NMML Report JAS '99

Steller Sea Lion Field Studies at Marmot Island

Marmot Island, located 45 km northeast of Kodiak Island in the Gulf of Alaska, has been the site of land-based studies of Steller sea lions (Eumetopias jubatus) for more than 20 years. Most of the work has been conducted cooperatively between the National Marine Mammal Laboratory (NMML) and the Alaska Department of Fish and Game (ADF&G). The island once supported one of the largest Steller sea lion rookeries in Alaska, but numbers of pups and non-pups (adults and juveniles) counted during the breeding season have declined dramatically since the 1970s. Marmot Island is currently considered both a trend site and a trend rookery used to identify and monitor Steller sea lion population trends in the central Gulf of Alaska.

Researchers from the NMML Alaska Ecosystems Program conducted studies at Marmot Island from 7 June to 11 July 1999 during the pupping and breeding season. Objectives of the study were to continue monitoring the population of Steller sea lions through counts by age and sex class (territorial males, nonterritorial males, females, juveniles, and pups) and by resightings of branded and tagged animals. The census was conducted from cliff-top sites and included daily counts of beaches 1-4, weekly counts of beaches 5-7, weekly dawn-to-dusk hourly counts of beach 4, plus additional, twice-daily brand observations at beaches 1-4. Currently, only beaches 4 and 7 are rookeries, beach 3 is actively used as a male haulout, beaches 1 and 3Z are frequented by only a few males, and beaches 2, 5, and 6 have been abandoned. The preponderance of fog this year precluded counting on 6 of 34 days and counting beaches 5-7 during the first 3 weeks of the study. Beach 7 was counted only twice and beaches 5 and 6 were each surveyed three times, although no sea lions were observed. Maximum counts at beach 4 were 293 females, 269 pups, 25 juveniles, 41 territorial males, and 6 nonterritorial males. Maximum counts at beach 7 were 213 females, 233 pups, 26 juveniles, 29 territorial males, and 5 non-territorial males. A single day, island-wide census was possible on only two occasions. The maximum island-wide count (3 July, all beaches combined) was 413 females, 499 pups, 37 juveniles, 52 territorial males, and 74 non-territorial males, for a total of 1,075 sea lions. Approximately 750 pups were branded at Marmot Island during 1987 and 1988, yet only 6 of those were resighted during 1999. Five were males, and one was a female with a pup. Two other branded males that were sighted included a subadult from Forrester Island and another whose brand origin is presently unknown. Preliminary review of the 1999 data suggests that the Marmot Island population is continuing to decline.

By Lisa Baraff.

Bogoslof Island Research

The following research was conducted at Bogoslof Island, Alaska, and en route to Adak while aboard the U.S. Fish and Wildlife Service (USFWS) research vessel Tiglax from 31 July to 5 August 1999.

An underwater survey was made on the afternoon of 1 August to assess the suitability of Bogoslof Island as an underwater capture site for Steller sea lions. The dive lasted 20 minutes, and the maximum depth reached was 50 ft. Most of the dive was spent in depths of 30-40 ft among large boulders, many of which had kelp attached. Wave surge was present even at maximum depths reached. We were accompanied by subadult male northern fur seals throughout the dive, although no aggressive behavior was observed. Very little marine fauna was present in the area, and only one small school of fish, possibly juvenile or larval greenlings, was seen.

By Bruce Robson.

Northern Fur Seal Foraging Ecology

Scientists from the NMML conducted research on the summer foraging ecology of juvenile male northern fur seals in the Bering Sea from 26 July to 30 August 1999 on St. Paul Island, Alaska. Juvenile males form a large component of the population that actively forages during the summer. Recent studies of northern fur seal foraging ecology have focused on females with pups, but little is known about the utilization of the Bering Sea by juvenile males and whether aspects of their foraging behavior overlap with that of female fur seals. The objectives of our research were to investigate the travel routes, foraging habitat, and diving behavior of these juvenile male fur seals.

Fifteen juvenile males, 3-5 years of age (35-85 kg), were captured and instrumented with satellite transmitters to provide location data at sea. Seven of these animals were also instrumented with time-depth recorders for analysis of diving behavior. Multiple foraging trips were recorded for two of the animals and, as of October 1999, some of the recorders were still transmitting data. The maximum distance recorded at sea from the location of capture for each of 13 foraging trips (11 individuals) ranged from 88 to 1,015 km, and the mean was over 490 km. The duration of nine completed foraging trips (eight individuals) ranged from 6 to 30 days, and the mean was 17 days. Foraging trips of six female fur seals instrumented during summer 1998 had a mean maximum distance of 274 km and a mean foraging duration less than 10 days. Preliminary data indicate that juvenile male foraging behavior differs from that of females in duration of foraging trips and in utilization of Bering Sea habitat.

