The mysteries of migration

Brett Bowersox of the Idaho Department of Fish and Game and University of Idaho graduate student Stacy Feeken prepare to track radio-tagged steelhead in the lower Clearwater River. Eric Barker / Lewiston Tribune

University of Idaho graduate student Stacy Feeken holds a radio telemetry tag. The tags are placed in the mouths of steelhead at Lower Granite Dam, allowing the fish to be tracked as they move upriver. Eric Barker / Lewiston Tribune

GIBBS EDDY — On a recent morning, University of Idaho graduate student Stacy Feeken and Idaho Fish and Game biologist Brett Bowersox launched a drift boat, equipped with a large antenna, into the lower Clearwater River.

The river was flowing high, and temperatures were cool as Feeken rowed and listened intently for faint squawks from a receiver — an indication a tagged steelhead was holding nearby.

Feeken and Idaho Fish and Game biologists are in the second year of a two-year study looking at how different groups of adult steelhead use the Clearwater River. The fish are implanted with radio telemetry tags that allow them to be tracked as they swim upstream. The tags, about the size of one AA battery with a long wire attached, are inserted down the gullets of the fish at Lower Granite Dam.

After that, Feeken and an assistant drive up and down the Clearwater River, or float various stretches of the river, throughout the season, to track the fish. Their work starts in September and continues into June.

Thus far, their research is showing both hatchery and wild adult steelhead in the Clearwater River have strong fidelity to their places of origin. That means hatchery fish are returning to either the hatcheries where they were raised or to off-site spots where they were acclimated as juveniles before release. For wild fish, it means a return to their natal (birth) streams, such as Fish Creek, a tributary to the Lochsa River.

The study is also hinting that a new broodstock the department is developing in the South Fork of the Clearwater will produce better returns of hatchery fish there. Over the past few years, the department has made a concerted effort to partner with anglers to catch steelhead in the South Fork and use those fish for separate spawning. The idea is to create a local stock of fish that have shown the proclivity to return to the South Fork.

In past years, steelhead juveniles released in the South Fork came from a larger group that was raised at Dworshak National Fish Hatchery and released at various locations. Bowersox said offspring of adult hatchery steelhead captured from the South Fork and segregated during spawning are showing a 15 percent to 20 percent higher return rate compared to steelhead from the unsegregated group raised at the hatchery.

“That is a good first indication that there is a response with the local broodstock, and they are returning at a higher rate,” he said.

The study, to date, is also showing different groups of fish are not straying into areas they don’t belong. Fisheries managers have long worried that hatchery fish in particular stray at an abnormally high rate and may be harming wild fish by spawning with them.

“The wild fish are returning to their natal streams, and the hatchery fish are concentrating around the hatchery release locations,” Bowersox said. “We haven’t seen any head off in a weird direction.”

The goal of the study is to learn more about the ways various groups of steelhead use the Clearwater River.

“We have understanding of when those fish come over Lower Granite (Dam) based on detections in the ladder for hatchery stock, and we have some information from the fishery of where they are harvested,” Bowersox said.

“We don’t have a finer-scale picture of how those fish are moving through the mainstem Clearwater. So it helps us understand the differences in movements between the hatchery fish and wild fish, and it also helps us evaluate the release strategies of the hatchery fish to determine how high a rate are they returning to their release areas. And the same for the wild fish as well — not the release areas but their natal tributaries,” he said.

Another component of the study simultaneously tracks angler distribution so the information can be compared side by side.

“That gives us the ability to understand how the fish are moving and also couple that with how the fishery is moving and where anglers are focusing and understanding the movement of the fish and the fishery,” Bowersox said.

Wild steelhead from the Potlatch River basin are some of the first to return in the fall and the first to nose into their natal streams in the winter and spring.

“They arrive the earliest of all my fish,” Feeken said.

Conversely, wild steelhead from Fish Creek take their time. About half of that group overwinters in the Snake River, and some don’t enter the Lochsa and Fish Creek until late in the spring. The other half overwinters in the lower Clearwater River.

“The Lochsa fish are the last fish to move all the way up through the system,” Feeken said.

Throughout their recent hour-plus float, the receiver squawked just one time — for a long-since diseased fall chinook that was part of another study. Just the day before, another member of the study group detected several steelhead holding in the same stretch of the lower Clearwater. Bowersox speculated the high flows may have prompted those fish to move upstream.

“Maybe they are moving and shaking; it’s getting close to that time of year,” he said.

He was right. Later in the week, a fixed antenna near the mouth of the Potlatch River showed one steelhead had moved up the tributary. Another survey conducted by driving along the Clearwater detected one fish had moved just upstream of Gibbs Eddy.

Feeken said both the calendar and the increases in flow often cause fish movement this time of year.

The hatchery fish spend time in the lower Clearwater River in the fall, then move upstream as the weather cools and hang out near Dworshak National Fish Hatchery or higher.

“I have Dworshak fish, and there are some fish that are released near the hatchery and some that are released in the South Fork. And those fish I see in the lower Clearwater River early on in the fall, but they move quickly up toward the North Fork and South Fork and hang out in the upper reaches of the Clearwater throughout the rest of the year,” Feeken said.

Bowersox said anglers tend to move upstream following big slugs of hatchery fish, and the wild fish don’t tend to commingle with them near the hatchery. Even though anglers catch wild fish in the lower Clearwater during the fall, angler pressure on them is alleviated as the hatchery fish and fishermen move upstream.

“I think it’s giving us some good information that is showing us our hatchery releases are returning to those areas, and our anglers are keyed into those types of areas and (angler) distribution is focused in on the hatchery part of the run,” he said. “We know the fishery overlaps some with the wild stock, and that is how it’s managed. But we can say we are also seeing, with the diversity and the different migration characteristics the wild groups have, they are not occupying those areas where there is a lot of effort focused on hatchery fish.”