Field biologists are reporting the largest number of endangered coho salmon returning to spawn in tributaries of the Russian River in more than a decade.
Most of these fish were released as fingerlings into the river system, as part of a captive broodstock program at Don Clausen Warm Springs Hatchery on Lake Sonoma that began 10 years ago, when wild coho salmon were rapidly vanishing from the region.
"We were very excited to observe so many adult coho return and spawn this winter," said Mariska Obedzinski, lead biologist and monitoring program manager with California Sea Grant. "A lot of people are working hard to improve conditions for coho in the Russian, and this is a hopeful sign that our efforts are starting to pay off."
Since the launch of the recovery program in 2001, returning adult coho salmon averaged less than four per year. These low numbers were the catalyst for the Russian River Coho Salmon Captive Broodstock Program, a recovery effort in which offspring from hatchery-reared adults are released into the river system.
This year, biologists estimate that more than 190 adult coho have returned to the Russian River watershed, beginning with early storms in October and peaking in December. Promisingly, a few coho are being sighted in unstocked creeks, utilizing habitat beyond those tributaries in which coho are released.
"We are hopeful this trend will continue and the Russian River coho salmon population will establish self-sustaining runs," said Paul Olin, an advisor with California Sea Grant Extension, who oversees monitoring of juvenile and adult salmon in the river system. "This program might help guide recovery efforts for many other remnant populations of coho salmon in California."
Coho salmon abundance has declined dramatically statewide in the past few decades. Biologists believe that additional captive breeding efforts and other focused recovery measures will likely have to be instituted to prevent widespread extinction of coho salmon in Central California.