Figure 2. Management areas (numbered), survey subareas (colored), and critical habitat zones for the eastern Aleutian Islands.
A hot topic for the National Marine Fisheries Service (NMFS) in Alaska over the past several years has been the ongoing Endangered Species Act Section 7 consultation Biological Opinion on the potential effects of the groundfish fisheries on the endangered western stock of Steller sea lions (Eumetopias jubatus). The most recent consultation concerns fishing in the Aleutian Islands, which was restricted after the 2010 Biological Opinion. The NMFS Alaska Regional office prepared a draft environmental impact statement (EIS) in 2013 and is in the process of preparing both the final EIS and a new Biological Opinion on this issue in 2014. Center staff from several divisions are active in research relating to Steller sea lions and have contributed support and assistance in the preparation of both documents during this past year.
Researchers from the AFSC Fisheries Interaction Team (FIT) met with marine mammal researchers and NMFS regional staff several times during 2013 to determine what data sources and research results or analyses could be used to support the 2014 Biological Opinion. The scientists discussed how previous analyses could be improved, and which data were available to describe dynamics in the Aleutian Islands. In particular, researchers looked for ways to use existing data at smaller spatial scales than the entire management region, to determine if correlations occurred between sea lion population trends and groundfish abundance or harvest in smaller areas within the Aleutians.
After careful review and consultation with the AFSC's RACE (survey) Division, we concluded that groundfish trawl survey data could be summarized at the spatial scale of the survey subareas, but that analysis at any finer spatial scale would not be scientifically defensible. The trawl survey divides the Aleutians into depth intervals (0-100 m, 100-200 m, 200-300 m, 300-500 m) and into spatial subareas defined by ocean basin and latitude, dividing the three regulatory areas of the Aleutians (statistical reporting areas 541, 542, and 543) into 10 subareas (Fig. 2). Our FIT researchers assembled a white paper summarizing existing trawl survey biomass estimates and fisheries observer data by these subareas, and looking for any evidence of trends over time (1991 – 2012), indications of seasonal differences in groundfish abundance, or spatial shifts in species composition of the groundfish most prevalent in sea lion diets. Reproductive seasons of groundfish prey species were also summarized into a combined table, as fish prey are often of particularly high nutritional value during spawning seasons.
The goal of these efforts was to collate and summarize existing data, publications, and recent research to describe the spatial and temporal distribution of groundfish in the Aleutian Islands, so that the authors of the 2014 Biological Opinion would have a clear picture of the Steller sea lion prey resources both inside and outside of areas designated as critical habitat. The resulting white paper and several analyses provided by the National Marine Mammal Lab have been made public on the NMFS Alaska Protected Resource website.
