Study: Offspring of hatchery fish carry reproductive ‘handicap’

Washougal Salmon Hatchery employee Matt Fischer carries a tray containing 10,000 late-run coho salmon fry to be released into holding ponds earlier this year. A new study raises concern about the reproductive fitness of the offspring of fish raised in hatcheries. (Steven Lane/The Columbian)

A steelhead powers up the East Fork of the Lewis River. A study finds offspring of hatchery-raised steelhead didn’t reproduce as well as wild steelhead offspring. (Files/The Columbian)

Washougal Salmon Hatchery employee Matt Fischer carries a tray containing 10,000 late-run coho salmon fry to be released into holding ponds earlier this year. A new study raises concern about the reproductive fitness of the offspring of fish raised in hatcheries. (Steven Lane/The Columbian)

If you’re a fish raised in captivity, scientists know that it’s hard for you to successfully reproduce in the wild.

Now, it turns out, your kids may have the same curse.

That’s the startling conclusion of a new study by Oregon State University researchers who examined the reproductive success of hatchery-raised and wild steelhead in Oregon’s Hood River.

“I was surprised, frankly,” said researcher Michael Blouin, an OSU zoology professor. “I thought the offspring of hatchery fish would be … pretty much like a wild fish. But, in fact, they’re still carrying a handicap they got from their parents.”

The new research undermines ongoing experiments by state and tribal fishery managers to crossbreed wild fish with fish raised in hatcheries. After more than a century of overfishing and habitat degradation, [URL]hatcheries now produce the overwhelming majority of the salmon and steelhead that return to the Columbia River basin each year. Fishery managers have suggested boosting the last vestiges of wild-spawning native salmon runs by crossbreeding them with relatively abundant hatchery fish.

Doing so may cause more harm than good, according to the OSU researchers.

From a wider lens, the researchers noted that their results could affect thousands of animal species expected to require captive breeding to prevent extinction over the next 200 years.

“Captive-bred organisms could potentially drag down the fitness of the wild populations they are meant to support, even while temporarily boosting their numbers,” the study concluded.

Raised in steel and concrete raceways, hatchery fish aren’t subjected to the same forces of natural selection that cull their wild-spawning cousins. Wild fish first must survive fast-moving currents that eradicate many eggs in the gravelly river bottoms. If they’re lucky enough to emerge from the gravel intact, [/URL]wild fish must find their own food while eluding predators before making their way to the ocean;http://columbian.com/article/20081120/NEWS02/711209932[URL].

The offspring of both hatchery and wild fish face these same obstacles.

Yet, the OSU study found the offspring of two captive-bred parents reproduce at a rate that’s only 37 percent of the offspring of two wild parents. For the offspring of one wild and one hatchery-raised parent, the reproductive fitness is 87 percent of fish with purely wild parentage.

In other words, the behavioral characteristics necessary for survival appear to be embedded within the creature’s genetic makeup.

“This genetic suggestion is pretty startling,” said Brian Gorman, a spokesman for the National Marine Fisheries Service in Seattle.

Researchers haven’t determined what harmful genetic trait the hatchery-raised fish are picking up and passing on to their offspring — or how to rectify it. Blouin suggested one possibility: Hatchery managers may be selecting and crossbreeding fish with a relatively fast growth rate. This may be good for fishermen, but it may be problematic for any offspring produced by the steelhead.

“A fish with a high metabolic rate is going to have to feed a lot more,” Blouin said.

Over time, maladapted genetic traits picked up in the hatchery could be eased out with each succeeding generation of fish spawned in the wild.

However, hatcheries are likely to have an enduring influence. As long as hatcheries continue to exist — producing meat for commercial, sport and tribal fishermen — hatchery-raised fish are likely to continue to stray into wild spawning grounds.

“If you’re adding hatchery fish every year, you’re constantly resetting the clock,” Blouin said.

That’s why it’s so important for hatchery managers to do everything they can to keep hatchery fish away from wild spawners, another scientist said.

Lars Mobrand, a fisheries scientist who served on a federal review of 178 hatcheries operating in the Columbia basin, said hatchery fish should only be deliberately crossbred with wild fish in the most extreme cases. Unless a particular run is about to blink out completely, he said, hatchery fish should never be used to supplement wild runs.

Mobrand said the OSU research, published in the scientific journal Biology Letters, underscores the point.

“We have to go to greater lengths to (enhance) our ability to remove and harvest hatchery fish,” he said. “Those that aren’t harvested ought to be captured.”

Erik Robinson: 360-735-4551, or erik.robinson@columbian.com.[/URL]