Cold tailwaters below dams sometimes provide trout fishing opportunities where there would otherwise be none. And being able to regulate flow levels gives fishery managers unique advantages to improve fisheries.
One advantage is to control stream flow out of a dam. Often, flows are turned up to flush sediments that have collected between gravels and cobble, habitats used by trout for spawning. Cleaner cobble means better spawning success.
Until now, fishery managers weren’t exactly sure if turning up the flows flushed more than sediment. Juvenile rainbows, with less developed muscles and swimming power especially in winter, could be washed away, too, thus defeating the purpose.
But now we know that’s not the case, at least according to scientists at the Wyoming Cooperative Fish and Wildlife Research Unit in Laramie.
In the Big Horn River below Boysen Dam, 17 rainbow trout were planted with radios in the late autumn, then followed then the next spring when flows were turned up about eight times higher.
Remarkably, none of the young fish moved downstream. In fact, three rainbows moved upstream, but none over a 100 yards away from their pre-flushing flow home. Large boulders that created slow-water pockets provided refuges for young fish in higher flows.
Controlling the flow of streams results in better habitat for trout.
While the fishing may be not so good in a torrent intentionally sent downstream, it’s all for the better. The result is better spawning habitat without hurting the existing population. And we know just how important in-stream cover is, such as boulders, for trout.
When not penning stories about the outdoors, Craig works in communications for the U.S. Fish and Wildlife Service. He is an outdoors’ columnist for the Albuquerque Journal and ESPN Outdoors, and a frequent contributor to Flyfisher and North American Fisherman magazines. He holds degrees in fisheries and wildlife management from Hocking College and New Mexico State University, and an M.Sc. in fisheries science from the University of New Mexico. He’s a candidate for an M.A. in rhetoric and writing at the University of New Mexico. He writes weekly for sportsmansguide.com.