The good news is that the state of the science regarding hatchery-wild salmon interactions has evolved substantially.
The bad news is that that newer science seems to show those hatchery salmon and steelhead don’t do too well when they stray onto the spawning grounds and in many cases negatively affect wild fish they mingle with there.
The past two decades of research on Pacific salmon “tend to show poor reproductive success of hatchery fish when they spawn in the natural environment,” Michal Ford told the Northwest Power and Conservation Council during its mid-September meeting in Bend, Ore.
Those studies also show “large scale negative associations between the presence of hatchery fish, either release or spawners, in the natural environment and wild population performance,” according to Ford, director of the Conservation Biology Program at NOAA Fisheries’ Northwest Fisheries Science Center in Seattle. He was asked to brief the Council on the state of the science on hatchery effectiveness.
Hatcheries have been in existence in the Pacific Northwest for more than 100 years, sending up to a half billion salmon and steelhead toward the Pacific Ocean back during the peak of production in the 1950s and 1960s. The hatcheries had a variety of purposes, such as mitigating for the loss of wild production because of habitat losses, boosting ocean and freshwater fisheries and conserving species.
Hatchery fish benefits include providing target stocks for numerous fisheries that rely on hatchery production. They also can benefit fish conservation through supplementation of depleted stocks and providing DNA to fill gene banks. They also provide ecosystem help by serving as food for such animals as Orca whales and they bring marine nutrients back to terrestrial ecosystems.
Scientists say they also pose biological risks to wild salmon through genetics (domestication, loss of diversity) and in ecosystem interactions (competition, predation, disease).
There are a total of 13 salmon and steelhead stocks in the Columbia River basin alone that are listed under the Endangered Species Act. NOAA Fisheries is charged with, among other things, the wild, naturally produced portions of those runs. In doing so it attempts to balance the need to provide fisheries in freshwater and at sea.
Ford listed some of the implications hatchery interactions could have on wild fish recovery strategies:
-- Current science indicates that limiting natural spawning of hatchery fish is generally beneficial to wild populations, though he emphasized some safety net programs are important to conserve particular flagging salmon stocks.
-- There is evidence that reducing hatchery production leads to increased wild production.
-- Quantifying the cumulative effects of hatchery releases is very important and could be a factor limiting recovery of some ESUs.
The first listings in the early 1990s coincided with an upswing in research activity aimed at understanding relationships between hatchery raised and wild fish. Relative productivity was a topic little researched 10 years ago, Ford said. Now there are at least 20 published research papers analyzing reproductive success.
“Now we have a much clearer idea of how successful hatchery fish are when they spawn naturally” and how that comingling might affect wild fish fitness and productivity, Ford said.
He used as an example, recent research in the central Washington’s Wenatchee River basin where chinook spawners were captured and sampled at Tumwater Dam to determine if they were wild or hatchery fish and then released to complete their mission. When their progeny were sampled, either as juveniles or returning adults, “you can do genetic analysis and you can figure out basically which progeny were the product of which parent,” Ford said. He showed the Council data from 2005.
“In this particular year, this particular study, you can see that the hatchery fish produced about half, a little less than half, of the offspring than did the wild fish,” Ford said.
A review by the NWFSC of all of the available literature showed similar results, higher wild productivity in all but a few instances.
Another study, of steelhead in Oregon’s Hood River basin, showed that hatchery produced fish with at least one wild parent did much better when spawning in the wild than did fish with 100 percent hatchery raised parents.
“There’s a little bit of a tendency for the more ancient and more non-local broodstock to do worse,” Ford said of fish with a long history of captivity and/or from other river basins that try to spawn in the wild.
In summary, Ford said that hatchery fishes’ reproductive success is generally lower than wild fish and:
-- That’s true for both “supplementation” and “production” programs.
-- Hatchery steelhead may have particularly low reproductive success
-- There’s lots of variation.
Those conclusions are based on studies of spring chinook, steelhead, coho and Atlantic salmon There’s limited information on sub-yearling release strategies -- fall chinook, chum, pink.
Why is there such a differential in reproductive success and overall fitness? Answers are emerging there as well, Ford said. His “summary of causes” includes:
-- Evidence of both environmental and heritable effects.
-- Genetic architecture of differences unknown.
-- No general trend at this point in the relative importance of genetic versus environmental effects.
Ford’s Powerpoint presentation can be found at:
Ford offered the following links for “further reading:”
RIST hatchery report:
State of the Salmon Ecological Interactions Conference: