Local Abundance and Movement of Atka Mackerel and Other Steller Sea Lion Prey in the Aleutian Islands

This study will examine local abundance and movement of Atka mackerel and other Steller sea lion prey species around rookeries and haulouts in the central Aleutian Islands.  Groundfish stocks in Alaska are managed at large scales, however important ecological interactions, such as predation, spawning and habitat selection occur on local scales.  Furthermore, commercial fishing is an activity with potential for localized effects.  Improved understanding of the local abundance and movement of fish is critical to understanding the potential for localized depletion by fishing.  In 2000 National Marine Fisheries Service concluded that the Alaska groundfish fishery posed a threat to the recovery of the endangered Steller sea lion population.  Protection measures were put in place, including Trawl Exclusion Zones in Critical Habitat around sea lion rookeries and haulouts.  The designation of these zones mitigates against the possibility that competition between fisheries and sea lions occurs at local scales.  Thus, advances in Alaska groundfish fisheries management with regard to their impacts on Steller sea lions require information on local abundance and movement of sea lion prey.  This study assessed the small-scale abundance, movement, and local exploitation rates of Atka mackerel, the dominant prey of sea lions in the Aleutian Islands, in relation to management boundaries such as Trawl Exclusion Zones.  We accomplished this goal through tagging, releasing and recovering Atka mackerel at several sites in the central Aleutian Islands in 2011.  In addition to tag release data, this study also examined the Catch per unit effort of other prey species such as Pacific Cod and Pollock and conducted camera transects close to the haul locations.  We will present preliminary results of tagging, CPUE estimates, and the camerawork and compare all three methods.