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Auke Bay Laboratories (ABL)

AFSC Quarterly
Research Reports
Oct-Nov-Dec 2007
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REFM Reports
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Marine Ecology & Stock Assessment Program

Groundfish Stock Assessments

This quarter, scientists from ABL's Marine Ecology and Stock Assessment (MESA) Program completed major stock assessments for eight species or species groups of Alaska groundfish: Gulf of Alaska Pacific ocean perch, northern rockfish, rougheye rockfish, pelagic shelf rockfish, shortraker rockfish, and other slope rockfish; Bering Sea/Aleutian Islands sharks; and Gulf of Alaska and Bering Sea/Aleutian Islands sablefish.

Stock Assessment and Fishery Evaluation (SAFE) reports were prepared for each assessment, and results were presented to the North Pacific Fishery Management Council's groundfish plan teams in November and also reviewed by the Council's Scientific and Statistical Committee in December. The Council used these assessments as the primary source for determining catch quotas (levels of Total Allowable Catch) for these species in 2008.

For detailed information about these assessments, see the Status of Stocks and Multispecies Assessment Program report in the Resource Ecology and Fishery Management (REFM) Division section of this publication.

By Dave Clausen

2007 Sablefish Longline Survey

The AFSC has conducted an annual longline survey of sablefish and other groundfish in Alaska from 1987 to 2007. The survey is a joint effort involving two divisions of the AFSC: ABL and the Resource Assessment and Conservation Engineering (RACE) Division. The survey replicates as closely as practical the Japan-U.S. cooperative longline survey conducted from 1978 to 1994 and also samples gullies not sampled during the cooperative longline survey. In 2007, the twenty-ninth annual longline survey of the upper continental slope of the Gulf of Alaska and eastern Bering Sea was conducted. One hundred-fifty-two longline hauls (sets) were completed between 2 June and 1 September 2007 by the chartered fishing vessel Ocean Prowler. Sixteen km of groundline were set each day, containing 7,200 hooks baited with squid.

Sablefish (Anoplopoma fimbria) was the most frequently caught species, followed by giant grenadier (Albatrossia pectoralis), arrowtooth flounder (Atheresthes stomias), shortspine thornyhead (Sebastolobus alascanus), and Pacific cod (Gadus macrocephalus). A total of 79,461 sablefish were caught during the survey. Sablefish, shortspine thornyhead, Greenland turbot (Reinhardtius hippoglossoides), spiny dogfish shark (Squalus acanthias), and lingcod (Ophiodon elongatus), were tagged and released during the survey. Length-weight data and otoliths were collected from approximately 2,219 sablefish. Killer whales (Orcinus orca) took fish from the longline at seven stations in the Bering Sea and five stations in the western Gulf of Alaska. For the first time during the survey time series, killer whales also took catch from a station in the central Gulf of Alaska. Geographically, this is the farthest east the survey has ever recorded killer whale depredation. Sperm whales (Physeter macrocephalus) were often present during haulback and were observed depredating on the longline at 11 stations in the eastern Gulf and 2 stations in the central Gulf of Alaska.

Several special projects were conducted during the 2007 longline survey. An AFSC intern from the University of Washington participated on a survey leg collecting coral specimens for identification and preservation. A seabird occurrence study, conducted for the sixth year, helps to address where and when certain seabird species occur in Alaska waters. Spiny dogfish and lingcod were tagged with archival temperature/depth tags, and sleeper sharks were tagged with satellite tags. Genetic samples and whole specimens of sablefish were collected in the Bering Sea and eastern Gulf of Alaska for population structure analysis. A grenadier study was conducted throughout the survey to examine potential morphology differences between big eye and small eye giant grenadier.

Photographs of sperm whales observed during the survey were taken for contribution to the Southeast Alaska Sperm Whale Avoidance Project (SEASWAP) sperm whale catalog. A marine mammal observer was on board during the fifth survey leg in the Gulf of Alaska to collect photo identification of sperm whales, record dive behavior observations, and collect biopsy samples for genetic and fatty acid analysis. Sperm whales interacting with the survey vessel near Sitka were also tagged with satellite tags in a cooperative project with SEASWAP. Finally, a 2-day gear experiment was conducted near Yakutat to compare the catching efficiency of standard survey gear to autoline gear.

By Chris Lunsford

Sablefish Tag Program

The National Marine Fisheries Service (NMFS) has conducted a sablefish tagging program in Alaska for more than 30 years; ABL has been tagging sablefish in Alaska since 1982. ABL has also administered the Alaska sablefish tag database since 1995. In 2007, tags were recovered from 524 sablefish, including 18 fish tagged as juveniles, 7 fish tagged with electronic archival tags, and 499 tagged with external Floy anchor tags. Canadian recoveries of U.S. tags (not yet received) plus late U.S. returns will likely bring the total sablefish tag recoveries for 2007 close to the 5-year average of 602 tags.

Tags from shortspine thornyheads, Greenland turbot, and Pacific sleeper sharks are also maintained in the sablefish tag database. Eight thornyhead, two turbot, and two sleeper shark tags were recovered in 2007; the turbot tags were both electronic archival tags. The archival tags record data on depth of the fish and on water temperature for up to 11 years, depending on the frequency of observations. Besides adult sablefish (603) and Greenland turbot (156), archival tags have been implanted in juvenile sablefish (406), shortspine thornyheads (203), Pacific sleeper sharks (135), spiny dogfish (166), and lingcod (41) in recent years. To date, archival tags have been recovered from 104 adult sablefish, 10 turbot, one sleeper shark, and one spiny dogfish.

Releases in 2007 included 3,804 adult sablefish, 681 shortspine thornyheads, 82 turbot (including 38 with archival tags), 41 lingcod (all archival), 67 spiny dogfish (all archival), and 161 juvenile sablefish (99 archival).

Two more sablefish released on seamounts in 1999 and 2000 were recovered in 2007, bringing the total of seamount to continental slope recoveries to 24. All but one of the 22 tags with known recovery data have been recovered west of their release position.

By Nancy Maloney

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