Threatened spring-run chinook salmon are sparse this year
PUBLISHED: September 24, 2018 at 3:27 pm | UPDATED: September 25, 2018 at 10:40 am
The rare spring-run chinook salmon is rarer than usual this year, according to counts in the three streams that support the bulk of the wild fish left in the Sacramento River system.
In Butte Creek, a snorkel survey counted 2,118 fish this year, according to Colin Purdy, who supervises the count for the state Department of Fish and Wildlife. That’s less than half the average since 1989 of 4,427 fish.
“It is low unfortunately,” he said, “but it’s better than last year.”
In 2017, only 950 fish were counted.
The record was in 2001, when the carcass survey turned up 18,312 fish.
The carcass survey is the second count Fish and Wildlife does of the salmon in Butte Creek, and is made possible by the lifecycle of the fish.
The spring-run fish return from the ocean in spring, almost always to the streams where they were born. They head far upstream into the foothills and spend the summer in deep, cool pools of water, before spawning in the fall. After they spawn, they die. Their offspring will later head downstream and out to the ocean, spending two or three years there before returning to complete the cycle.
As a result of the lifecycle, the creeks are full of dead fish after the spawning cycle ends. The nutrients of their bodies sustain a number of birds, animals and other fish, and enrich the food value of the water in the creeks.
The dead fish are also easy to count. Fish and Wildlife technicians will walk the creek after the spawn and count the carcasses, marking each one so it isn’t counted twice.
Purdy said in years when there are a lot of fish, the carcass count is far more accurate than the snorkel count. But in a low year like this one, the snorkel count is probably pretty accurate.
He said as of Friday, spawning hadn’t started in the creek, but he expected this week to see the female fish building the redds where they will lay their eggs. Male fish will then spray their sperm on the egg masses, and the new generation will begin.
The spring-run used to be the largest of the chinook runs in the Central Valley. But construction of dams like Shasta and Oroville blocked access to the higher-elevation cool water the fish need to survive the summer, and the numbers dropped. The spring-run is now listed as threatened on both the state and federal endangered species lists.
Deer and Mill creeks
Two eastern Tehama County creeks support most of the spring-run salmon that don’t head up Butte Creek, and this year, their numbers are terribly low.
In Mill Creek, just 51 salmon were counted, according to Fish and Wildlife environmental scientist Matt Johnson. That’s the worst ever, in a count that goes back to 1970. In Deer Creek, there were 159 fish, about the third lowest on record.
“I think we are seeing the continued effects of the severe drought we were in,” Johnson said.
He explained that when the fish returning this year were born, they had really poor conditions in the fresh water, with low levels of warm water. Then when they got to the ocean, the water there was warmer than usual, which isn’t good for the fish. “It was basically a double whammy.”
If there is good news in Tehama County, it’s that the new fish ladder around Lower Deer Creek Falls appears to be a success.
The falls, about 35 miles upstream from the Sacramento River, are a 15-foot barrier to fish moving upstream. A fish ladder was built around the falls in the 1940s, but it was steep and didn’t work well. Johnson said most of the spring-run in Deer Creek spawned in areas below the falls.
However in 2016 and 2017, a new, longer ladder with more, shallower steps was completed, and this year the snorkel survey found about 73 percent of the spring-run in the creek were upstream from the falls.
The counts are done differently on Deer and Mill creeks. The official count is done by video taken at a station the fish swim past on their way upstream.
Johnson said he was hoping for a recovery in the number of fish next year. “The conditions for next year’s returning fish look better,” he said.