Research Document - 2001/135
Sablefish Stock Assessment for 2001 and Advice to Managers for 2002
By Haist, V., Hilborn, R., Wyeth, M.
The 2001 sablefish stock assessment addresses the objectives and questions specified by the DFO Groundfish Management Unit in their Request for Working Paper. The PSARC document includes summaries of the sablefish fishery and biological information, and provides analyses related to the fishery and tag dynamics.
As in previous sablefish assessments, the primary information we use to assess the stock is tagging data. The tagging analysis conducted for the current assessment uses only tag recoveries in the year following release to estimates exploitation rates and stock abundance. This analysis does not incorporate stock dynamics so we do not conduct stock projections.
B.C. sablefish stock abundance declined through the early 1990's, and has been relatively stable since 1996. The estimated abundance trends from tagging analysis, commercial CPUE indices, and survey CPUE indices are consistent. We believe the sablefish stock abundance is currently low and stable.
Estimated exploitation rates, in the range of 10-13% in recent years, are at the high end of the range we recommend for the sablefish stock. However, we believe that our estimates are biased high due to the disproportionate release of tagged fish in areas and depth zones of major commercial fishing effort, rather than randomly through the population. Sablefish survey data, including addition sets conducted during the 2000 survey in the 600-800 fm depth range, indicate fairly high fish density at depths greater than 450 fm where only a small fraction of tag releases and fishery effort occurs.
We estimate that approximately 30% of sablefish tagged off the Queen Charlotte Islands move to Alaskan waters. However, on the basis of analyses conducted to date, we are not in a position to provide specific advice regarding management of northern B.C. sablefish.
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