Two fish traps using large rotating drums to funnel fish into holding tanks have been lowered into the Russian River near Forestville for the annual chinook salmon survey that began Wednesday.
The decadelong survey is the only count of chinook smolt in a California coastal stream, and it has uncovered a healthy population in the Russian River that no one believed existed, said Sonoma County Water Agency biologists.
?We really wouldn?t have known about the chinook presence in the Russian River. The original intent was to collect information on steelhead and coho,? said Dave Manning, a biologist and senior environmental specialist for the Water Agency.
Chinook, as well as coho salmon, are on the federal endangered list.
?We found that there is this self-sustaining population of chinook, they are the largest component of the fishery in the Russian River ? and that came as a surprise to many people,? Manning said.
The fish traps are mounted on pontoons and were lifted into the Russian River just downstream of Wohler Bridge on Tuesday.
The drums turn slowly in the river?s current, churning the dark green water and drawing the small fish into holding tanks.
Each day, biologists will empty the tanks to measure and identify the fish. Some will have a fin clipped and then be released upstream to see if they are caught again.
The fish that are scooped up are usually two to three inches and migrating to the ocean, providing an indication of the number of adults that had traveled up the river months earlier to spawn.
Biologists, who said the migration season is just getting started, found a half dozen chinook, two small coho and a few hatchery-raised steelhead in the traps on Wednesday.