AUKE BAY LABORATORY (ABL) (cont.)

Groundfish Assessment Program

Pacific Sleeper Shark Electronic Archival and Acoustic Tagging in Upper Chatham Strait, Southeast Alaska

Little is known about the life history or ecological role of Pacific sleeper sharks (Somniosus pacificus) in the North Pacific Ocean. In an ongoing study of this species in Southeast Alaska, ABL scientists tagged 45 sleeper sharks in upper Chatham Strait with electronic archival tags in 2003, and 23 sharks with acoustic transmitting tags in May 2004. Temperature, depth, and location data from the tags aid in identifying Pacific sleeper shark distribution and habitat utilization in Southeast Alaska and the potential for interactions between Pacific sleeper sharks and other species in this region.

The electronic archival tags were externally mounted, and record temperature and depth every 10 seconds for up to 5 years; data is saved in memory for up to 10 years. Because Pacific sleeper sharks are occasionally captured as bycatch in commercial longline fisheries for halibut and sablefish (blackcod), ABL is offering a $200 reward for the return of electronic archival tags from the commercial fishery. The ADF&G and commercial longline fishing organizations in Southeast Alaska have been alerted about the reward program.

The acoustic tags were surgically implanted, and transmit location and depth every 10 seconds for up to 1 year. Data from the acoustic tags is recovered with hydrophones deployed from charter vessels. In June 2004, 13 previously tagged Pacific sleeper sharks were located acoustically and tracked in upper Chatham Strait surveys.

By Dean Courtney


2004 Sablefish Longline Survey

The AFSC has conducted an annual longline survey of sablefish and other groundfish off Alaska since 1987. The survey is a joint effort involving ABL and the RACE Division. Beginning in 1996, biennial sampling of the Aleutian Islands region and eastern Bering Sea was added to the survey.

The 2004 survey began on 1 June and will end on 1 September using the chartered fishing vessel Alaskan Leader. As of July, the survey has sampled the Aleutian Islands and the western Gulf of Alaska. The survey vessel will transit the Gulf of Alaska in early July and resume sampling near Ketchikan on 8 July, and will then move west until the survey concludes in Dutch Harbor. The vessel will be making port calls with changes of scientific personnel in Ketchikan, Yakutat, Cordova, and Kodiak.

Catches in the Aleutian Islands and western Gulf of Alaska have been strong and appear to be similar to catches from 2002 and 2003. Two pods of killer whales took fish from the longline at five stations in the western Gulf near Dutch Harbor, resulting in lower overall catches at those stations. Attempts to elude the whales were unsuccessful; killer whale depredation is common in this area each year.

Detailed analyses of the overall catch will be made following the conclusion of the survey. Abundance information, length frequencies, and age data collected during the survey will be incorporated into the sablefish, Greenland turbot, shortspine thornyhead, and rougheye rockfish assessments.

By Chris Lunsford


Sablefish Tag Rewards

The 13th annual sablefish tag prize drawing was held in May 2004. The drawing is an annual event that encourages reporting of tagged sablefish recoveries. Participants receive a baseball cap and a drawing ticket for each tag returned. A total of 578 tags recovered during 2003 were represented in this year’s drawing. Four cash prizes ($1,000, $500, and two $250) were awarded. The drawing winners included a Sitka fisherman, a Seward processor, a Colorado fisherman visiting Alaska, and a processor from a catcher-processor vessel.

As of July, five more sablefish archival tags have been turned in, bringing the total recoveries to 65 since the program started. Three $500 prizes and two $200 prizes were awarded for the latest recoveries. The archival tags provide a record of the water temperature and depth experienced by the fish over a 2-year period.

By Nancy Maloney


Completion of Southeast Alaska Steller Sea Lion Prey Study

Final sampling for the Southeast Alaska Steller sea lion prey study was concluded during the second quarter of 2004. The study duration was 3 years. ABL scientists J. J. Vollenweider and Lee Hulbert surveyed standard longline stations and collected samples for nutritional analysis aboard the chartered fishing vessel San Juan in Frederick Sound in May. Mike Sigler of ABL conducted three acoustic surveys of eulachon in Berners Bay aboard the chartered fishing vessel Williwaw during April. The Berners Bay trips were part of a cooperative study with University of British Columbia researchers Mary-Anne Lea and Ben Wilson, who followed sea lions tagged with VHF and satellite depth tags. Now that all field sampling for this study has been completed, analyses and reporting are under way.

By Mike Sigler

AFSC Quarterly Research Reports Apr-June 2004