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Data report: 2012 Aleutian Islands bottom trawl survey


The sixth biennial groundfish assessment survey of the Aleutian Islands region was conducted during the summer of 2012 by the Alaska Fisheries Science Center’s (AFSC) Resource Assessment and Conservation Engineering (RACE) Division. This effort constitutes the twelfth in the full series dating from 1980. The survey area covered the continental shelf and upper continental slope to 500 m in the Aleutian Archipelago from Islands of Four Mountains (170° W long.) to Stalemate Bank (170° E long.), including Petrel Bank and Petrel Spur (180° long.), and the northern side of the Aleutian Islands between Unimak Pass (165° W long.) and the Islands of Four Mountains.

The survey was conducted aboard two chartered trawlers, the F/V Ocean Explorer and F/V Sea Storm. Samples were collected successfully at 420 survey stations using standard RACE Division Poly Nor’Eastern high-opening bottom trawl nets with rubber bobbin roller gear. The primary survey objectives were to define the distribution and estimate the relative abundance of principal groundfish and commercially or ecologically important invertebrate species that inhabit the Aleutian marine habitat and to collect data to define biological parameters useful to fisheries researchers and managers such as growth rates; length-weight relationships; feeding habits; and size, sex, and age compositions. Pacific ocean perch or POP (Sebastes alutus) were by far the most abundant species with an estimated biomass of 902,399 metric tons (t). Northern rockfish (Sebastes polyspinis) and Atka mackerel (Pleurogrammus monopterygius) were also abundant with estimated biomasses of 285,164 and 276,877 t, respectively.

Catches of POP were large throughout the survey area at intermediate depths. Northern rock sole were the most abundant flatfish species although they were rarely encountered in the southern Bering Sea. Arrowtooth flounder (Atheresthes stomias) were almost as abundant and were more ubiquitous. The skate assemblage was comprised of three skate species, whiteblotched (Bathyraja maculata), leopard (B. panthera) and Aleutian (B. aleutica), with a wide diversity of species captured in the eastern portion of the survey area. Survey results are presented as estimates of catch per unit of effort and biomass, species distribution and relative abundance, population size composition, and length-weight relationships for commercially important species and for others of biological interest.

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