One fish, two fish
Results of Big Creek survey released
The results of a fish survey conducted last August in Chico State’s Big Chico Creek Ecological Reserve have been made public and are kind of a mixed bag. But as fisheries biologists Michael Hellmair and Dana Lee point out, this was the first survey of the creek in more than 10 years, and as such, it serves as a baseline for future counts, the next of which is scheduled for August.
Hellmair and Lee work for research firm FISHBIO, which is based in Oakdale and opened an office in downtown Chico two years ago. The survey was done without monetary compensation.
Last August, FISHBIO founder Doug Demko described the survey as a way to give back to the community and as part of an ongoing project to monitor the health of the creek by noting fluctuations in the fish populations.
The report says that five species of fish were observed during the survey—rainbow trout, brown trout, Sacramento sucker, riffle sculpin and California roach. Rainbow trout were the most abundant with an estimated 2,525 within the reserve. Brown trout count estimations put the population at 188 and only one adult steelhead was spotted. Estimates were not made for the other three species, the report says, though 36 suckers and sculpin were observed.
Demko had previously explained that rainbow trout and steelhead are basically the same species of fish. The difference is in their respective lifestyles. Rainbow trout never leave freshwater habitats, while steelhead, which tend to be larger (18 inches in length or longer), live in the ocean, but return to their native freshwater creeks to spawn. Rainbow trout and steelhead are considered native to the creek. Brown trout were introduced a number of years ago.
Hellmair said while it’s too early in the survey process to make definitive conclusions, he said for the size of the creek the number of trout counted is a good sign.
“Because the rainbow and steelhead populations are so intermeshed,” he said, “the resident rainbow trout population sort of provides a gene bank during years when juveniles that decide to be steelhead can’t make it to the ocean or the adult steelhead can’t make it back.”
He said it’s not feasible to count every fish in such a survey and that the numbers are based on sample habitat areas where the surveyors snorkeled and counted the fish.
“We make projections and extrapolate that to the rest of the reserve,” he said. “For the size of Big Chico Creek, given that in most places you can probably wade across it without getting your knees wet, it’s definitely a sizable and seemingly healthy trout population, especially within the boundaries of the ecological reserve. In part, it’s probably because further environmental degradation in Big Chico Creek has come to a halt mostly due to the protection that is afforded by the designation as an ecological preserve.”
In the past, that degradation was caused by upstream logging, mining impacts and agricultural runoff, he said.
It is too early to tell if and how the ongoing drought has impacted the fish, he said.
“There’s been less runoff this year than last year and who knows what’s to come in future years? But it will certainly make for tougher conditions,” Hellmair said.
Fellow fisheries biologist Lee said discovering the similarities between steelhead and rainbow trout is both interesting and confusing.
“I would think of them as two different populations with no inter-breeding,” he said. “They’re just kind of finding out they could depend on whatever benefits the habitat offers. Each fish is going to do what it can to survive. That means either migrating to the ocean and coming back or staying in the river where there is plenty of food when the stream is in good condition. Then there is no reason to make that trip.”