Africa, Norway, and the United Kingdom collaborated to implement a multi-disciplinary science program that would be far greater than the sum of its parts
( Figure 1).
The pack ice region surrounding Antarctica contains at least 50% of the world’s population of seals, comprising about 80% of the world’s total pinniped biomass. As a group, these seals are among the dominant top predators in Southern Ocean ecosystems, and the fluctuations in their abundance, growth patterns, life histories, and behavior provide a potential source of information about environmental variability integrated over a wide range of spatial and temporal scales. Variations in top predator distribution, abundance, behavior, and physiology can provide valuable insights into locations of oceanographic features and areas of high secondary production.
One of the hypotheses being explored by the APIS Program suggests that there are measurable physical and biological features in the Southern Ocean that result in areas of high biological activity by upper trophic level predators. Environmental features such as the margin of the continental shelf, the physical characteristics of sea ice, ocean fronts, and icebergs, are thought to produce conditions that lead to high biomass sites within the pack ice region. These sites may provide protection from predators, concentrated prey resources, access to water for foraging activity, and preferred sites for animals to give birth or molt. Moreover, such sites appear to be preferentially chosen depending upon species’ sex, age, physiological condition, and general health characteristics. Preliminary data indicate a strong coupling between biological characteristics of the upper trophic level species and the physical features of the pack ice environment. However, there have only been rare opportunities to make simultaneous measurements assessing in detail the processes leading to high densities of upper trophic level species associated with such features.
Scientists from the United States took a multi-disciplinary approach when developing their contribution to the international APIS Program. A group of 17 principal investigators from 12 agencies and institutions were funded by the National Science Foundation’s Office of Polar Programs to undertake the APIS 2000 cruise, which focused on the pack ice zone of the Ross Sea. The total group of 31 scientists that participated in the APIS 2000 cruise had expertise in seal abundance and distribution, seal health and nutrition, seal population genetics and immunogenetics, seabird ecology, fish and squid ecology, zooplankton and krill ecology and physiology, sea ice dynamics, and physical oceanography. The following questions formed the foundation upon which the APIS 2000 investigators formulated hypotheses within their respective disciplines:
Within the sea ice zone in the eastern Ross/western Amundsen Seas in summer —
1. How is the distribution of upper trophic predators and their prey influenced by oceanic fronts and ecological features associated with bathymetry and sea ice?
2. Do biological features (e.g., prey composition and availability), have a stronger, direct influence on the distribution of upper trophic predators than do physical features (e.g., ice thickness, topography, floe size)?
3. Do upper trophic predators located in zones where their densities are relatively high exhibit behavioral and physiological characteristics that are different from those of predators in low density areas?
The APIS 2000 cruise departed Lyttleton, New Zealand, on 20 December 1999 and ended on the morning of 10 February 2000, when we arrived at McMurdo Station, Antarctica (Figure 2). The cruise was extremely productive and allowed us to accomplish a tremendous amount of research on the ecology and behavior of Antarctic pack ice seals and their biological and physical environment. The research vessel N.B. Palmer proved to be an outstanding platform for conducting the APIS Program’s multidisciplinary research. The helicopter detail sailing with us was also terrific, and the helicopters were a research tool that we utilized to the fullest extent that weather allowed. On a typical day, it was not unusual for our science activities to include two helicopters aloft flying seal surveys, two or three Zodiac boats supporting local seal work, divers, and sea ice sampling, and a CTD cast or HTI acoustic survey conducted from the ship. Net tows were conducted in the evening when the seals went in the water to feed.
A quick look at some summary numbers provides a hint of the intensity with which the APIS cruise was conducted: 45 science days, 647 separate science events, ship track sampling of approximately 800 km along the Ross Sea polynya marginal ice zone, nearly 1,000 km along the coastal fast ice, two short transects across the ice-covered shelf slope zone, four long transects from the coast to the northern marginal ice zone (each about 600 km long), and 175 hours of helicopter flights (which yielded well over 18,000 km of aerial survey transects for seals).
