Scup : Stock Assessment and Biological Reference Points for 2008

Scup 293 Executive Summary The current biomass reference point for scup relies on the index of Spawning Stock Biomass (SSB) from the NEFSC spring trawl survey. Previous reviews of the stock assessment have indicated that while this index may be the most reliable fishery independent index of scup SSB, it is subject to a relatively high degree of inter-annual variability that reduces its utility as an indicator of stock status. Managers, scientists, and other stakeholders indicated a desire for a more reliable way to monitor the status of scup and support the annual specification of fishery regulations. The December 2008 Northeast Data Poor Stocks Peer Review Panel accepted a revised stock assessment using a statistical catch at age model (ASAP) as the basis for biological reference points and status determination for scup. The new model of scup population dynamics and the recommended reference points represent a more stable approach for monitoring stock status and specifying annual fishery regulations, compared with the current single index-based model. The new model integrates a broad array of fishery and survey input data and should be less sensitive to inter-annual changes in any single data component than the current model. The Peer Review Panel recommended F 40% as the proxy for F MSY , and the corresponding SSB F40% as the proxy for SSB MSY. The F 40% proxy for F MSY = 0.177, the proxy estimate for SSB MSY = 92,044 mt, and the proxy estimate for MSY = 16,161 mt (13,134 mt of landings, 3,027 mt of discards). The stock biomass threshold of ½ SSB MSY = ½ SSB F40% = 46,022 mt = 101.461 million lbs. The 2007 SSB estimate of 119,343 mt is 30% above SSB MSY = 92,044 mt, indicating the stock was not overfished. The F 2007 estimate of 0.054 is 31% of F MSY = 0.177, indicating overfishing was not occurring. Total catch (landings plus discards) was 7,867 mt in 2007, about 49% of MSY. The revised status determination represents a significant change from the recent biomass status update conducted in July 2008, which indicated that the stock was overfished in 2007, although not experiencing overfishing. While the accepted long-term MSY estimate appears feasible given historical evidence from the fishery, managers may wish to take an adaptive approach to the specification of fishery quotas in the short-term. Total fishery landings over the last five years (2003-2007) have averaged …