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National Marine Mammal Laboratory (NMML)

Aerial Surveys of Beluga Whales in Cook Inlet, Alaska, June 2002

Map showing aerial aerial survey of belugas in Cook Inlet, see text for explanation
 Figure 1. Aerial survey effort and beluga groups seen in Cook Inlet during flights conducted 4-11 June 2002. All whales were near river mouths or in shallow coastal waters of the northern part of the inlet. The survey covered all coastal areas and 1,234 km of offshore waters. Most of the northern part of the inlet was surveyed six times, but only one representative trackline is shown here.

NMFS biologists conducted an aerial survey of the beluga whale population in Cook Inlet, Alaska, during 4-11 June 2002 (Fig. 1).  The 45-hour survey was flown in a twin-engine, high-wing aircraft at an altitude of 244 m (800 ft) and speed of 185 km/hr (100 kt), consistent with NMFS annual surveys since 1993.  The flights in June 2002 included one or more surveys of coastal areas (flown 1.4 km off shore) around the entire inlet and 1,234 km of transects across the inlet, effectively searching more than 26% of Cook Inlet but nearly 100% of the coastal areas.  Paired, independent observers searched on the coastal (left) side of the plane, where virtually all beluga sightings occur, while a single observer was on the right.  A computer operator/data recorder was also on the left side.  After finding beluga groups, a series of aerial passes were made with two pairs of primary observers each making four or more independent counts of each group.

Median counts made in optimal viewing conditions on 2 to 6 different days were 0-93 belugas in the Susitna Delta (the northwesternmost portion of Cook Inlet), 54-97 in Knik Arm (the northeast corner of the inlet, north of Anchorage), and 10-11 in Chickaloon Bay (south of Anchorage).  There appeared to be exchanges of whales between the Susitna and Knik areas.  All of these sightings were in upper Cook Inlet.  No belugas were seen elsewhere.  This sighting distribution has been consistent most years since 1996;  however, prior to then, belugas were often seen farther south in the inlet.  In 2002, no belugas were encountered south of the Forelands in lower Cook Inlet even though many other marine mammals were seen there: 1,481 harbor seals (Phoca vitulina, in 57 sightings, of which 270 seals were at Fox River and 492 in Iniskin Bay); 151 sea otters (Enhydra lutris, in 27 sightings, all coastal and south of 59E47’N); 54 Steller sea lions (Eumetopias jubatus, in 6 sightings all in Kamishak Bay except for 2 sea lions  near Elizabeth Island); and 20 humpback whales (Megaptera novaeangliae, in groups of 1-3 each scattered along the southern boundary of Cook Inlet).  All of these species were seen in the relatively clear water of Kamishak and Kachemak Bays.  During our 8-day survey period, the only marine mammals seen in the opaque waters of the upper inlet were harbor seals and belugas. The sum of the median aerial estimates of belugas (a very rough but quick index of relative abundance, not corrected for estimates of whales missed) for June 2002 is 192.  This is below index counts for years prior to 1998 (305 in 1993, 281 in 1994, 324 in 1995, 307 in 1996, and 264 in 1997), but it is essentially the same as counts made during the past 4 years (193 in 1998, 217 in 1999, 184 in 2000,  and 211 in 2001).

By Dave Rugh.


Evaluation of Potential Harbor Seal Study Sites

Staff from the National Marine Mammal Laboratory (NMML) conducted a 2-week survey in June of six potential sites for a focused, long-term study of harbor seals in the Gulf of Alaska.  Harbor seals in the Gulf of Alaska have declined in numbers during the past 20 years, with the specific causes of the decline still undefined.  If NMML biologists are able to establish a long-term research program in the Gulf of Alaska, the research will provide critical insight into the population dynamics of these seals during this period of low population size.  We will be able to track vital rates such as pup production, age-specific survival, and mortality, as Gulf of Alaska harbor seals either recover or continue to decline.  This research program will also complement a similar study conducted by the Alaska Department of Fish and Game (ADF&G) at Tugidak Island, Alaska.

The goal of the June survey was to locate one or more sites suitable for establishing a long-term research station where a local population of harbor seals could be studied extensively.  The survey focused on areas with large concentrations of harbor seals: Middleton Island south of Prince William Sound; Orca Inlet, Olsen Bay, the Green Island-Northern Montague Island region, and Mears Glacier in Prince William Sound; and Kachemak Bay and Augustine Island in Cook Inlet.  Harbor seals were observed at each site, although at most sites the seals did not haul out close enough to shore for shore-based observations and photo-identification.  Based on the survey, NMML staff will revisit the most promising site, Augustine Island, in August 2002 for a more thorough evaluation of that site.

By Mike Simpkins and John Bengtson.


