Small-scale Atka mackerel population abundance and movement in the western Aleutian Islands, an area of continuing Steller sea lion decline

Groundfish stocks in Alaska are managed at large scales, however important ecological interactions, such as predation, spawning and habitat selection occur on local scales.

mock Dead Fish from ingesting plastics

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. Our project will assess 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 will accomplish this goal through tagging, releasing and recovering Atka mackerel at several sites inside and outside protected areas. These data will be analyzed with our published mark-recapture model to estimate local abundance and movement rates. We will also collect egg masses and identify spawning fish and will thus improve identification of Atka mackerel spawning habitat and our understanding of fish movement with relation to spawning habitat.

Study documents