Research Document - 2006/060

Pre-season run size forecasts for Fraser River sockeye for 2006

By Cass, A., M. Folkes, C. Parken, and C. Wood

Abstract

Pre-season abundance forecasts are used for pre-season planning and during in-season assessments of run size for fishery management. Forecasts are produced annually by Fisheries and Oceans Canada (DFO). Forecasts of sockeye returns typically are made using a variety of models depending on data availability. In this year’s assessment, a suite of biological and naïve models were assessed against standard performance measures. The biological models include models relating recruitment (and returns) to predictor variables (escapement, fry, smolts, and age-3 (jack) siblings in the case of Cultus Lake sockeye). We also investigate some environmental variables on model performance. These include Fraser River discharge, sea surface temperature (SST) data and the Pacific Decadal Oscillation index (PDO). Uncertainty in forecasts for 2006 is captured using Bayesian statistical inference. Nineteen stocks and four run timing groups were forecasted. Most of the forecasts are associated with large uncertainty. This is consistent with previous Fraser sockeye forecasts PSARC reviews and recent research on coast-wide salmon stocks ranging from Alaska to BC. Pre-season forecasts at the 50% probability level for all stocks totalled 17.4 million sockeye for 2006. By timing group, this includes 84,000 Early Stuart sockeye, 1.3 million Early Summer sockeye, 7.2 million Summer run and 8.8 million Late run sockeye.

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