Science Advisory Report 2009/022
Pre-season run size forecasts for Fraser river sockeye and pink salmon in 2009
Summary
- The 2009 forecast of sockeye returns at the 50% probability level for all 19 stocks plus miscellaneous stocks is 10.6 million fish (255,000 Early Stuart, 739,000 Early Summer, and 8.7 million Summer and 907,000 Late).
- This 50% probability level return forecast (10.2 million excluding miscellaneous stocks) is below the long-term average for this cycle of 13 million fish (1980-2005). The Summer Run return forecast (48% Chilko 41% Quesnel) accounts for 82% of the total forecast. Of the total forecast, Late Run stocks comprise 9%, Early Summer Run stocks 7% and the Early Stuart Run stock comprise 2%.
- The 2009 forecast of pink salmon returns is 17.5 million (50% probability level).
- Forecasts are associated with relatively high uncertainty, consistent with previous Fraser sockeye forecast PSARC reviews (Cass et al. 2006) and recent research on coast-wide salmon stocks (Haeseker et al. 2007 & 2008).
- For adult sockeye returning in 2009, ocean conditions in their juvenile outmigration period (spring/summer 2007) were good for most physical (sea surface temperatures, upwelling, spring transition) and biological (zooplankton species composition abundance) indicators. This was an improvement over the transitional year in 2006 and the poor year in 2005 associated with reduced ocean survival and relatively poor returns in 2007 and 2008 for BC salmon stocks. Given the positive ocean productivity signals in 2007 relative to 2006 (transitional between poor and good) 2005 (poor), emphasis on median probability levels (50%) is recommended for 2009 sockeye return forecasts with the exception of Early Stuart.
- The forecasts for the Early Stuart power model at the 75% probability level for the past five years were closer to true returns compared to forecasts at the 50% probability level.
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