The Catch Accounting System (CAS) creates total catch estimates for the groundfish fisheries in the Bering Sea/Aleutian Islands and Gulf of Alaska. Each year, quotas are established in the CAS that match the annual harvest specification tables for federally managed groundfish fisheries off Alaska. The output of the CAS is the total amount of groundfish that is retained and the amount that is discarded at sea. In addition, the system creates estimates of the total amount of non-groundfish species -- both prohibited species and non-target species -- that are caught in the groundfish fisheries. Prohibited species catch (PSC) consists of salmon, halibut, and several species of crab. All the PSC species have economic value in non-groundfish fisheries and therefore cannot be retained in the groundfish fisheries. Non-target catch are species like coral, sponges, etc., and catch of these species needs to be calculated in order to evaluate the impact of the groundfish fisheries on the ecosystem.

The CAS uses a combination of industry reports and onboard observer information to provide an estimate of total catch and bycatch. Industry reported data consists of catch (landing reports) and processed product amounts (production reports), and these reports are electronically recorded and submitted to NMFS via eLandings. The observer data are collected by the Alaska Fisheries Science Center (AFSC) using a stratified sampling design. Other sources of information come from the Alaska Commercial Fisheries Entry Commission (CFEC), which issues permits and vessel licenses, and Vessel Monitoring Systems (VMS), which collect the position, time at a position, and course and speed of fishing vessels.