A fish’s life can cover many miles

Fisheries researchers from the Idaho Department of Fish and Game and Idaho Power Co. have documented the long-distance movements of a particular bull trout.

The nearly 200-mile annual trek through varied habitat is remarkable to contemplate but likely not unique for bull trout that are listed as threatened under the Endangered Species Act.

Jordan Messner, fisheries manager for the Idaho Department of Fish and Game’s McCall-based southwest region recently detailed the journey of the fish in a blog post.

The fish was captured by Idaho Power biologists in Hells Canyon in 2018 and inserted with a passive integrated transponder tag. It was just 1 foot long at that time.

The fish was more than 16 inches long when it was recaptured about a year later, also in the Snake River.

Fast forward a few months to the spring of 2019, and the bull trout had made its way into the Imnaha River, where its PIT tag was picked up by a stationary detector. Messner said in a phone interview the fish was likely there to feed.

Bull trout, which are actually not trout at all but char, are predatory and feed on other fish. It’s not uncommon for anglers who hook a cutthroat or rainbow trout to sometimes have a bull trout pounce on their catch during the middle of the fight.

Because they are piscivorous, they have been compared to wolves by some anglers, who fear they can depress populations of other species.

When the bull trout was detected in the Imnaha River, its travels had only just begun. By July, the fish was detected in a small mountain stream in the Salmon River Basin. It was there to spawn, said Messner, and had covered 186 miles to reach its destination.

The fish was back in Hells Canyon last winter and returned to the Imnaha this spring. Messner wrote it’s likely the fish will return to its spawning grounds this month. He declined to name its natal stream, noting it is a bull trout spawning hot spot.

He said biologists have long known bull trout cover great distances as they move between overwinter habitat in places like the Snake River in Hells Canyon and the high mountain, natal spawning streams. But he said “we often don’t have documentation of that. That is why this one, in particular, is cool.” The practice of wintering in big rivers and spawning in higher, smaller streams is known as fluvial.

Bull trout were listed as threatened in 1998. Federal, state and tribal fisheries agencies are gearing up to conduct a status review of the species in Idaho, Washington, Oregon, Montana and a sliver of Nevada.

Idaho Department of Fish and Game biologist Brett Bowersox is leading the effort for Idaho. Bowersox said many of the PIT tag detectors, known as arrays, that have been placed in the beds of some mountain streams to track salmon and steelhead spawning are helping biologists keep tabs on bull trout as well.

“Idaho has some of the best bull trout habitat in their range as well as some areas that have challenges where management is trying to address those challenges and tackle them,” he said.

Barker may be contacted at ebarker@lmtribune.com or at (208) 848-2273. Follow him on Twitter @ezebarker.