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Status of Stocks and Multispecies Assessments Program -
Fisheries Interaction Team

Atka Mackerel Tagging Studies

Atka mackerel represent one of the largest groundfish biomasses in the Aleutian archipelago, with current estimates of exploitable biomass in excess of 500,000 tons.  They occur in dense aggregations in the Aleutian island passes and  prefer habitat with strong currents.  Atka mackerel have been observed at great densities and are extremely patchily distributed in space and time.

In order to prevent possible prey shortage for the Steller sea lions, the National Marine Fisheries Service (NMFS) established 20nm no trawl zones around six sea lion rookeries in the eastern Aleutians in 1991.  In 1998, further efforts were made to spread out fishing effort temporally as well as spatially.  Instead of one season per year for Atka mackerel, an A and a B season were mandated and more quota was assigned to be caught outside of critical habitat.  These restrictions affected the fishery severely and the question arose as to the efficacy of the no trawl zones and the impact of the fishery on Atka mackerel.  In order to measure the impact, it is necessary to estimate small scale Atka mackerel abundance and potential changes in behavior or movement of Atka mackerel that could be attributed to the fishery.  The goal of this project is to use tagging methods to estimate local abundance and small scale movement of Atka mackerel around Steller sea lion rookeries and to examine potential fishery effects on Atka mackerel movement and abundance. 

A feasibility study was conducted in 1999 at Seguam Pass.  In summer 2000, approximately 8000 tagged Atka mackerel were released in Seguam Pass, and in 2001 approximately 1000 were released during a truncated cruise.  In June-July 2002, ~ 21,000 fish were tagged in the Seguam Pass area, and ~ 14,520 were tagged near Tanaga Pass.   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. 

The tagging model used was an integrated model using maximum likelihood to estimate all parameters simultaneously.  There were four components of the model including expected tag recoveries, tag loss, tag survival, and tag reporting.

Results to date suggest that there is relatively little movement of Atka mackerel from inside to outside the trawl exclusion zones, indicating that trawl exclusion zones are effective at protecting Atka mackerel near Steller sea lion rookeries around Seguam and Tanaga Passes.  Caution should be used in applying these results to other areas, each with resident Atka mackerel populations and fisheries of different size and distribution.  To examine geographical variation in movement and local abundance, FIT scientists will begin a parallel tag release-recovery study in third study area in the western Aleutians in 2003. 

Contact

For more details on the results summarized above, see the documents below or contact Susanne McDermott at susanne.mcdermott@noaa.gov or 1-206-526-4417


Current Issues

Documents

Cruise Report F/T Seafisher Cruise 200601 October 11 November 1, 2006 (PDF). Project Title: Atka Mackerel Tag Recovery Kiska Island and Seguam Pass, Aleutian Islands Alaska

Cruise Report F/V Pacific Explorer Cruise 200601 July 8 - July 21, 2006 (PDF). Project Title: Atka mackerel tag and release, Kiska and Seguam Islands, Aleutian Islands, Alaska


The Fishery Interaction Team: Investigating the potential impacts of commercial fishing on the foraging success of endangered Steller sea lions.  Alaska Fisheries Science Center Quarterly Report. April-May-June 2002

AFSC Quarterly Report: Atka Mackerel Tagging (July-September 2003)

Cruise Report, F/T Seafisher Cruise, SE200301 October 5 - 31, 2003 (PDF). Project Title: Atka mackerel tag recovery Amchitka Island and Seguam Pass, Aleutian Islands Alaska

Cruise Report, F/V Pacific Explorer Cruise 200301 (PDF) (12-26 July 2003)

Cruise Report, F/T Seafisher Cruises, SE200201 August 23-28, 2002 and  SE200202 September 30 - October 12, 2002 (PDF). Project Title: Atka mackerel tag recovery Seguam and Tanaga Passes, Aleutian Islands Alaska

Cruise Report, F/V Pacific Explorer Cruise 200201 June 10 - July 9, 2002 (PDF). Project Title: Atka mackerel tag and release Seguam and Tanaga Passes, Aleutian Islands Alaska.

Presentations

K. Rand and S. McDermott.  Seasonal changes in Atka mackerel sex ratios in Seguam and Tanaga Passes during 2002 (PowerPoint).  Marine Science for the Northeast Pacific: Science for resource-dependent communities,  January 13-17, 2003, Anchorage Alaska













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