National Marine Mammal Laboratory

Beluga Tagging in Cook Inlet, August 2001

During 10-20 August 2001, members of the National Marine Mammal Laboratory (NMML), the Alaska Region Anchorage office, and the native village of Tyonek, Alaska, participated in a cooperative tagging project to attach satellite tags to seven beluga whales in Cook Inlet, Alaska. The first whale was captured in the little Susitna River and the remaining six whales were captured in Knik Arm. A 1,000-ft net was used to encircle the whales. Captured whales were quickly removed from the net and placed into a sling between rigid-hull inflatable boats. The sling was an innovation introduced this year, which allowed the tagging team to cut handling time per whale to less than an hour and avoid stranding the whale in shallow water. Once a whale was secured, one or two tags were surgically attached to its back, the animal was measured, and skin, blubber and blood samples were taken. The whale was then released.

Two types of tags were employed, and for five of the seven whales one of each type was attached.  Each of the seven whales was tagged with a small position-only tag (S). These tags are designed to stay on for 1-2 years but give locations only three to six times a month. Five of the whales also were tagged  with a dive tag (D), similar to the tags attached by this project in 1999 and 2000. Along with location several times a day, the dive tags report dive data but only last for 2-4 months. The long-term data from the position-only tag allow us to follow movements of the whales through an entire year and determine the distribution of the whales during the winter months when they are difficult to spot from an airplane due to ice cover and weather conditions. The dive tags give us more detailed location and dive data, including depths and durations of dives.  These data are important for determining how beluga whales use the habitat of Cook Inlet. Initial location data are shown in Figure 1 and Figure 2.  For the December tracking map click here.

The biopsy samples are used for various studies.  Skin samples provide genetic information.  Blubber samples are analyzed for diet and contaminant loads.  Blood samples provide information on general health, pathogens, parasites, and hormone levels.

By Rod Hobbs.


Instrument Testing on Northern Fur Seals

NMML scientists tested remote release devices for data collection instruments on adult female northern fur seals (Callorhinus ursinus) during 17 -31 August 2001 on St. Paul Island, Alaska.  Testing of the devices was designed for future use in studies on Steller sea lions, Eumetopias jubatus.  Scientists have deployed a number of data collection instruments on Steller sea lions; however, recovery of these instruments is rare due to the low probability of recapturing sea lions.  The instruments are expensive to replace and valuable dive and location data, stored in memory, are lost when the instruments are not recovered. Consequently, a device that could release the instruments from sea lions on land was determined desirable.  Two release platforms and a transmitter to trigger the release of the instruments were tested on adult female fur seals, due to their higher probability of recapture.

Two adult females (38.5 and 41.5 kg) were captured and instrumented with 1) a satellite-linked depth recorder (SDR) attached to a release platform, 2) a time-depth recorder (TDR), and 3) a VHF transmitter. A single foraging trip for each female was recorded for the purpose of testing initial durability of the release platform and the release mechanism.  Each foraging trip lasted 7 days.  Female “A” was the first to return to the island.  Personnel were positioned to recapture the animal prior to attempting to release the instrument.  A laser range-finder was used to estimate the distance from which the release was triggered.  Instrument “A” was triggered to release from a distance of 185 m.  Once personnel initiated the capture and the animal reacted, the instrument fell off the release platform, indicating a successful remote release.  The animal was then captured and the release platform and other instruments were removed.  Instrument “B” was initially triggered from 255 m, and then the animal was captured.  The release platform did not function.  The animal was restrained, the release was again triggered at distances of 175, 100, 60, 30 and 2 m.  The release did not function when triggered from any of these distances.

Once the design and performance of the release platform is improved, the remote release instruments should prove extremely useful to Steller sea lion and other pinniped research.

By Rod Towell.


California Current Research: Harbor Seals

The NMML and the Washington Department of Fish and Wildlife (WDFW) are conducting a collaborative study to determine reproductive success, survival, natality, and longevity of harbor seals in Washington State.  Observations of tagged and branded harbor seals began on 15 July at Gertrude Island in south Puget Sound, Washington, where about 100 pups were born between 15 July and 1 September.  Fifty harbor seals, primarily pups and subadults, were branded on 18-19 September.  In addition, blood from these branded seals was screened for Brucella and Leptospira antibodies.  Two seals tested positive for Brucella.

Three hundred scat samples were collected between 23 July and 18 September at the Columbia River to assess harbor seal predation on endangered salmonids.  From these samples, prey species will be identified morphologically from bones and otoliths. Unfortunately, salmonid bones can only be identified to family using morphological characteristics. The salmonid bones will therefore be identified to species using molecular genetics. In fall 2000, 27 percent of scat samples contained salmonid bones.


