Status of Stocks & Multispecies Assessment Program

Fisheries Interaction Team (FIT) Staff Conduct Successful Atka Mackerel Tag Recovery Cruise in the Aleutian Islands

Figure 2. Atka mackerel tag release and recovery locations, 2a. Seguam Pass, 2b. Tanaga Island, 2c. Petrel Bank.

The objective of our tag release-recovery studies is to determine the efficacy of trawl exclusion zones as a management tool to maintain prey abundance/availability for Steller sea lions at local scales.

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.

This study is an ongoing research effort. From 1999 to 2006, approximately 80,000 tagged fish were released during NMFS chartered tag release cruises near Seguam Pass, Tanaga Pass, Amchitka Island, and Kiska Island.

In May to June 2011 a cooperative venture between the North Pacific Fisheries Foundation and NMFS released approximately 8,500 tagged fish near the Seguam Pass area, 9,000 fish at Tanaga Pass, and 10,000 at Petrel Bank (Fig. 2).

This cruise had three objectives. The first objective was to recover the previously tagged fish in the open areas outside the trawl exclusion zones. Even though tags were released inside the closed areas, during the current recovery cruises in 2011, recoveries were not conducted inside the trawl exclusion zones to minimize potential negative impacts of Atka mackerel removal to the Steller sea lion prey fields inside the closed areas.

The second objective of the study was to use catch composition data from these tows to estimate relative abundance indexes (CPUEs) for all major fish and invertebrate species present in the study areas.

The third objective was to characterize Atka mackerel habitat and develop methods for estimating indices of abundance of SSL prey species with non-extractive methods such as camera tows.