Seals: We had good success in deploying satellite-linked transmitters (PTTs) on seals to monitor their behavior (i.e., distribution, habitat selection, haul-out behavior, dive behavior). Although we had been concerned about the potential lack of molted seals that we might encounter at this time of year (i.e., early in the molt stage), we were able to find seals that were in increasingly advanced stages of molt. Because the PTTs are fastened to seals’ hair with an adhesive, it is most desirable to deploy instruments on seals that have already completed their annual molt; instruments deployed on unmolted seals at this time of year are likely to fall off within a matter of several weeks (in contrast to remaining active on a molted seal for several months to one year). We deployed satellite tags on all four species of Antarctic pack ice seals: crabeater (22), Ross (4), Weddell (3), and leopard (2) seals.
We were also very pleased with the results of our aerial surveys of seal abundance and distribution, which included good samples of all the major ecological sampling zones that we were targeting for the cruise: continental shelf, shelf slope, interior pack ice, and northern marginal ice zone. In total, aerial surveys conducted by the two helicopters staged from the ship surveyed 18,576 km of pack ice habitat by air, and observed 11,414 seals (4,817 crabeater, 2,852 Weddell, 79 Ross, 33 leopard, and 3,633 unidentified seals) and 11,066 emperor penguins With this thorough coverage, we observed an apparent latitudinal gradient in crabeater seal density along our four north-south transect lines. Density was highest in the vicinity of the shelf and slope (0.75 crabeater seals per square kilometer) and it decreased exponentially as we proceeded north over deeper water (0.22 and 0.24 seals per square kilometer in the mid-pack and northern ice edge, respectively). We observed a slight increase in crabeater seal density at the northern ice edge; this higher density only extended 10-20 km into the pack from the consolidated ice edge, and may have resulted from the recent on-ice winds which consolidated the receding ice in the marginal sea ice zone. These preliminary results support our hypotheses that physical fronts associated with the continental shelf and shelf slope are important ecological factors influencing the distribution of crabeater seals. Analyses of those counts will be enhanced by a superb set of sea ice data obtained from the belly-mounted digital video cameras used on all flights.
Samples to evaluate seal condition and nutrition were taken from 154 seals for blood analysis (53 Weddell, 58 crabeaters, 40 Ross, and 3 leopard seals) and 157 animals for detailed morphometric measurements.
More than 1,000 samples were shipped back to the United States for analysis, in addition to the analyses conducted on board the Palmer. Our preliminary data indicate that only about 10% of the seals had fed within 6 hours of capture, but only 1 of the 40 Ross seals met this criteria. This fits with the theory that Ross seals come to the ice pack for molting, a time period where most seals limit their feeding activity. Accordingly, our measurements of body fat levels are similar to values seen in other species of seals during the molting period and are on the lean side. Our ability to predict seal mass from length and girth measurements was quite strong, with a better than 0.99 correlation between predicted and actual. Taken together, these nutritional and body morphometric data will be combined with analysis of lipid types in both the seals and their prey items to construct a model of predator-prey relationships. Finally, when combined with the extensive distribution data for seals and trawling data for prey, we expect to be able to better model how nutritional status relates to seal distribution in the pack ice of the Ross Sea.
Biomedical samples were collected from over 130 seals. Our most complete data set is for crabeater seals, and we performed complete medical work-ups on 7-10 crabeaters in each of the zones sampled on the cruise (pack ice transects, the northern ice edge, and the southern polynya/coastal area). We performed 85 microbiological cultures on over 70 animals, including Salmonella screens, gastrointestinal tract flora examinations, and skin and wound cultures. Detailed anesthetic records were maintained on all seals immobilized during our handling events, and sera for drug level determinations will be submitted on a subset of animals. These data will allow us to recommend refinements to chemical immobilization protocols for Antarctic phocids.
A total of 432 samples was collected for population genetics and immunogenetics analyses, comprising 181 crabeater seals, 202 Weddell seals, 42 Ross seals, and 7 leopard seals. Few leopard seals were seen, as is reflected in the paucity of specimens from them, while we encountered Ross seals in much larger numbers than anticipated. Besides collecting skin samples for genetic analysis, our observations throughout the cruise gave us new ideas, perspectives, and insights into some of the ties between genetic heterozygosity and life history patterns. For example, crabeater seals are typically referred to as preferring pack ice and Weddell seals as preferring the fast ice. While we found this characterization to be generally true in the Ross Sea, we found large numbers of newly weaned pup and subadult crabeater seals in fast ice areas, in groupings similar to those we observed in the spring in the Antarctic Peninsula in the late 1970s, suggesting this phenomenon may be characteristic of young animals through more of the year than was previously thought. Older crabeater seals and fewer pups were found in the in the interior pack ice zone. From our preliminary genetic analyses, crabeater seals appeared to have little or no development of genetic population structure,suggesting they move extensively around the continent and breed in a panmictic fashion. Thus, it was particularly interesting to observe that, despite the scarcity of leopard seals, the scarring rates on crabeater seals was relatively high, suggesting the animals had received their wounds elsewhere than in the Ross Sea area. The tendency for these young seals to be so abundant in the fast ice could be related to food availability or to reducing their vulnerability to predators.
