Central Oregon's Crooked River has all the trappings of a flyfishing utopia, complete with a rugged Wild and Scenic stretch that back in 2013 held as many as 4,000 redband rainbows per kilometer. As of today, however, its booming trout population has gone bust. Biologists are also saying 'goodbye' to its once prolific whities. 

As stated in a new report from Oregon Department of Fish and Wildlife, in just one year the estimated density of Crooked River redband trout dropped 87 percent to just 185 fish per km in 2016—the lowest ever recorded—in the stream’s most productive section from Bowman Dam downstream toward Prineville.

Authors of the report link the Crooked's native fish collapse to a couple of obvious (and, yep, preventable) factors: winter river flows reduced to a trickle, coupled with a gas bubble disease caused by the total dissolved gas produced at the BLM-operated Bowman Dam. Moreover, a low winter discharge of 35 cubic feet per second for 50 days, a high spring discharge greater than 600 cfs for 44 days, and freezing temperatures during the low flows, plus a high level of dissolved nitrogen during the high flows, helped trigger the massive die-off.

Reintroduced anadromous fish populations, including steelhead, were not directly sampled. But, no surprise, with similar habitat and biological requirements their populations would likely experience the same detrimental effects.