Published 8:45 am Thursday, March 31, 2022
A cooperative effort has helped crews clearing portions of the Boise River avoid damaging spawning grounds for brown trout.
Boise River Flood Control District No. 10 maintenance crews avoided about 200 brown trout spawning areas, called redds, over a 16-mile stretch this winter as they cleared flow impediments ahead of irrigation season.
The district, with Boise Valley Fly Fishers and the Idaho Department of Fish and Game, last fall identified the redds and marked them using GPS technology. Volunteers scouted the river looking for them.
The district received recognition from the other partners in late March as maintenance season ended.
“It was a successful project because they missed 99% of the redds by knowing where they were,” Troy Pearse, Boise Valley Fly Fishers conservation director, said in a release. The workers, who often drive heavy equipment into the channel, “bent over backwards to make sure they didn’t harm the redds while doing winter maintenance work.”
Pinpointing brown trout redds is important because the species spawns in fall to produce fry that emerge in early spring — the same time district maintenance crews are at work. Brown trout make the spawning beds of small-diameter gravel.
Art Butts, Fish and Game southwest region fisheries manager, said the department appreciates the partnership.
“We’ve come a long way in the last 10 years when it comes to managing the Boise River in a sustainable way,” he said.
The district at the start of last year helped add gravel in some areas of the river to benefit fish. Pearse said in an interview that the recent work to mark brown trout redds should increase fry counts, which are often down in low-water years. Snow-water equivalent in the Boise River Basin tracked about one-third below normal in late March.
The district removes debris and makes repairs before flows increase for irrigation and other uses.
Crews in low-water years can cover more river miles in the service area, which runs from Garden City to Caldwell.
The work is performed under permits from the U.S. Army Corps of Engineers and Idaho Department of Water Resources, and a memorandum of understanding with the state Department of Environmental Quality.
“We work with partners on the river,” district Project Manager Mike Dimmick told Capital Press. “It’s easier when folks join hands.”
Pearse said protecting trout and habitat are critical as population growth increases fishing and other pressures. Naturally reproducing brown trout dominate a river stretch in the service area.
