fish habitat 12.23

This debris flow in the Frank Church River of No Return Wilderness is being pushed downhill toward the river where it is expected to help improve fish habitat.

Natural processes in two of Idaho’s wilderness areas are improving habitat for salmon and steelhead, Idaho Fish and Game Fisheries Biologist Eli Felts says.

In the 3.5-million acre Frank Church River of No Return Wilderness and the Selway-Bitterroot Wilderness areas hundreds of miles of highly productive spawning and rearing habitat for multiple fish species exist, Felts said.

“Habitat restoration is a big part of enhancing wild salmon and steelhead in Idaho,” he said. “This work often occurs in areas where the landscape and streams have been negatively affected by human activities.” That’s not the case in the two wilderness areas, though, he said. “A large part of Idaho has been set aside to do its own thing.”

While the wilderness areas were used for grazing and mining in the past, they’ve been left alone for many decades, he said. The Selway-Bitterroot was designated wilderness in 1964 and the Frank in 1980.

When left to its own devices, nature tends to make native fish habitat thrive, Felts said. One of the best ways that happens is through debris flows, which typically occur for several years following a wildfire. The dead trees fall to the ground and are moved downhill by floods and avalanches, piling up into “flows,” Felts said.

“Over time large flows of dead trees push their way toward the main tributaries and rivers where fish spawn and rear,” he said.

Once the debris flows reach the stream “they have a big positive influence on the habitat,” he said. Large pieces of wood provide hiding spots for fish to avoid predators, places to rest during migration and feeding areas. Large log jams also redirect and slow rivers down. As flows change course, deep pools often form, providing habitat for fish. The wood debris also traps sand and fine gravel, vital for spawning areas.