Alaska’s state-run hatchery program has long provided a significant portion of the state’s salmon harvest, along with millions in income and jobs for the Alaskan people. There have been, however, concerns regarding the interactions of these hatchery-reared salmon on wild stocks. And while there has been considerable research on this topic, little of it has dealt specifically with Alaska’s habitats or the types of fish reared in Alaskan hatcheries.
For that reason, when the government of Alaska changed over four years ago, the new director of the Department of Fish & Game ordered a study be conducted to develop information specific to the Alaskan hatchery program.
“They thought of three questions that need to be addressed,” says Ron Josephson, Section Chief for the Alaskan Department of Fish & Game’s Fisheries Monitoring, Permitting and Development Section: “First, are hatchery-bred salmon interbreeding with wild salmon to the extent that fitness and productivity of these wild stocks are being diminished? Two, is the annual assessment of wild stocks so biased by the presence of hatchery salmon that excessive harvest of wild fish is being allowed? Third, do density interactions diminish productivity of wild salmon?”
Between the state and the hatchery sector, a science panel was developed – the Alaska Hatchery Research Group.
“It’s a cross section of people that would develop the type of projects that will help answer these questions about interactions between wild and hatched fish in wild environments,” says Josephson.
Several phases of the study are currently underway. Straying studies will sample salmon indicator streams to estimate the hatchery fraction in natural systems on a district scale. Ocean sampling at the entrances to Prince William Sound will provide unbiased estimates of the hatchery fraction in the total return of pink and chum salmon. Combining this information with estimates from streams and known removals will allow an estimate of the number of wild salmon spawning in streams, the number of hatchery salmon spawning in streams and the total return of natural fish. Preliminary results from these phases of the study are starting to come in.
“We’ve got direct evidence that the proportion of hatchery fish coming back to Prince William Sound for pink and chum salmon is about 20% less in the return than it is in the harvest,” says Josephson. “We’re definitely successful in managing those fisheries to harvest a higher rate of hatchery fish than wild fish. We’re right on the cusp of being able to put together an estimate on the total return of pink salmon and chum salmon in Prince William Sound along with the numbers of spawners.”
The project also includes a study of the fitness of the salmon in question – the ability to both survive and reproduce. Genetic analyses can trace an individual fish’s respective parents, so long as the parents were genetically sampled. Using these tools, reproductive success can be estimated for hatchery-origin and natural origin fish in each stream. They can also provide data for comparisons between low and high stray rates for each of the two species, which will be used to estimate survival rates and reproductive success to the adult stage.
“The real valuable data comes from adults,” says Josephson. “Being able to produce offspring that spawn is the important thing. Being able to spawn a fish that will die out at sea isn’t that important.”
Josephson says that department expects the long-term study will conclude between 2020 and 2025.
– Matt Jones