Conversely, we found larger numbers of Weddell seals than we expected in the interior pack ice zone, especially subadults and adults that appeared to have not yet entered the breeding population. The greatest number of these animals were found on large floes several kilomenters across and the seals themselves tended to be most common away from the edges, and in the middle of the floes, in habitat with considerable similarity to land fast ice. However, we are still puzzled by the predominance of younger, but apparently nonbreeding, adult Weddell seals in the land fast ice that were sampled to the east of Cape Colbeck. Only when we sampled Weddell seals in the rift cracks approximately 10 km south into the Ross Ice Shelf from the Bay of Whales did we find large breeding adult males and females, suggesting this is a fully established breeding colony. It is possible that the Weddell seals we sampled in the pack ice region originated from regions other than the eastern Ross Sea coastal area. Our genetic analyses will facilitate addressing this question since our analyses to date have shown significant genetic differences among populations of Weddell seals from different regions of the Antarctic.
Throughout the interior pack ice zone in the Ross Sea, we encountered an unusually large number of Ross seals, usually molting as single individuals on large floes. It is likely that the reason we saw so many Ross seals was that the seals were molting at the time we were in the pack ice. It has been hypothesized that they are normally pelagic for much of the year and, thus, are not usually seen. The molt of several individuals was characterized by shedding of large amounts of hair and sloughing of skin, in a fashion similar to elephant seals. This observation emphasizes the evolutionary aspects of the phylogenetic relationships between the Antarctic ice breeding seals and the elephant seals and monk seals which we hope to be able to examine. Our sample of 42 will allow us to make a statistically significant evaluation of genetic heterozygosity in this species and to compare the Ross seals of the eastern Ross Sea with those near the South African station, from which we also have a sample, albeit a smaller one.
Finally, from observations made by other programs on the ship, it appeared that the benthic community of the shelf region along the coast had a high biomass of fish and invertebrates. Although the pathways are not clear, it seems likely this high biomass and possibly the particular assemblage of species there may be partly responsible for the patterns of distribution of adult and subadult Weddell and crabeater seals we observed.
Seabirds: The APIS cruise made possible the closing of the gap in life history data for the emperor penguin. We were able to learn the physical nature of the ice pack on which they molt, how it declines in area over the minimum ice month of the year, and the character of the floes on which they spend the month molting. We also learned that one of the preferred areas for molting is on the fast ice in the shadow of Mt. Siple on the Marie Byrd Land coast. We were also able to determine body mass of the birds before and after the molt, a critical factor in their survival during this vulnerable period. Finally, we were also able to gain a better appreciation of who the emperor penguin’s neighbors and possible competitors are during this time in the eastern Ross Sea.
Fish, squid, and zooplankton: A total of 19 4-m2 MOCNESS tows , 22 9-m2 Tucker trawls, 5 15-m midwater trawl samples, and 6 15-m bottom tows were taken during the course of the APIS cruise, encompassing ice edge, deep pack ice, and shelf-slope environments. Midwater fauna were sampled in two basic depth strata: 0-500 m and 500-1,000 m. Bottom tows were executed on the shelf only, in depths ranging from 250 to 500 m.
Preliminary results from the study area, based on the general physiognomy of the trawls, suggest a few trends. First, the upper 500 m of the water column is nearly devoid of fishes, except over the shelf. The typical inhabitants of the midwater, the lanternfishes, are restricted to depths below 500 m and are very sparse there as well. Euphausiids, when present, dominate in the upper 200 m. The major predators captured by our midwater tows were large jellies such as Periphylla and Stygiomedusa. The bottom fauna on the shelf, in contrast to the midwater, was astoundingly rich in both fish and invertebrate species. Ten-minute tows produced hundreds of kilos of invertebrate biomass, and greater than twenty five species of fishes. Clearly, most of the marine life on the Ross Sea shelf is on the bottom.
