A record run of wild spring run Chinook salmon on a Sacramento River tributary turned into a disaster when the majority of fish perished before spawning last year.
In May, the CDFW published a monitoring report on 2021's spring Chinook salmon run on Butte Creek, a Sacramento River tributary, revealing that 91 percent of the adult fish died before spawning.
An estimated 19,773 out of the over 21,580 fish total that returned to spawn in the Butte County stream perished before spawning. Only an estimated 1,807 adults survived to spawn in a year with a record return of fish.
The number of adult spring-run Chinook salmon (SRCS) that died before spawning is worse than the preliminary estimate by the CDFW in October 2021 that 14,500 out of 18,000 to 20,000 fish had perished before spawning.
The CDFW reported that the “total SRCS population that did not survive to spawn in 2021 was estimated at 19,773. The carcass survey was conducted over 5 weeks from September 21 to October 21. A modified CJS model estimated the 2021 SRCS spawning population to be 1,807.”
The fish perished from disease in the crowded, warm water conditions on the creek that developed before PG&E released colder water into the creek, under pressure from conservationists and anglers.
“The 2021 adult SRCS returning cohort was estimated at over 21,580, and based on field observations and survey estimates, the density of the population in the upper reaches of the holding habitat likely exacerbated the spread of pathogen transmission and contributed to the rapid spike in pre-spawn mortality,” the report concluded.
The full report is available at: www.buttecreek.org
Fish advocates have criticized the CDFW and other government agencies for failing to exert needed pressure on PG&E, the current owner of the hydroelectric project on Butte Creek, to release colder flows when they were needed to alleviate the massive fish kill.
PG&E’s De Sabla/Centerville project brings West Branch Feather River water over the mountain from Phillbook Reservoir and Round Valley Reservoir to Butte Creek to be used for hydroelectric power.
This year’s spring Chinook run got off to a rough start when over 200 adult spring Chinook perished in a slough connected to Butte Creek in the Butte Sink in March after flows were increased in the slough for irrigation purposes and then were slashed, resulting in the fish being left high and dry.
“We have run out of options and we are running out of time,” said Allen Harthorn, Executive Director of Friends of Butte Creek. “Butte Creek salmon will only survive if we get them up to colder water. It’s that simple.”
Butte Creek has the largest self-sustaining, naturally spawning, wild population of spring Chinook salmon in the Central Valley.
In addition, 97.4 percent of winter-run Chinook salmon juveniles in the Sacramento River perished as water was delivered to water contractors while the Bureau of Reclamation violated their own plan to only kill 80 percent of winter run salmon every day but one through the diversion season.
The winter Chinook is one of four runs of salmon on the Sacramento River, including the spring, fall, late fall and winter runs. The spring and winter runs are listed under the federal Endangered Species Act (ESA) and the California Endangered Species Act (CESA).