Fishery Interaction and Availability of Atka Mackerel Prey for Steller Sea Lions: Results from a Local Abundance and Movement Study of Atka Mackerel

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Atka mackerel (Pleurogrammus monopterygius) are the most abundant commercially exploited groundfish in the Aleutian Islands, Alaska. They display a highly aggregated patchy distribution, centered around island passes and areas of high currents. Atka mackerel are demersal batch spawners with males guarding nests for up to six months of the year. Females aggregate in large schools near the spawning grounds, presumably to feed. Atka mackerel is the predominant prey of the endangered Steller sea lion in the Aleutian Islands. Trawl exclusion zones of 10 to 20 nm have been established around rookeries to protect Steller sea lion prey abundance. This study estimated the movement and local abundance of Atka mackerel with a mark recapture experiment using an integrated tagging model. Atka mackerel were tagged, released, and recovered from 2000 – 2006 in four local areas inside and outside of trawl exclusion zones in the Aleutian Islands. Population abundance was examined with respect to Steller sea lion prey energetic requirements within the trawl exclusion zones. Atka mackerel local movement patterns across these harvest boundaries was related to local fishing patterns and the interaction between fishery and prey abundance was examined.