Science Advisory Report 2010/056

Assessment of Cultus Lake Sockeye Salmon in British Columbia in 2009 and Evaluation of Recent Recovery Activities

Summary

• The abundance of adult sockeye salmon (Oncorhynchus nerka) returning to Cultus Lake has been monitored since 1921, and has been slowly declining since the 1970s. The recent generational (4-year) average is about 1,000 spawners, 5% of historical values.
• The decline appears to have been halted but the population has not met any of the recovery objectives set by the Cultus Sockeye Recovery Team, nor a lower benchmark proposed under the Wild Salmon Policy.
• Poor survival after smolts leave Cultus Lake is a major contributor to the recent status of the population.
• Recovery actions include reductions in harvest, predator control in Cultus Lake, and a captive broodstock/supplementation program.
• Concerns over Cultus Lake sockeye salmon have resulted in the 2000-2009 harvest rates being reduced to an average of 20% for the late-run complex of stocks.
• The removal of predators from the lake has coincided with an increase in the in-lake survival of juvenile sockeye salmon.
• Hatchery fry releases to the lake have resulted in increasing numbers of returning hatchery adults. The majority of adult sockeye that returned to Cultus Lake in 2008 and 2009 were hatchery-origin fish.
• The reproductive success of hatchery fish in the wild is unknown and the apparent failure of the 2008 brood, which consisted of >90% hatchery fish, is cause for concern.
• The prospects for the Cultus Lake sockeye population are highly uncertain as they are tied to future trends in smolt-recruit survival.
• Recovery actions should be considered experimental and need to be monitored carefully and managed adaptively.

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