This data set contains measurements of midwater walleye pollock biomass during annual or biennial acoustic-trawl surveys conducted by the Midwater Assessment and Conservation Engineering (MACE) Program, Resource Assessment and Conservation Engineering (RACE) Division, of the National Oceanic and Atmospheric Administration - National Marine Fisheries Service (NOAA-NMFS) Alaska Fisheries Science Center (AFSC). The survey was conducted from 09 June 2009 through 07 August 2009 using the NOAA Ship Oscar Dyson.

Midwater and bottom trawling was used to determine the species and length frequency composition of detected aggregations of fish. Pollock biomass (kg) was computed by applying length-specific target strength values and a length-weight relationship to 38 kHz backscatter data classified as pollock. The summary data set submitted here includes pollock biomass values summed between 16 m below the sea surface and 3 m above the seafloor within a rectangle with a north-south distance of 0.5 nmi (averaging distance along the survey transect) and an east-west distance of 20 nmi (interpolation distance 10 nmi to either side of the survey transect).