Dipping a small net into the clear water of Porter Creek, biologist Ben White delivered a few dozen squirming, silver coho salmon fingerlings into their new home Monday.
Morning fog lingered over the creek, a tributary of the nearby Russian River, as White and his three-man team from the Warm Springs Dam fish hatchery donned waterproof waders to deliver about 6,000 of the hatchery’s latest offspring into their adopted home.
Several of the 4-inch-long salmon immediately took shelter beneath the overhang of an underwater rock, a good choice, White said. Scientists expect the fish, about 10 months old, to quickly form a biological imprint with the creek and return, should they survive, in two or three years to spawn as adults.
“The hope is they will hunker down for the winter in Porter Creek and migrate out (to the ocean) in spring,” said White, who is lead biologist for the hatchery-based coho salmon recovery program.
Prized by anglers, the coho are closely monitored, as if they were precious cargo, for they represent the future of a diminished and officially endangered species.
A tiny, magnetized stainless steel wire tag is embedded in the snout of every hatchery-bred salmon to let researchers know they are hatchery-bred as opposed to wild fish. Anglers are not allowed to keep any coho caught in the river system.
Fifteen percent of the coho also receive a passive integrated transponder, or PIT tag, the size of a grain of rice and similar to the hardware in the FasTrak toll collection system on San Francisco Bay bridges, White said. More than 80 antenna arrays in the river and larger tributaries detect and record the fish-identifying data stored on each tag.
Coho fingerlings sometimes move out of the streams in which they were released, and tag surveys enable biologists to determine their migrating routes and survival rates, White said.
Porter Creek, running for nearly two miles through the 1,500-acre E&J Gallo-owned MacMurray Ranch on Westside Road, was pumped up after last weekend’s heavy rains.
“It’s been a while since we had good flows this time of year,” White said, adding that the extra water should enhance survival of the freshly released salmon.
When finished, the fall release will put 100,000 coho in 10 Russian River tributaries, he said.
Coho were once so abundant in the Russian River system they supported a commercial harvest of more than 13,000 fish a year. But decades of development, including construction of dams at Lake Sonoma and Lake Mendocino, reduced the population to about 100 adult fish in 1999.
Federal fisheries officials have established a recovery target of 10,100 adult coho returning each winter to the Russian River system, and there is a long way to go.
Last winter, PIT tag data were used to estimate a return of 192 adult fish, about half as many as the winter of 2014-15 and even farther below the estimate of nearly 550 in 2012-13, the peak number since 2000-01.
Gallo, along with neighboring Sweetwater Spring Ranch and the Sonoma Resource Conservation District, are partners in the Porter Creek salmon restoration effort, said John Nagle, Gallo’s environmental manager.
In four recent drought years, Gallo released water from a MacMurray Ranch reservoir to augment the creek’s water flow, he said. The sprawling ranch, in a bucolic rural valley ringed by forested hills, includes 427 acres of vineyards and was purchased by Gallo from actor Fred MacMurray’s family in 1996.