Jared Barker, lead technician for Quantitative Consultants, collects fish from a rotary screw trap (© 2018 Cindi Christie/Cyanpixel)
The sight of a bull trout captured in a rotary screw fish trap was cause for excitement as Jared Barker emptied the trap box. It was the largest he said he had seen. Bull trout, chinook salmon, steelhead and cutthroat trout are the “target” fish in a study of juvenile fish migrating from the Lemhi River.
Moments later, Barker and partner Mike Hall, both lead technicians for Quantitative Consultants, checked to see if the fish had been previously tagged. If so, it had been caught before and would be in a database of individual fish. Or, it had swallowed a fish that had been tagged.
“It’s like catching fish in a barrel,” Hall joked.
Biologists and technicians identify, tag, weigh and measure the target fish and then release them upstream to be captured again in the large rotary trap, or downstream if already tagged. That helps estimate the number of out-migrating fish. Biologists and technicians identify, tag, weigh and measure the target fish and then release them upstream to be captured again in the large rotary trap, or downstream if already tagged. That helps estimate the number of out-migrating fish.
Native fish that live in the river year-round also are counted, measured and weighed before being set free downstream. Even sculpin, the bottom of the food chain, are important. Once let go, the bull trout stayed near the trap — perhaps in hopes of an easy meal or two.
Quantitative Consultants is under contract from the Bonneville Power Administration to monitor the population of migrating Chinook salmon and steelhead trout to “offset” the number of these fish that die in BPA’s hydropower systems. The project also is in cooperation with the Idaho Department of Fish and Game.
While most are passing through, those that are repeat visitors can become familiar faces (or fins) and have been given nicknames. Each tagged fish with Passive Integrated Transponder tag that passes over an antenna throughout the watershed is monitored. fish logged can be tracked at Columbia Basin PIT Tag Information System (PTAGIS), a public database.
They study the “relationship between stream habitat and anadromous salmonid populations in the Columbia River basin,” according to their 2017 annual report to landowners along the Lemhi River and tributaries who have granted access through their private property.