Data were also collected for monitoring pup condition and fur seal food habits during summer 1999. Pup weight, length, and sex data were collected from 1,082 pups during 24-25 August, and scats were collected for examining food habits of northern fur seals.

By Rolf Ream.

Tagging of Beluga Whale in Cook Inlet, Alaska

From 24 May to 3 June 1999, biologists from NMML and the NMFS Anchorage Field Office tested new techniques for capturing and tagging beluga whales in upper Cook Inlet, Alaska. Animals equipped with satellite-linked-time-depth-recorders (SLTDRs) are needed to provide data on surfacing and dive patterns as well as distribution and movements. In particular, the surfacing interval data are critical for developing a correction factor to account for beluga whales not at the surface (and thus not visible) at the time of aerial surveys.

The study area encompassed the wide tidal deltas between the Big and Little Susitna Rivers, approximately 50 km southwest of Anchorage. A crew of seven, based in a field camp at the mouth of the Big Susitna River, searched for beluga whales during each high tide when conditions were adequate for small boat operation. Once animals were located in shallow water, a 125-m gill net was set at high speed around a target whale. Despite problems with the capture net tangling in tight, high-speed turns, four whales were caught. This marked the first successful capture of beluga whales in Upper Cook Inlet. We equipped one of the four animals, a 370-cm adult male, with a satellite TDR and VHF combination tag; one 230-cm immature female too small to tag was measured and released; one adult escaped during handling; and one adult escaped at the onset of handling.

The tagged animal was tracked by boat in early June following the VHF signal, yielding over 10 hrs of detailed observation and surfacing interval data to be compared with the satellite-based data set. The satellite tag transmitted location and dive data for a total of 112 days, having either lost power or fallen off on 17 September. A larger capture effort using further modifications of the gill-net encirclement technique are planned for May and June 2000 in the same area.

By Rich Ferrero.

Cetacean Surveys Aboard Sir Wilfrid Laurier

Sue Moore of the NMML met the Canadian Coast Guard Icebreaker (CCGI) Sir Wilfrid Laurier in Barrow, Alaska, on 20 July 1999 where she participated in a cruise to study the ecology of marine organisms along the ice edge and in the Beaufort Sea. Extensive sea ice caused postponement of mooring and oceanographic work, and U.S., Canadian, and Japanese oceanographers departed Barrow on 22 July. The ship remained in the Barrow area until 25 July, waiting for wind conditions to induce sea ice movement offshore. On 25 July, the decision was made to begin a crossing of the Alaskan Beaufort Sea along the only available route close to shore. Prior to departing Barrow, a 2-hour aerial survey of the Barrow Canyon area was conducted by helicopter, and a watch for marine mammals from the ship’s bridge was initiated. Eight bowhead whales were seen during the search: two from the helicopter and six from the ship (Table 1 below). Whales were observed resting, swimming, or feeding. The whales seen from the helicopter (surveying at 1,000-ft altitude) reacted to circling passes by sinking from sight (i.e., no rounding on dives). Four of the whales seen from the ship appeared to be feeding.

Two gray whales were also seen on 25 July, just north of Dease Inlet (71�14.7’N, 155�22.1’W) in 50% ice cover. These two whales appeared to be juveniles (small) and initially tried to outrun the vessel while maintaining very low profiles as they surfaced to breathe. As the ship passed the whales, one whale turned sharply and slapped its fluke on the water. Prior to departing Barrow, gray whales had been observed from the stationary ship (71�17.7’N, 156�49.7’W) on two occasions: a cow/calf pair was observed on 24 July, and a juvenile whale was observed on 25 July.

No other cetaceans were seen during the remainder of the cruise, although the crew of the Laurier made several cetacean and pinniped sightings prior to 20 July and have recorded sightings since 27 July. These opportunistic sightings are being recorded on NMML Platform of Opportunity data forms. Although ice conditions curtailed plans to survey the Beaufort Sea slope, it is noteworthy that bowhead whales were seen near Barrow in July, a time of year when the Bering-Chukchi-Beaufort stock is expected to be in the Canadian Arctic.

By Sue Moore.

Humpback Whale Survey

A study of humpback whale distribution in Washington State waters in the vicinity of Cape Flattery was conducted as a collaboration between the NMML and Cascadia Research (CR), facilitated by the Olympic Coast National Marine Sanctuary (OCNMS). Survey tracklines were proposed to complement ongoing research conducted by CR. Survey protocol included photo-identification and biopsy sampling. Biopsy samples were collected only after fluke identification shots were obtained.

