Prineville, OR. Between June 16 - 20th ODFW used a method known as electrofishing on the crooked river to gather samples of redband trout and mountain whitefish. During that time biologists removed stunned fish to record size, condition, and abundance of these species. Once the survey was complete the fish were released unharmed, however there have been some reports in the fishing community that dead fish have been seen throughout this section of the river. There's no direct correlation as to how the electrofishing method impacts fish, but that's of no consequence at this point - early reports show that the number of redband trout is on the decline.
According to guide feedback posted by The Fly Fisher's Place, the average number of trout per mile has decreased from nearly 5,000 to only 400 trout per mile. These numbers are astounding - it's unbelievable that a once great fishery has been reduced so drastically. It's likely that the resulting decline in trout population is due to the management of Bowman dam by the Bureau of Reclamation. The Crooked River is well known for it's varying water levels and it's major impact on the fish below the dam.
The biggest threat to trout populations isn't that fish are being killed by their travel through the dam, but unmanaged water levels builds Bubble Gas Trauma (BGT) inside fish below the dam. Atmospheric gases naturally diffuse between air and water to reach an equilibrium of pressure. These gases then dissolve in the blood of fish, like all aquatic animals, as a natural process. When water is suddenly warmed, gas bubbles form in the fish's blood and leads to stress or even death. This process is known as supersaturation and unfortunately, it's what's reducing the numbers of trout in this section of the river.
We'll have to wait for the results to be posted on the ODFW website, but based on initial estimates it doesn't sound like there is a lot of hope for redband trout in this section of the river anytime soon.