PSF researchers have completed a review of Pacific salmon hatcheries in British Columbia. The first of its kind since the mid-1990s, the review led to 15 reports and several recommendations to improve hatchery effectiveness and operations.
This story originally appeared in the Winter 2023 edition of Salmon Steward, the Pacific Salmon Foundation’s quarterly print magazine. The review was published in American Fisheries Society’s Fisheries Magazine in April 2024.
Under the DFO’s Salmonid Enhancement Program (SEP), B.C. hatcheries, spawning channels, and small community projects currently release approximately 250 million juvenile Pacific salmon per year. Surprisingly, this only accounts for a tiny fraction (around five per cent) of the five billion juveniles released across the North Pacific region, but it’s still a significant investment of capital and resources for Canada.
While hatcheries can produce abundant salmon, they can also have negative impacts on wild salmon. Scientists, First Nations, and anglers alike often pose the question: are B.C.’s hatcheries effective?
In a bid to find answers, PSF launched the Hatchery Effectiveness Review in 2019, led by Dr. Isobel Pearsall, director of PSF’s Marine Science Program, and Science Advisor Dr. Brian Riddell and SEP was very supportive of this work being undertaken.
The study was initially prompted by results from PSF’s Salish Sea Marine Survival Project, where researchers on Vancouver Island found that wild Chinook salmon survived at three times the rate of hatchery Chinook in the Cowichan River. The results warranted further investigation and a broader geographic focus.
“We’ve been releasing hatchery-produced fish for more than five decades, but it hasn’t translated to consistent and abundant salmon returns,” says Dr. Pearsall. “It became obvious that a comprehensive review of hatchery effectiveness was needed to guide future management decisions. In such a large and diverse program like SEP, there’s always room for improvement.”
When DFO unveiled SEP in 1977, it was an ambitious strategy that set out to restore salmon populations and double annual commercial catch by 2005. But the objectives set by SEP in the 1970s have shifted considerably in the wake of social, political, and environmental change over the years. Today, SEP operates 16 large-production hatcheries and seven spawning channels. It also supports many community-run, smaller-scale hatcheries, many of which regularly receive PSF grants.
PSF’s review focused on three main components associated with hatchery effectiveness in SEP: hatchery release strategies, wild and hatchery fish interactions, as well as genomics opportunities to study salmon. The review resulted in 15 reports, each available on our website.
In February 2023, PSF’s Hatchery Effectiveness Review published its first peer-reviewed study. PSF scientists assessed that SEP’s major hatcheries have productive release strategies that are resilient to extensive change in natural environmental conditions. They did this by analyzing data from DFO release experiments and from tagged Chinook and coho dating back to 1972.
“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,” says PSF biologist Sam James, who led the release strategy study.
However, depending on the facility and environmental factors encountered in any given year, results revealed that some SEP hatcheries might benefit from changes to ‘size-at-release’ and ‘time-of-release’ practices beyond those historically used.
James and her team analyzed 21 Chinook and 16 coho hatcheries. Data showed that for Chinook, survival rates increased for fish released earlier than most hatcheries’ historical averages. The opposite was true for coho, who were more likely to survive when released later than previous release dates. Based on results from these hatcheries, releasing fish at larger sizes and at different times could result in higher survival rates.
“However, there is no one-size-fits-all solution,” emphasizes James. “Given that salmon populations in B.C. differ in genetics, habitats, and environmental exposures, salmon enhancement strategies need an equally diversified approach.”
PSF’S FIVE KEY RECOMMENDATIONS:
The multi-generational impact of mixing hatchery and wild salmon is still poorly understood. To investigate this, researchers undertook several analyses, including assessing the contribution of Canadian hatcheries to fisheries and the ability for hatchery-reared salmon to rebuild natural populations. They also developed models to determine the influence hatchery releases have on local wild salmon and studied trends in the biological characteristics of B.C.’s Chinook salmon.
Unfortunately, analyses were limited by poor data, but researchers found SEP hatcheries have certainly contributed to harvests and are effective at producing juvenile fish.
However, they also demonstrated that SEP hatcheries to date have not been able to clearly prove that hatcheries contribute to rebuilding natural salmon production in the longer term. Science showed that traditional hatchery operations provide a ‘boost’ in the number of spawners during the period they are released, but over time, the boost reverts to a depressed spawning population. These findings are consistent with other studies in the United States and elsewhere.
“Our results indicate that short-term supplementation is seldom successful in restoring and sustaining natural populations,” says Dr. Brian Riddell. “But further research is needed to establish whether our results can be directly attributed to interactions between hatchery and wild salmon or other factors such as changing local habitats and environments.”
Hatchery fish generally have lower survival rates than wild salmon. There is no silver bullet to this problem, but genomics science is touted as a tool that could boost survival rates of hatchery salmon if applied correctly to hatchery management.
PSF’s review included two reports about genomics technologies and possible applications within SEP hatcheries. The review recommended establishing a robust, integrated science-based program to inform hatchery decision-making.
This would allow further research into epigenetics and Parentage-Based Tagging, two branches of genomics particularly relevant to hatcheries. Both can be used for accurate stock assessment, estimating returns, and for conducting release strategy experiments.
What is genomics?
Genomics is the study of an organism’s genomes – its total genetic material – including how it is affected by its environment. Genomics has been successfully implemented to improve human healthcare, livestock, and aquaculture production and could be used to increase salmon survival from B.C. hatcheries.
Creating a science-based program in B.C., that relies on data from modern technologies like genomics, could make hatcheries more effective by arming hatchery managers across SEP with better information to make decisions.
Positive discussions are already underway with SEP to find ways of implementing all five of PSF’s recommendations into the Program. By working collaboratively with partners and stakeholders, together we can make our hatcheries better at supporting resilient salmon for the future.
Volunteers take DNA samples from hatchery fish
Funding for this project was provided by the BC Salmon Restoration and Innovation Fund, a program funded jointly between Fisheries and Oceans Canada and the Province of British Columbia.
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