Gray Whales

From July to September 2001, gray whale surveys were conducted with a small vessel along the northern Washington coast, Strait of Juan de Fuca, and the west coast of Vancouver Island, Canada.  These surveys covered 1,046 nautical miles and took 76 hours.   One hundred fourteen gray whales were sighted and 54 of those were photographed for later identification. Skin biopsy samples were collected from four gray whales.  One survey extended as far south as Tillamook Bay along the northern Oregon coast. Only one gray whale was sighted in Oregon; it was off the mouth of the Nehalem River.  No gray whales were sighted in the Strait of Juan de Fuca. Sightings of gray whales increased along the northern Washington coast at the end of August and the beginning of September.  The greatest number of gray whales was seen off the southwest coast of Vancouver Island in early July.


Steller Sea Lions

As part of a larger study on food habits and assessment of Steller sea lions in Washington, Oregon, and California, NMML staff collected scat twice a month from haul-out sites on the northern Washington coast and conducted bimonthly aerial and vessel surveys in collaboration with the  WDFW from July through September.  In late June, 180 Steller sea lion pups were tagged and branded at Rogue Reef, Oregon, in a cooperative study between NMML and the Oregon Department of Fish and Wildlife.  This is the beginning of a long-term project to estimate survival and natality for the Oregon population of Steller sea lions.


California Sea Lions and Northern Fur Seals

Population assessment studies of California sea lions and northern fur seals were conducted at San Miguel Island, California, from 18 May to 8 August 2001.  California sea lion pup production increased 2.0 percent from pup production in 2000.  The observed sea lion pup mortality rate through the first 4 months of life was 44.2 percent.   The high pup mortality is associated with a high incidence of hookworm infections in young pups.  Northern fur seal pup production increased 23.7 percent from pup production in 2000, but still remains 33.7 percent below 1997 pup production, indicating that the 1997-98 El Niño event has had a long-term impact on this species.  A total of 6,799 sightings of branded California sea lions was recorded, representing 1,522 individuals. Four hundred sixty-five California sea lion females from 4 to 14 years old were sighted with pups. Observations of marked California sea lions will be used to estimate survival and natality rates for the population.   Five hundred California sea lions were branded at San Miguel Island to continue studies of survival and natality of the population. A study comparing foraging ecology of California sea lions and northern fur seal females was initiated in summer 2001. Preliminary results indicate that both species feed along the central California coast, however, northern fur seals forage farther off shore, along the continental slope, while California sea lions forage over the continental shelf.

By Harriet Huber.


Killer Whales in Central and Western Alaska:
Population Size and Stock Structure Background

The documented decline of Steller sea lions, harbor seals, and sea otters in the western Gulf of Alaska and the Bering Sea has raised questions about the potential impact that killer whale predation may have on these populations. Although killer whale population size and stock structure is well documented for the waters of Southeast Alaska and Prince William Sound, this is not so for killer whales inhabiting central and western Alaskan waters.  Dedicated surveys for killer whales in central and western Alaska occurred only in 1992 and 1993.  Minimum counts of killer whales, ranging from the western Gulf of Alaska to the Bering Sea (including the eastern and central Aleutian Islands) were obtained through photo-identification studies.  In addition to the photographic data collected during dedicated surveys, fisheries observers working with the Center’s RACE Division also collect photographic data of killer whales.  Analyses of photographic data collected through these combined efforts have resulted in the identification of approximately 400 individual whales from central and western Alaska.  Based on the preliminary analyses of photographic and behavioral data, it is apparent that both resident (primarily fish-eating) and transient (primarily mammal-eating) forms of killer whales inhabit central and western Alaskan waters.  A third ecotype of killer whale (first described in Canadian waters) also has been observed in Alaska and is termed the “offshore” type.  In Alaska, offshore killer whales have been seen only as far north as the inland waterways of Southeast Alaska.  Most of the killer whale information available from central and western Alaska pertains to the resident form.  Large aggregations of resident whales have been observed and are frequently reported off the eastern side of Kodiak Island, waters surrounding the Trinity Islands, Unimak Pass,  and the north side of Unalaska Island.  Transient whales, typically occurring in smaller groups, have been observed throughout the study area.  Out of the 400 photo-identified whales, approximately 40 whales have been provisionally classified as transients (less than 10% of total population).

2001 Research Activities
In an effort to expand upon the killer whale work described above, NMML initiated a 3-year study aimed at killer whale population size and stock structure in central and western Alaskan waters.  Scientists conducted dedicated killer whale studies aboard the chartered fishing vessel   Aleutian Mariner  from  Resurrection Bay (Seward, Alaska) to Seguam Pass (Central Aleutian Islands)  between 17 July and 25 August 2001.  The survey objectives were to:

1. Estimate abundance of central and western Alaskan killer whales ranging from Resurrection Bay to the central Aleutian Islands (Seguam Pass) using line transect, photo-identification, and mark/recapture photographic techniques.
     
