Pacific Salmon Hatchery Review: weight and timing matter

Hatcheries were introduced in British Columbia in 1972 to help enhance salmon populations and conserve species at risk. Today B.C. hatcheries release approximately 300 million juvenile Pacific salmon each year.

While hatcheries can support healthy salmon populations, they can also have negative impacts on wild salmon, including effects on the genetics of wild populations, overharvesting of wild salmon that travel alongside hatchery fish, and competition for food and habitat. As hatcheries endeavour to provide a solution to address dwindling salmon populations in B.C., it’s imperative that we evaluate their effectiveness and find consistent methods to help improve survival rates.

The Pacific Salmon Foundation has completed the first comprehensive review of hatchery release strategies in B.C. The review considered all releases and recoveries of coded wire tagged Chinook and coho in the province since 1972, as well as specific release experiments run by the Salmonid Enhancement Program (SEP) over the last 20 years. In doing so, we were able to explore the relationships between release strategies and salmon survival and gain a better understanding of what works where.

What we learned: there is room for improvement in release strategies to help maximize survival. The size-at-release and time-of-release can make a difference. Results vary, but generally speaking, releasing fish at larger sizes and releasing Chinook earlier and coho later than they have been historically will likely result in higher survival rates.

“Both hatchery and wild salmon survival depend on the conditions they face as juveniles, so release strategies, such as the timing and size of the fish, matter,” said PSF biologist Sam James, who has a master’s degree in Oceanography from the University of British Columbia.

“However, there is no one-size-fits-all solution. Given that salmon populations in B.C. differ in genetics, habitats, and environmental exposures, salmon enhancement strategies need an equally diversified approach.”

Chum eggs collected from spawning salmon at the Chehalis River Hatchery (photo: Mirko Diaz)

Raising young Pacific salmon in hatcheries for life in the wild is complex. There are more than 9,000 distinct populations of Pacific salmon in B.C., each carrying unique genetics and life histories. Coupled with differences in hatchery operations and conditions, there is no all-encompassing solution. While PSF’s report provides hatchery-specific information for managers to consider when planning hatchery releases in the future and identifies locations with the greatest opportunities for improvement, each hatchery is unique and what works best in one location may not work at another.

Additionally, environmental conditions are changing, so the way in which hatchery salmon are reared and released needs to be adaptive to change. To do this, a diverse set of solutions accounting for these unique factors and changing conditions must be explored to optimize hatchery effectiveness. This will require long-term experiments, routine data collection and analysis, and increased monitoring at data-poor areas.

PSF’s multi-year Hatchery Effectiveness Review study aims to support hatchery managers as they navigate the complex relationships between release strategies and optimal salmon survival. The results from this stage indicate that additional release-strategy research and investment are necessary.

This is the second phase of PSF’s Hatchery Effectiveness Review. The third phase, currently underway, examines the effectiveness of hatcheries and their impacts on wild salmon.

This review was funded by the BC Salmon Restoration and Innovation Fund in 2019 and will run until the fall of 2022.