The Natural Regulation and Relevance of Wild and Hatchery Coho Salmon Production in the Strait of Georgia

The commercial and recreational fishery for Coho Salmon Oncorhynchus kisutch in the Strait of Georgia in the 1970s and 1980s that annually averaged 733,800 individuals declined in the 1990s and was closed in 1998. We observed that above a threshold, ocean carrying capacity is regulating production and not the number of juvenile Coho Salmon entering the Strait of Georgia. We show that a 52% reduction in releases of Coho Salmon from Canadian hatcheries from 2010-2018 did not change the average abundance of hatchery fish surviving through to September of their first ocean year. Our explanation that above a threshold number of smolts, ocean carrying capacity is regulating production rather than escapements is relevant to rebuilding efforts and the use of hatcheries. The results add to the accumulating evidence that production of Pacific salmon Oncorhynchus spp. is closely related to the capacity for rapid growth in the first months in coastal ecosystems.

Automated summary

The commercial and recreational fishery for Coho Salmon in the Strait of Georgia declined in the 1990s and was closed in 1998. It was observed that ocean carrying capacity seemed to regulate production more than the number of juvenile Coho Salmon. Even with a 52% reduction in releases of Coho Salmon from Canadian hatcheries from 2010-2018, the average abundance of hatchery fish surviving through to September of their first ocean year did not change.