Surveys were conducted during 3-5 August 1999 on the OCNMS vessel OC-2, a Zodiac Hurricane 630, rigid hull inflatable, captained by Andy Palmer, on contract to OCNMS (Tables 2 and 3 below). Six sightings occurred of one or more humpback whales, comprising a total of seven individuals. Two sightings of gray whales occurred comprising three individuals. Humpback whale fluke photographs were taken of five individual whales. One adult humpback whale and one humpback whale calf whale were not photographed. Biopsy samples were obtained from four whales (all but one of the adult humpback whales encountered). Gray whales were not biopsy targets during this survey but were included in this survey as encountered and photographed for identification.

The humpback whale photographs have been printed and entered in the NMML North Pacific humpback whale database.

Two of the five individual whales photographed during this survey had been photographed previously. The cow on 3 August 1999 was first photographed and observed off La Perouse Bank in 1991 (NMMLID 16614 and CWR ID 14209). The whale observed on 3 August 1999 (encounter OC-3) was previously photographed off California in 1992 and off Washington in 1995 (NMMLID 25975 and CRC ID 10654)

By Sally Mizroch.

Cetacean Survey Aboard the John N. Cobb

NMML scientists conducted a cetacean survey aboard the NOAA research vessel John N. Cobb 10-23 September 1999 in Southeast Alaska. The purpose of the study was to collect information on the distribution, abundance, and stock structure of cetaceans, particularly killer whales, Orcinus orca, in Southeast Alaska. Biopsy samples were collected also to investigate genetic diversity, dietary preferences, and contaminant levels of North Pacific killer whales. Underwater recordings of cetacean sounds were made to add to NMML’s acoustic library.

Approximately 1,930 km of trackline were surveyed. Survey areas included all major inland waterways of Southeast Alaska ranging from Juneau to Ketchikan. Several species of cetaceans were observed including humpback whales, minke whales, killer whales, Dall’s porpoise, and harbor porpoise. Of particular note were the rare observations of a northern elephant seal in Chatham Strait and a northern fur seal in Frederick Sound. Skin samples collected from killer whales will be sent to the University of Durham (England) for genetic analysis. Contaminant studies using killer whale blubber samples are being conducted by NMML scientists in collaboration with the Northwest Fisheries Science Center (NWFSC).

By Marilyn Dahlheim.

Polar Ecosystem Program

The Harbor Seal Task of the NMML Polar Ecosystem Program conducted an aerial assessment survey of harbor seals along the Aleutian Islands from Unimak Pass to Attu Island during 5-15 August 1999. The survey is the second of two surveys conducted by the NMML specifically designed to assess harbor seal abundance along the Aleutian Islands; the first was conducted in 1994. One aircraft, a standard Grumman Goose, and observer were stationed in Dutch Harbor, Alaska, and surveyed east to Unimak Pass; a second aircraft, a turbo Commander, was also stationed in Dutch Harbor and surveyed west to the Fox Islands. A third aircraft, also a turbo Commander, was stationed in Atka and surveyed east to Amukta Pass. A fourth aircraft, a turbine Grumman Goose, surveyed from Adak Island west to Attu Island. Seal densities were low but similar to those in 1994. Several new haul-out sites were discovered.

Another field project was conducted in late August and early September from the John N. Cobb and a smaller skiff provided by the Canadian Department of Fisheries and Oceans. The work was a follow-up to field work conducted in April 1999, when nine TDRs were placed on seals hauling out on the glacial ice near south Sawyer Glacier (Tracy Arm) in Southeast Alaska. The purpose of the project is to develop a correction factor to account for seals in the water and not hauled out when aerial assessment surveys take place in August. Ancillary information on dive profiles, haul-out times, and possibly feeding can be determined from the TDR data. The TDR units are designed to be glued onto the backs of the seals and fall off during the late summer molt and then float, transmitting a signal that observers use to relocate the devices. Observers recovered seven of the nine devices (only three to five were realistically expected to be recovered). Data collection computers, which were strategically placed along Tracy Arm in April to record presence or absence of the tagged seals, were also recovered in early September.

By Dave Withrow.

California Current Program Field Studies Gray Whale Surveys

From June to August 1999, vessel surveys were conducted off the Washington coast, Vancouver Island, British Columbia, and in the Strait of Juan de Fuca to determine the abundance and distribution of gray whales. Surveys were conducted over 29 days, including a 14-day survey of the west coast of Vancouver Island and a 2-day survey of the Washington coast. Whenever possible, the whales were identified by photographs. A total of 89 gray whales were sighted during the survey and most were successfully photographed.