Research Document - 2000/159
A Preliminary Review of A New Model Based On Test Fishing Data Analysis to Measure Abundance Of Returning Chum Stocks To The Fraser River.
By W.J. Gazey, and R.V. Palermo
Abstract
The test-fishery has operated at Albion on the Fraser River since 1978 to provide the means for an index of chum salmon abundance (escapement) within a season. Recent degradation of the accuracy and consistency of escapement estimates has seriously undermined the potential to evaluate clockwork management for the Fraser River chum salmon (PSARC paper S99-20, Ryall et al.). To address this problem the cumulative catch-per-unit-effort (CPUE) was calculated to account for saturation, depletion in the second set and interpolation for missing sampling days. In addition, the test-fishery data were cast into a Bayesian framework that incorporated preseason knowledge of run size and migration timing, within season information on migration timing and a predictive regression to calibrate run size to the historical record. Based on a retrospective analysis of 1979-1998 data, the Bayesian procedure was judged to be superior to the classical test fisheries approach of using a simple predictive regression of cumulative CPUE on run size. However, the predictive ability of the either model was seriously compromised by the reliability of escapement enumeration (end of season minimal residual standard deviation).
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