The Blend was the system used by the NMFS Alaska Regional Office to monitor groundfish catch from 1991 until 2002. The Blend system combined data from industry production reports and observer reports to make the best, comprehensive accounting of groundfish catch. These data were used to manage quotas for groundfish in the Gulf of Alaska, Bering Sea, and Aleutian Islands. The blend catch data were also used as the basis for computing estimates of prohibited species bycatch. Prohibited species include Pacific halibut, salmon, herring, and crabs. Blend data were used for numerous regional and national reports, fishery stock assessments, and analysis of fishery management plans. The Blend system used a combination of industry reports and observer data. For shoreside processors, Weekly Production Reports (WPR) submitted by industry were considered the best source of data for retained groundfish landings. All fish delivered to shoreside processors were weighed on scales, and these weights were used to account for retained catch. Observer data from catcher vessels provided the best data on at-sea discards of groundfish by vessels delivering to shoreside processors. Discard rates from these observer data were applied to the shoreside groundfish landings to estimate total at-sea discards from both observed and unobserved catcher vessels. For observed catcher/processors and motherships, the WPR and the Observer Reports recorded estimates of total catch (retained catch plus discards). If both reports were available, the Blend System selected one of them for incorporation into the catch database. If the vessel was unobserved, only the WPR was available. In 2003, the Catch Accounting Sytem was implemented and took advantage of industry reports at a more detailed level, especially from shoreside processors. The Blend system was based on weekly data from processors and was not capable of accounting for some management programs -- including cooperatives, sideboards, complex seasonal allocations, Harvest Limit Area quotas, and quotas assigned to vessels of a particular size class. The Catch Accounting System replaced the Blend as the tool used by the National Marine Fisheries Service to estimate total catch in the groundfish fisheries off Alaska.