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Marine Ecology & Stock Assessment Program

Sablefish Maturity Cruise Completed

Katy Echave
Figure 1.  Auke Bay Lab scientist Katy Echave at the sampling station aboard the fishing vessel Gold Rush during the sablefish maturity cruise near Kodiak, Alaska, December 2011.
 
 

AFSC biologists Katy Echave (Fig. 1) and Jim Stark completed a 10-day cruise in December off Kodiak Island, Alaska, aboard the chartered fishing vessel Gold Rush as part of a special study to better define the reproductive patterns of sablefish in Alaska waters.

The new study, a joint effort between ABL and the RACE Division, is designed to provide important, accurate estimates of sablefish age and length at maturity, a critical component of the stock management models used to set the overfishing limit and maximum sustainable yield.

Managed by the North Pacific Fishery Management Council, the sablefish population in Alaska waters is healthy and above biomass limits. Continuing this sustainable fishery into the future will benefit consumers, fishermen, processors, shipyards, and the fishing community.

More information on the project is available in this issue in the RACE Division's Groundfish Program report.

By Julie Speegle


2011 Sablefish Longline Survey

The AFSC has conducted an annual longline survey of sablefish and other groundfish in Alaska from 1987 to 2011. The survey is a joint effort involving the AFSC's Auke Bay Laboratories (ABL) and Resource Assessment and Conservation Engineering (RACE) Division. It 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 2011, the thirty-third 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 during 25 May - 28 August 2011 by the chartered fishing vessel Ocean Prowler. Sixteen kilometers 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), Pacific cod (Gadus macrocephalus), shortspine thornyhead (Sebastolobus alascanus), and arrowtooth flounder (Atheresthes stomias). A total of 98,592 sablefish were caught in 2011, representing a substantial increase over the 2010 survey sablefish catch. Sablefish, shortspine thornyhead, Greenland turbot (Reinhardtius hippoglossoides), spiny dogfish (Squalus suckleyi), and lingcod (Ophiodon elongates) were tagged and released during the survey. Length-weight data and otoliths were collected from 2,532 sablefish.

Killer whales (Orcinus orca) took fish from the longline at seven stations in the Bering Sea region, five stations in the western Gulf of Alaska, and one station in the central Gulf of Alaska. This represents a slight increase in killer whale interactions in the Western Gulf compared to 2010 but a decrease in the Bering Sea. Sperm whales (Physeter macrocephalus) were often present during haul back and were observed depredating on the longline at nine stations in the East Yakutat/Southeast region, four stations in the West Yakutat region, and one station in the central Gulf of Alaska. These numbers represent an increase in sperm whale interactions over the previous year but are below the highest number of interactions seen in 2008.

Several special projects were conducted during the 2011 longline survey. Lingcod and spiny dogfish were tagged with archival temperature/depth tags in the West Yakutat and central Gulf of Alaska regions. Forty-five satellite pop-up tags were deployed on spiny dogfish throughout the Gulf of Alaska. Information from these tags will be used to investigate the movement patterns of spiny dogfish within and out of the Gulf of Alaska.

Additionally, genetic tissue and otoliths of giant grenadier were sampled to see if geographic stock structure exists and to determine if three distinct otoliths shapes identified in previous work correspond to different subspecies or subpopulations. Finally, opportunistic photo identification of both sperm and killer whales were collected for use in whale identification projects.

By Chris Lunsford
 

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