Researchers have used genetic testing to uncover a distressing fact about fall-run Chinook salmon in the Mokelume River; only 10% of the fish are truly “wild.”
Only about 10 percent of the fall-run Chinook that spawn in the river are naturally born fish, according to a genetic study released this past week. The dismal count of wild fish, which experts believe would be just as bad in other California rivers, means there are not enough native chinook to sustain a natural population in the river.
“We expected to find hatchery fish, but the sheer number of hatchery fish returning to spawn in the wild is surprising,” said Rachel Johnson, a fishery biologist for UC Santa Cruz and the U.S. Bureau of Reclamation and a co-author of the study. “It looked like a healthy population of fish returning to spawn, but the reality is that without the hatchery fish the wild stocks are not sustaining themselves.”
Recent studies suggest hatchery fish degrade the survivability of wild stocks within one generation, so even as hatchery fish are used to make up the numbers of the wild runs, they actually make the wild fish less competitive.
It’s yet more evidence that wild salmon stocks must be protected and restored wherever possible (including the Klamath River).
Read the entire SF Chronicle article here.