Tiny chips and fish ‘Social Security numbers’ help IDFG track salmon, steelhead survival

·5 min read

Devan Reid grabbed a lethargic juvenile steelhead out of a plastic bin, deftly flipped it upside down and quickly inserted a tiny glass-encased computer chip into its abdominal cavity.

A detector displayed the unique number of the Passive Integrated Transponder tag, also known as a PIT tag, that will stay in the belly of the fish throughout its life.

“That number, that is his Social Security number,” said Scott Putnam, a biologist with the Idaho Department of Fish and Game. “That way we will be able to track him from here to, well, forever.”

Reid, a senior fisheries technician for the agency, passed the smolt to his colleague, David Overy, who measured it, recorded its condition and placed it in another bin to recover from the short procedure that included a dose of anesthetic.

The fisheries workers continued the pattern until they’d worked through 10 fish — nine steelhead and one spring chinook — the trap’s catch for the past 24 hours. Above them, cars and trucks hurried across the Interstate Bridge, and beneath their feet the Snake River continued its languid pace toward the Pacific Ocean.

Their work at the trap April 21 was short. But the pace should soon pick up as the river’s flow rises and hundreds and sometimes thousands of juvenile fish are diverted into the floating contraption each day. Together with data collected from a second Idaho trap on the lower Salmon River near White Bird, traps on the Grande Ronde and Imnaha rivers in Oregon and Washington, plus monitoring that happens at dams on the Snake and Columbia rivers, the recorded information helps fisheries managers and scientists keep tabs on the annual migration of salmon and steelhead during their migration to the Pacific Ocean.

It’s all part of the Smolt Monitoring Program managed by the Fish Passage Center at Portland.

“The purpose is to develop and maintain a time series of data and fish travel time and migration characteristics to help manage conditions to get the highest survival we can with the tools we have for downstream migration of salmon and steelhead,” said Michele DeHart, director of the Fish Passage Center. “The monitoring is how the fish tell us what is working and what is not.”

Most of the fish that show up come from hatcheries. But the aim of the program is to glean information that will improve survival for fish listed as threatened and endangered under the federal Endangered Species Act. So they are especially interested in fish that began their lives in the streams of Idaho’s mountains.

“The money fish for us is the wild fish,” Putnam said. “We use the hatchery fish as a surrogate for the wild fish, but ultimately the wild fish (is what we are after).”

The program began in 1983. For more than 20 years, Putnam has worked on and then overseen the traps in Idaho, including a trap on the lower Clearwater River that is no longer in use. Because the program spans decades, Putnam said he has to take care to ensure he doesn’t make changes that will skew data. Sometimes that means sacrificing efficiency for consistency.

“A little change, such as the type of needle we use or the trapping hours, or methods, really impact the big picture because we are building a long-term data set,” he said. “So what we change today could throw us off when looking at numbers from the 1980s.”

They still take advantage of technology. On Thursday, Reid and Overy used a digital board, somewhat like the touchpads workers use to place orders at fast-food restaurants, to speed their work.

“We will handle up to 4,000 fish a day once things get rolling,” Putnam said. “We can mass run them through here, and that digitizing allows us to do that.”

The Snake River trap operates 24 hours a day. Years ago, Putnam or others would have to check on the trap every few hours to make sure it didn’t become clogged with debris. That meant jumping on a boat and motoring out to the trap. Now that monitoring happens via a security camera that beams its video over the internet.

“It used to be that we had to come out here and check this thing every two hours. Now I can literally do it from a smartphone,” Putnam said.

When flows rise quickly, debris that includes large logs can sometimes amass on the trap.

“Most of the folks in town when they come across the bridge, they have no idea what this thing is,” Reid said. “They sometimes do think we are out here trying to sample woody debris.”

Putnam will pull the trap if conditions become too dangerous. But he notes that juvenile wild steelhead tend to move in large numbers when the river is high.

“As log numbers go up, so do fish numbers,” he said.

“There is a lot of focus on wild steelhead as far as how they make it through the migration corridor so we want to get as many PIT tags in wild steelhead as we can. In order to do that, we have to be running these traps in the worst of times, when debris is moving, turbidity is terrible. When you see all the logs building up in my fish trap, it’s because I’m trying to get wild steelhead.”

After the fish were processed, they were placed in a net pen that floats alongside the trap. It has a large mesh size on the upstream end that allows the fish to leave voluntarily but isn’t so big that predators can get in.

“We want to make sure these fish really have a chance to revive before a northern pikeminnow will take them out,” Putnam said.

When they are ready, the fish exit and resume their trip to the ocean.

Putnam produces weekly blog posts on the smolt monitoring program. The latest is available at bit.ly/3enIrGd and previous posts can be found at idfg.idaho.gov/fish/wild.