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News from the Department of Biological Sciences

Monitoring threatened species: A fish story

Biology professor David Cowles dons waders each fall to hike up the streams of the Umatilla National Forest looking for bull trout

Bull trout. Photo by Joel Sartore for National Geographic Stock with Wade Fredenberg/USFWS

A WWU student hikes up a stream looking for bull trout redds.

Each fall for the last 10 years, Walla Walla University professor of biology David Cowles has joined the Umatilla Forest Service on their annual survey of bull trout spawning. The Umatilla National Forest is home to many mountain streams where the threatened fish come to breed. WWU students often join Cowles to volunteer on the survey, giving them valuable real-life biology experience while working with professional field biologists.

Employees of the Umatilla Forest Service and State and U.S. Fish and Wildlife Service join forces with volunteers from local Native American tribes and other interested parties like Cowles to make up the surveying group. During the survey, streams are divided into “reaches” of one to two miles. Team members put on waders and hike up the stream searching for characteristic “redds”—the place where the trout lay their eggs.

“Once the bull trout have reached the area of the stream they were born in, they pair off,” says Cowles. “The female finds an area of clean gravel and moderate current and begins digging a hole with her tail. After a hole is dug, she lays her eggs on the gravel while the male swims around and releases milt (sperm) to fertilize them. Then she moves slightly upstream and digs up more gravel to flip over and cover the eggs. After laying the eggs, the bull trout watch over the area for several more days or weeks until they die.”

The redds create a very distinct disturbance in the streambed that is easily spotted by the surveying scientists. Each redd that is discovered is carefully catalogued and marked. The entire process takes about a day to complete.

Threatened species
There are many beautiful mountain streams in the Umatilla National Forest, but only a few are capable of supporting bull trout, which is an especially sensitive species. They are sensitive to silt, which can build up between the gravel and suffocate the eggs. Like other types of trout and salmon, they need clean and cold water to successfully reproduce, which makes them much more vulnerable to changes in environmental factors. Human projects cause silt to increase in streams, and climate change increases water temperature beyond what the fish can handle.

“Since they are so sensitive to environmental conditions, they are an important environmental indicator—like the canary in the coal mine,” says Cowles. “They are one of the first species that starts running into trouble if conditions start to deteriorate. It is now known that these spawning fish are a very important source of nutrients for these forest streams, which are then distributed through the forest as the fish are eaten by various animals and birds.”

The survey project has proved to be a valuable learning tool as interested students have joined the project and worked side by side with professional biologists. One WWU biology graduate student did a study on the streams to determine ideal conditions for the bull trout.

“This project gives us a chance to contribute to our community in ways that are natural and exciting for biologists,” says Cowles. “If students do have interest in pursuing a career in field biology, it also gives them invaluable contacts and knowledge that can help them get started.”

Posted September 23, 2016

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Last update on March 7, 2018