Resight Surveys for Branded Steller Sea Lions in Gulf of Alaska and Eastern Aleutian Islands

During the last 2 weeks of May 2002, NMML personnel conducted two simultaneous ship-based surveys of branded Steller sea lions in the Gulf of Alaska and the eastern Aleutian Islands region and provided significant support for a third cruise in the eastern Gulf of Alaska and Prince William Sound.  The NMML and ADF&G are using hot-branding as a technique for permanently marking Steller sea lions at various locations in Alaska.  The NMML began branding pups from western stock rookeries in the Gulf of Alaska and eastern Aleutian Islands in 2000.  The ADF&G began branding pups from the eastern stock at rookeries in Southeast Alaska in 1994.  These unique brands allow for identification of individual sea lions, which is important for estimating vital rates (e.g., age-specific survival) and allow for interpretation of sea lion dispersal and movement patterns.  The NMML and ADF&G first used hot-branding as a technique for permanently marking Steller sea lions at various locations in Alaska in the late 1970s and during 1987-88.  Few of those Steller sea lions are still alive given the species’ natural life expectancy of less than 15 years.

During 17-30 May, three NMML scientists visited 35 rookery and haul-out sites between Dutch Harbor and Kodiak Island aboard the chartered fishing vessel Muir Milach.  Most of the resight effort for this cruise was in the area of the Krenitzen Islands and Unimak Pass (eastern Aleutian Islands region), followed by visits to sites along the south side of the Alaska Peninsula during transit to Kodiak.  We identified 23 branded sea lions among a total of approximately 3,500 sea lions observed at all sites.  Of the branded sea lions, 19 were branded during 2001 as newborn pups at their natal rookery on Ugamak Island.  The other four anmals were captured and branded as juveniles by ADF&G scientists.

Two NMML scientists conducted resight effort in the central Gulf of Alaska aboard the chartered fishing vessel Big Valley during 18-31 May.  The cruise visited 35 rookeries and haul-out sites from the Semidi Islands along the Alaska Peninsula to the western Kenai Peninsula, including the Kodiak Archipelago, Shelikof Strait, and the Barren Islands.  Among a total of approximately 2,000 sea lions there were 28 identified brands.  Most of the resighted animals were branded as newborn pups at Marmot (n = 14) or Sugarloaf (n = 9) rookeries in July 2000.  One animal was branded as a juvenile during winter captures in the Kodiak area in March 2001. Four of the resighted sea lions had been branded as newborn pups on Marmot Island in 1987 and 1988; three were territorial males  resighted on Marmot Island and one was an adult female resighted on Sugarloaf Island.  An additional eight animals were resighted with flipper tags applied during various research efforts in the Kodiak area.

During the third cruise, personnel from the Alaska Sea Life Center counted approximately 1,600 sea lions at 23 sites in the eastern Gulf of Alaska and Prince William Sound from 14 to 22 May.  The 49 brand resights included 1 animal branded at Marmot Island  in 1988; 2 from Marmot and 7 from Sugarloaf Island branded in 2000; 14 from Seal Rocks and 10 from Fish Island branded in 2001; and 15 branded as juveniles during a variety of ADF&G and NMML capture trips.

During these surveys, NMML personnel collected fecal samples for diet studies and hormone analyses.  Additionally, the Muir Milach  offloaded camp supplies and equipment on Ugamak Island for scientists conducting behavioral observations and brand sightings during summer 2002.

By John Sease.


Aerial Survey of Western Stock of Steller Sea Lions in the Gulf of Alaska and Aleutian Islands

The NMML conducted the biennial aerial survey for nonpup Steller sea lions in Alaska during 14-25 June 2002.  The survey covered approximately 280 western stock rookery and haul-out sites from Cape St. Elias (144E30’W) to Attu Island in the western Aleutian Islands (172E30’E).  The survey protocol was the same as for previous surveys - sites were photographed for later analysis in the laboratory.  The aircraft was a turbine-powered McKinnon Goose under contract from AeroPlanes, Inc., of Hillsboro, Oregon.  Final results of the survey will be available after analysis of the imagery during July and August.  Results from these June aerial surveys form the backbone of population trend analyses for Steller sea lions.

The 2002 survey included several new twists.  We experimented with a high-resolution digital camera as a possible alternative to the standard film imagery.  Additional back-up imagery was taken with digital video camera.  The NMML survey schedule also was coordinated with a second aircraft, chartered by NMFS Southwest Fisheries Science Center (SWFSC), in La Jolla, California.  The SWFSC survey uses medium format (5-inch) vertical photography, which produces high-quality imagery, but weather and terrain, particularly in the Aleutian Islands, can preclude surveying for days at a time.  It is possible to count newborn pups from the vertical images, so the survey window is more than a week later than for the NMML nonpup surveys.  Both the NMML and SWFSC surveys performed replicate surveys at selected sites in the Unimak Pass and Kodiak regions, which should provide us with a means to compare the two methods.

By John Sease.


Field Camps for Steller Sea Lion Studies in the Gulf of Alaska and Aleutian Islands

The NMML is operating three field camps to collect daily count, demographic, and brand resight data beginning late May through late July 2002. The camp on Marmot Island, approximately 30 miles north of Kodiak, has been operated most summers since 1991.  Newer camps are on Fish Island (near Prince William Sound) and on Ugamak Island (in Unimak Pass, eastern Aleutian Islands), where ADF&G and NMML have operated field camps in the past.  

By John Sease.


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