Big One May Get Away - For Good Chinook Salmon Downsized In Response To Fishing Pressure

If it seems as though it’s getting tougher to catch a big chinook, you’re right. And now you have the proof.

The Washington Department of Fish and Wildlife addresses the problem in the draft environmental impact statement on its wild salmonid plan.

Each salmonid species made a lot of tradeoffs during its evolutionary history, the draft says, and chinook salmon went with large size as a way to beat the competition. But, over the last several years, that benefit has been shrinking.

“Populations are younger, smaller and have a higher percentage of males than existed historically,” the report says. ‘Small 3-year-old females were a minor component (of runs) in the early 1900s when spawning and incubation flows were much more stable.”

But now they’re not, because so many of the older and larger fish are caught before they reach the spawning areas. And the now-relatively-abundant 3-year-olds, in addition to producing fewer eggs per fish, are barely capable of burying the eggs deep enough to survive the scouring effect of high stream flows. Chinook are mainstem spawners, and their eggs can be particularly vulnerable to heavy flows.

Coho spawn primarily as 3-year-olds. But they, too, are returning smaller and with fewer eggs, the draft says.

Hook-and-line gear and large-mesh gillnets continually select the larger individuals from coho and chinook populations. Besides that, chinook fish that tend to live longer and grow larger are at added risk of being caught before spawning, because they’re exposed longer to being caught.

Over time, this selection results in smaller fish - those genetically incapable of growing large - doing most of the reproducing, passing their genetic heritage to future generations.

Sam Wright, a fisheries biologist who has come out of retirement to help the Department of Fish and Wildlife develop and implement its wild salmonid plan, says people will have to change the way they harvest so that the catch is representative of the population.

And the ways to do it are there.

“We’re going to have to get away from using size limits in some cases,” Wright said. In other words, anglers would have to keep the first two salmon they caught on a given day, regardless of whether they were foot-long shakers or record-book hogs.

“And we can control gillnet mesh size toward the same end,” he said. “‘We could even use random-mesh gillnets. Variable-size mesh.”