2. Plot distribution and determine home ranges of identified pods of Alaska killer whales.?
     
3. Determine the ecotype (resident, transient, and offshore) of killer whale pods by examining differences in morphology from photographs, genetics from biopsy sampling, and analyses of acoustic recordings.  

Preliminary Results
During the 40-day survey (17 July to 25 August 2001), 1,937 nmi of  “on-effort” trackline were completed.  There were 19 encounters with killer whales (Figure 1) with provisional groupings as follows: 10 groups of resident whales (approximately 290 whales), 8 groups of transient whales (approximately 30 whales),  and 1 group of 40 offshore whales.  Photographs were collected for 18 of 19 encounters on 138 rolls of black and white Fuji 1600 film.  Frame by frame photographic analyses will yield a count of all individual whales observed.  A total of 17 biopsy samples were collected from 11 different killer whale groups. Genetic studies will be used to verify the pod’s ecotype as resident, transient, or offshore.  Tissue samples will also be analyzed for contaminant levels and compared to killer whale tissue samples collected from California to Alaska.  Underwater recordings were attempted on six occasions with killer whale calls recorded in four cases. Whenever possible, acoustic analyses will also be used to confirm the identification of resident versus transient pods.  Despite the number of encounters of killer whales seen during the survey,  predation by killer whales on a marine mammal was only observed once.  They were noted attacking and subsequently killing a small minke whale near a Steller sea lion rookery in the Shumagin Islands.

Numerous other cetacean species were observed during the survey. Total group sightings included  humpback whales (152), fin whales (86), gray whales (22), minke whales (33), sperm whales (7), beaked whales (1), Dall’s porpoise (156), and harbor porpoise (9).

Photographs of humpback whale flukes were collected whenever possible on a not-to-interfere basis with the killer whale studies.  Biopsy samples were collected from humpback whales, fin whales, and gray whales.

By Marilyn Dahlheim.


Harbor Seal Survey in Gulf of Alaska

The Polar Ecosystems Program conducts counts of harbor seals in Alaska for estimation of population abundance and long-term trends.  The harbor seal population is divided into five counting regions, one of which is surveyed annually during August when seals molt and spend more time ashore. The Gulf of Alaska (GOA) region, which includes the south side of the Alaska Peninsula and runs from Unimak Pass to Kayak Island east of Prince William Sound, is of particular concern because harbor seals have declined as much as 85 percent since the mid-1970s in some parts of the region.

The region was divided into routes that could be surveyed by aerial observers within the 4-hour period around low tide, which is best for counting harbor seals on shore.  The survey counts on these routes are replicated 4-5 days for acceptable precision of the estimates.   The most recent survey of the GOA region  required 13 routes using 13 separate aircraft with observers from NMML and the Alaska Department of Fish and Game.  Eleven routes were surveyed during 14-25 August 2001, and in anticipation of the logistical complexity of the 2001 survey season, surveys of the other two routes were conducted during August 2000 in conjunction with surveys of the Bristol Bay region.  Observers spent the first 3-5 days in reconnaissance of the entire coastline along their survey routes.  Locations of all seal haul-out sites were recorded and mapped using a global positioning system (GPS).  The remaining surveys were flown from site to site when the timing of the low tide was appropriate for counting harbor seals.  Visual counts were conducted for small groups of seals (<10), and aerial photgraphs were made of larger groups for subsequent counting at the NMML facilities in Seattle.

The GOA region is large and complex and difficult to survey adequately for harbor seal abundance.  Harbor seals haul out on sand or rock, and as many as 20 percent of the GOA seals haul out on ice calved from glaciers.  Seals hauled out on glacial ice pose special difficulties for surveys.  Ice is dispersed and in constant motion throughout glacial fjords, making it difficult to track what ice and seals have been surveyed.  Moreover, glacial ice frequently contains dirt and rocks, which complicates detecting and counting seals.

The GOA  region contains at least 14 glacial haul-out sites. During the 2001 survey, NMML contracted with Aero Map of Anchorage, Alaska, to photograph these sites using a GPS-linked large-format aerial mapping system.  Photos of the glacial sites were taken at various altitudes between 600 and 1,600 m  (2,000 and 5,000 feet) during the same time as our regular aerial abundance surveys described above.  Future plans are to repeat the large format surveys in the spring during the pupping period and to use a second contractor to photograph the glacial sites using an infrared system that may aid in discriminating between seals and rocks on the ice.

By David Withrow and Peter Boveng.
 

Up

AFSC Quarterly
Research Reports
July-Sept 2001