Fraser River Sockeye Fisheries and Fisheries Management - Cohen ...

test fisheries are analyzed in-season to determine the stock composition of harvest andescapements. Daily escapements of sockeye from marine fisheries are estimated in theFraser River at Mission using hydroacoustic techniques.The historical record (1997-2009) of the daily run size estimates for each run-timinggroup, as approved by the Fraser Panel, were evaluated for reliability and timeliness ofin-season reporting. These in-season estimates are compared to the final post-seasonestimates for each run-timing group. The methods used to derive the final post-seasonrun size estimate are described later in the report. We used daily plots of median percenterror (MPE) as a measure of accuracy, median absolute percent error (MAPE) to quantifyprecision, and R 2 as an indicator of reliability. The accuracy of in-season run sizeestimates tend to be biased high (i.e., forecasts larger than runs) with low precision (25-78% error) early in the migration period for Early Stuart and Summer-run sockeye but thebias and error is rapidly reduced to less than 20% as the run-timing approaches theirtypical halfway points and less than 7% as the runs near their end. The in-seasonforecasts for Early Summer and Late-run groups tend to be more accurate throughouttheir respective migration periods and precision remains in the range of 10-25% for mostof the run. In general, these statistics suggest that the in-season forecasts have beensufficiently accurate, precise and timely to make the management decisions needed toachieve the harvest rate goals defined for each of the four run-timing groups.In-season Monitoring MethodsThe following contains brief descriptions of the in-season run size estimation modelsused prior to 1995, adapted from PSC (1995):Commercial Purse Seine ModelsPrior to 1995, weekly catch and CPUE for purse seine fisheries in Juan de Fuca andJohnstone Straits was the major source of in-season run size information for Frasersockeye. These weekly catch and CPUE estimates were compared to total post-seasonreturns (using regression analysis) to define relationships that could be used in-season toforecast abundance. In these fishing areas, especially Johnstone Strait, sockeye areconfined to relatively narrow migration routes and are highly vulnerable to purse seinefisheries. Travel time between these fishing areas and the Fraser River at Mission istypically 5-7 days for Summer-run sockeye. Catch information from fisheries early in theweek are generally used by the Fraser Panel to formulate plans for the following week.81