Potential effects of Spawning Enhancement on Wild Babine Sockeye: a Review

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Artificial propagation is an important tool for increasing the harvest of exploited fish, and restoring depressed wild populations. A spawning channel is one propagation technique often considered benign, yet its potential to adversely impact wild salmon has been poorly assessed. Given recent prompts by the Marine Stewardship Council and an independent science review panel to assess the potential effects of channel-enhanced fish on wild populations, my intention here is to review the relevant literature, and offer suggestions of key research questions aimed at addressing current knowledge gaps. Several negative ecological effects for wild stocks due to spawning channels are evident from Canada’s largest sockeye salmon (Oncorhynchus nerka) producing lake. Increased production of spawning channel fish since the 1970s has intermittently altered prey communities, and reduced the average weight of juveniles leaving the nursery lake. Marine survival rates decline with increasing numbers of emigrating juveniles. High harvest rates targeted at channel-produced salmon appears to have contributed to the decline of less productive stocks. Finally, pathogen transmission may be more likely to occur when channel-produced fish densities are high. Targeted research is required to fully evaluate the sustainability of wild and channel-produced salmon.

Note: this review consists of a narrative report, an annotated bibliography, and a summary of knowledge gaps.