Resource Ecology & Fisheries Management  (cont.)

Atka Mackerel Tag Recovery

The fishing vessel Seafisher was chartered 10-19 November 2001 for recovering tagged Atka mackerel in the Seguam Pass area of the Aleutian Islands, Alaska.  The cruise represents the third consecutive year of work by the AFSC on Atka mackerel in Seguam Pass and is part of an ongoing study to determine the efficacy of trawl exclusion zones to maintain prey availability for endangered Steller sea lions.  Trawl exclusion zones were established around sea lion rookeries as a precautionary measure to protect critical sea lion habitat, including local populations of prey such as Atka mackerel.  Localized fishing may affect Atka mackerel abundance and distribution near sea lion rookeries.  Tagging experiments are being used to estimate abundance and movement between areas open and closed to the Atka mackerel fishery.  Recovery of tagged fish is supplied by the fishery in the open area outside the trawl exclusion zone.  Recoveries in the closed area are provided by chartered recovery cruises such as the Seafisher cruise in November.

The primary objective of the charter was to examine 750 t of Atka mackerel collected from, in, and around the trawl exclusion zones at Seguam Pass for tags.  Standard fishery observer catch estimation, species composition, and Atka mackerel length sampling procedures were used.  In addition, the recovery rate of tags aboard the vessel was estimated.  This involved tagging twenty Atka mackerel on deck and placing them randomly into the catch of each haul.  Recovery of these “seeded” tagged fish enables calculation of a recovery rate of tagged fish within the factory which can then be applied to the tagged fish recovered from the ocean.  A total of ten Atka mackerel that had been tagged and released in previous AFSC cruises were found.  All of the fish had been tagged in 2001.  Several biological sampling projects were also carried out.  Atka mackerel otoliths were collected on nearly all of the 51 hauls.  In addition, stomachs from Atka mackerel, Pacific cod, halibut, and arrowtooth flounder were collected.  Finally, whole fish of a variety of species (Atka mackerel, northern rockfish, walleye pollock, rock sole and skates) were frozen for proximate analysis (caloric content).

By Libby Logerwell.

 
Resource Ecology and Ecosystem Modeling Program

Fish stomachs collected totaled 1,076 from the eastern Bering Sea and 254 from the Gulf of Alaska. Laboratory analysis was performed on 1,865 groundfish stomachs from the eastern Bering Sea, 1,304 from the Gulf of Alaska, and 627 from the Washington-Oregon-California region.  A total of 17 observers returned groundfish stomach samples during the quarter.

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AFSC Quarterly
Research Reports
Oct-Dec 2001