Our preliminary results indicate that acoustic targets were most prevalent on the shelf in the coastal polynya, where dense layers and swarms were detected. Net tows suggested that these layers were composed primarily of the euphausiids, Euphausia crystallorophias and E. superba, and a juvenile fish, Pleuragramma antarcticum. Layers of euphausiids and juvenile Pleuragramma also were detected at a few stations along the ice edge of the Ross Sea polynya north of the shelf slope. Swarms were less frequent at stations in the interior and at the northern edge of the pack ice. In all regions, acoustic targets occurred primarily in the upper 100 m of the water column.
Assessments of krill and zooplankton using divers and net tows went very smoothly throughout the APIS cruise. We completed more than 58 dives and 49 net tows in a variety of coastal and offshore habitats. We saw a similar pattern for all four long transects, catching adult and 1-year-old Euphausia superba at the northern edge of the APIS area and Euphausia crystallorophias at the southern edge. The water column in the middle area of transect 4 was dominated by copepods and krill biomass was at a low for the transect. Diving observations correlated well with the net catches with the exception that the underside of the pack ice seems the province of 1-year-old and not adult Euphausia superba. Gravid adults Euphausia superba have dominated the net catches of krill along the northern ice edge, making this one of the richest areas surveyed in terms of energy available to seals.
Hydrography and sea ice: For the hydrography, CTD casts were accomplished throughout the study area on a spacing of 60 nmi or less, along with open water stations north and south of the ice edges on the ends of the transects. Regular near-surface sampling was done by the divers using a SeaCat CTD and under-ice sampling of water for isotopes during most of the daily dives. An additional seven ice cores were obtained on the last two transects at the daily stops and give a roughly regular grid of sea ice cores across the study area. On the stop at Bartlett Inlet near Cape Colbeck, small chunks of green iceberg were observed, and we sampled three of these pieces from the Zodiac. Analyses are under way on ice structure, particulate content, chemical composition and subsampling for oxygen isotopes.
By John L. Bengtson.
Gray Whale Strandings
In 1999, an unusually high number of gray whales (273) stranded along the west coast of North America (see summary by S. Moore in AFSC Quarterly Report, October-December 1999), which caused NMFS to consult the Working Group on Marine Mammal Unusual Mortality Events in July 1999. The group decided that this qualified as an unusual mortality event, and an evaluation was requested. NMFS contracted with Stephanie Norman to complete this evaluation. The draft report (Gray Whale Strandings in 1999 and a Review of Stranding Records in 1995-1998 by Stephanie A. Norman, Marcia M. Muto, David J. Rugh, and Sue E. Moore) includes a summary of all available data; a review of the stranding response; an assessment of the impact of the mortality event on the affected population; and a list of potential causes for the event.
Several factors may have contributed to the high number of gray whale strandings in 1999:
chemical contaminants - overall, contaminant levels in the whales that stranded in 1998/99 were not significantly higher than expected, suggesting that pollution was probably not the primary cause of death
natural toxins - at this time, there is no definitive evidence that biotoxins contributed to the increased number of gray whale strandings
disease - although it is unlikely that all the gray whale mortalities in 1999 were caused by disease, the possibility of an infectious agent compromising an individual’s resistance to opportunistic disease cannot be discounted
fishery interactions and ship strikes - only two stranded animals were entangled in fishing gear and there were no confirmed ship strikes
wind and current effects - variables such as the number of whales passing through the area, current strength and direction, and duration of onshore winds influence the likelihood of a dead whale reaching the shore and its condition upon stranding
starvation - the emaciated condition reported for some of the stranded whales supports the speculation that starvation may be one of several causative factors related to the observed the primary cause of the mortalities in 1999; however, there are no data to support or refute this contention.
Given the expected
natural mortality for a population now estimated in
excess of 26,600 whales, the high number of stranded
animals observed in 1999 most likely did not have a
deleterious effect on the overall population.
By David Rugh and Marcia Muto.
