Science Advisory Report  2012/037

2011 Marine Survival Forecast of Southern British Columbia coho

Summary

• The southern BC coho assessment provides estimates of marine survival in 2010 and forecasts for 2011 for coho salmon stocks originating from South-west Vancouver Island, Georgia Basin – East, Georgia Basin – West, and the Lower Fraser.  For the Interior Fraser River Management Units, total 2010 spawning escapement and 2011 pre-season abundance is provided.  For the Johnstone Strait/Mainland Inlets Management Unit the summed 2010 spawning escapement from selected rivers and 2011 pre-season abundance is provided.
• Coho marine survival and abundance continues to remain low (less than 3%) for most southern BC coho stocks compared to the early 1970’s (15-20%).  Of particular note, the 2011 Interior Fraser River Interior and Thompson Aggregates are forecasted to decline in abundance in 2011.
• In light of the abundance trend, coupled with the continuing low marine survival rates of southern BC coho stocks, the forecast of marine survival and abundance should be characterized as extremely low, with except possibly for the west coast of Vancouver Island.
• The 2010 marine survival for West Coast indicator stocks, Robertson Creek (enhanced) and Carnation Creek (wild) were assessed at 3.3% and 1.0%, respectively.  The 2011 marine survivals, based on favourable survival conditions and using newer, but not reviewed growth model, is forecast to increase over the observed values from the previous year.
• The last full assessment of southern BC coho was reviewed and endorsed through CSAS in 2004, with subsequent assessments presented in the form of a Science Advisory Report using the approved methodology.  A full review of the assessment (forecast) methodology is recommended for future assessments to account for the addition/loss of indicator streams, change in enumeration methodology and model development that has occurred since 2004.
• Monitoring programs for coded-wire tagged, adipose fin clipped coho must be maintained or strengthened to continue to monitor southern B.C. coho populations.

This Science Advisory Report is from the June 27-28, 2011 Regional Advisory Meeting on the Synoptic Assessment Framework for Assessing Conservation Unit Status for Pacific Salmon; and 2011 Marine Survival Forecast of Southern BC Coho.  Additional publications from this process will be posted as they become available on the DFO Science Advisory Schedule.

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