Sonoma County Hatchery Coho Salmon Relocated to Avoid Heat Stress

Warm Springs Fish Hatchery
Coho salmon from the Warm Springs Fish Hatchery in Geyserville are in temporary residence at a conservation facility at Casa Grande High School in Petaluma, Calif. Photo courtesy of the California Department of Fish and Wildlife.

Some 4,000 California hatchery juvenile coho salmon were relocated from the Warm Springs Fish Hatchery at Geyserville in July and August to a conservation facility at a high school in Petaluma for rearing until conditions improve.

A spokesperson for the California Department of Fish and Wildlife said on Aug. 23 that they are hopeful that drought and poor water conditions at Lake Sonoma will improve enough to allow them to truck the fish back to the hatchery before year’s end.

Beginning in late spring, rising water temperatures at Warm Springs Hatchery increased the risk of heat stress and pathogen outbreaks. Scientists developed the relocation plan as a precaution to keep the hatchery coho safe.

CDFW acting regional manager Stacy Sherman said the agency has a vested interest in seeing coho salmon remain healthy.

“In addition to being endangered, coho are an indicator species and a sign of the health of the watershed,” she explained. “When they’re in danger, action needs to be taken.”

The relocation was made possible through a public-private partnership led by the U.S. Army Corps of Engineers (USACE), which operates the Warm Springs Fish Hatchery. CDFW contributed pathogen testing and logistical support. The student-operated conservation facility, located at Casa Grande High School in Petaluma, is maintained by United Anglers of Casa Grande, Inc. The National Marine Fisheries Service, Monterey Bay Salmon and Trout Project, Sonoma Water and Jackson Family Wines provided funding for the effort.

Coho kept as hatchery broodstock are carefully managed so that their genetic diversity is comparable with wild populations of the Central California Coast Evolutionarily Significant Unit.

CDFW biologists said that with wild populations facing poor river conditions due to drought, captive fish act as insurance against loss of genetic diversity.

“Relocating a portion of the juvenile coho provides additional protection for the maintenance of genetic diversity, which is important for resilience of the species as a whole,” Sherman explained.