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NOAA Technical Memorandum NMFS-AFSC-286

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Catch sampling and estimation in the federal groundfish fisheries off Alaska, 2015 edition


This report provides an update to the methodologies used by the National Marine Fisheries Service (NMFS) to estimate total catch in the Federal groundfish fisheries in waters off Alaska. The impetus for this update was a series of changes to the data collection and catch estimation methods, the most significant of which was a restructuring of the North Pacific Groundfish and Halibut Observer Program.

A combination of industry and observer information is used by NMFS to estimate total catch. Industry-reported data consists of catch and processed product amounts that are electronically recorded and submitted to NMFS. An extensive observer program provides at-sea information on total catch. The observer data are collected using a stratified hierarchical sample design where strata are defined through a combination of regulations and an annual deployment process. Within each stratum, a multi-stage sampling design is used to sample the species composition of the catch along with other catch components.

The Alaska catch accounting system (CAS) uses post-stratification procedures to combine the observer and industry information to create estimates of total catch. The CAS procedures changed to complement the sampling procedures established under the restructured observer program, including changes to post-stratification in the CAS and providing catch estimation on vessels retaining Pacific halibut (Hippoglossus stenolepis). In this report, we update the description of the CAS procedures and discuss continued evaluation of the estimation methods including developing uncertainty measures around point estimates of catch.

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