Status of Cook Inlet Beluga Whales
The National Marine Mammal Laboratory (NMML) in conjunction with other researchers conducting studies in Cook Inlet, Alaska, is preparing manuscripts summarizing available information on beluga whales (Delphinapterus leucas) from the Cook Inlet stock. Beluga whales occur in five stocks around Alaska, the most isolated of which is the Cook Inlet population. The geographic and genetic segregation of this stock, combined with their tendency toward site fidelity in summer, makes this population especially vulnerable to deleterious impacts from large or persistent harvests. Results from 6 years (1993-98) of summer aerial surveys indicated that beluga distribution within Cook Inlet was shrinking, and estimated population size has declined by nearly 50%. Point estimates of annual abundance ranged from 653 whales in 1994 to 347 whales in 1998. This meant that the average reported harvest of belugas in Cook Inlet during this period (72 whales) was 21% of the best estimate of abundance. Relative to the total number of animals that can be safely removed annually from a population of marine mammals (referred to as the Potential Biological Removal (PBR) in the Marine Mammal Protection Act (MMPA) ), the harvest rate between 1994 and 1996 was approximately 5 times the calculated PBR of 14 whales. Notably, the PBR was later reduced to 1.6 whales when the calculations incorporated revised abundance estimates from surveys completed in 1998 and a revised recovery factor to account for the observed decline in abundance.
On 19 November 1998, NMFS initiated a formal review of the status of the Cook Inlet beluga stock through a cooperative process with the Alaska Beluga Whale Committee (ABWC) and the Cook Inlet Marine Mammal Council (CIMMC). The objective of this review was to provide recommendations to the Alaska Regional Office and the NMFS Office of Protected Resources regarding the classification of this stock as endangered or threatened under the Endangered Species Act (ESA) or depleted under the MMPA. The scientific portion of the review focused on the current status of Cook Inlet belugas: distribution, abundance, trends in abundance, and habitat. The effects of the Alaska Native subsistence harvest and the potential effects of other anthropogenic impacts, as well as beluga natural mortality were also examined. Manuscripts covering these topics will be published in a special issue of Marine Fisheries Review in summer 2000.
By Sue Moore and Doug DeMaster.
Alaska Eskimo Whaling Commission’s Initial Mitigation Meeting on Bowhead Whales
On 24 February 2000, NMML held a meeting called by the Alaska Eskimo Whaling Commission (AEWC) to discuss concerns about the impacts of oil and gas development on subsistence use of bowhead whales and on the communities of the North Slope Borough in general. Participants included members of the AEWC, the Barrow Whaling Captains, representatives from the North Slope Borough, British Petroleum, ARCO Alaska, Phillips Petroleum, LGL, Clearwater Environmental, U.S. Minerals Management Service, and staff from NMFS Headquarters, NMFS’ Alaska Region, and NMML.
The focus of the meeting was to develop a process for addressing the following issues:
1) potential sources of adverse impacts to bowhead whales and subsistence hunting
2) how can threats be addressed and mitigated
3) how will impacts, including cumulative effects, be monitored
4) establish procedures for assessing and compensating for any damages caused by oil development and production.
recommendations included convening interagency
workshops to coordinate agency activities related to
monitoring the impacts of oil and gas development,
clarifying the legislative and administrative
authorities of various agencies with respect to oil
and gas development, and collecting suggestions for
resolving concerns about oil and gas development
from the North Slope Borough communities. A
draft report of the meeting was circulated to
participants in early March, and a final report will
be distributed by late spring 2000.
By Robyn Angliss.
Harbor Seal Task
The Alaska harbor seal task developed procedures to digitally grab photographs taken during the Aleutian Islands assessment survey flown during late summer 1999. These images were archived on CD-ROMs, digitally enhanced, and pulled into an image analysis program. Procedures were developed to seam overlapping images into one panoramic image per haulout. Seals were first counted in all assessment images using the traditional method of projecting slides onto counting boards. A sample of these counts was compared to counts taken using the new digital method. Initial results indicate that the digital method is not always a more effective way to count seals. In particular, images of harbor seals taken during the Aleutian Island survey typically showed dark-colored seals on dark wet rocks in extremely low light conditions; under these circumstances, the seals in the digitized image were not any easier to detect, even with a variety of image enhancement tools available. However, the technique appears to work quite well for seals hauling out on other substrates, such as sand, which provides better contrast.
Last summer, nine harbor seals associated with the glacial ice in Tracy Arm, Southeast Alaska were captured and fitted with time-depth recorders (TDR). A series of three remote data collection computers (DCC) were placed in Tracy Arm to monitor the presence or absence of the tagged seals and to determine whether individual seals were in the glacial fjord or in Stephens Passage. In early 2000, programs were written to analyze the DCC data in preparation for a comparison with the haul-out and diving behavior data from the TDRs.
By Robyn Angliss.