I recently wrote about how the beginning of irrigation season can be lethal to fish and gave an example of Three Sisters Irrigation District abruptly de-watering part of Whychus Creek last month, killing spring chinook smolts being prepared for release into the creek. Yesterday I accompanied a local agency employee to the acclimation tank to take a look.

The photo above shows the tank next to a side channel of Whychus Creek where smolts are “acclimated” prior to being released into the creek. The idea is to imprint this water on the smolts so they will return to Whychus Creek as adults in approximately two years. In the foreground is the pump which draws water from the creek. The pump supplies water through a steel pipe to the far end of the tank and water is returned to the creek through the white PVC pipe at the near end. After a period of acclimation, typically a couple of weeks, a screen at the front of the PVC pipe is removed and the fish move into the creek. This is the beginning of their journey down Whychus Creek to the Middle Deschutes and then hopefully all the way to the Columbia River and the ocean.

Below is a photo of the pump and the creek. The water was lowered to a point where the pump no longer functioned. Of course, the water in the tank continued to flow out. Needless to say, a tank with no water is not good for fish. The Upper Deschutes Basin anadromous fish reintroduction effort uses various types of acclimation facilities in locations near the Metolius and Crooked Rivers, but this is the only one on Whychus Creek.

Yesterday the tank was full again and steelhead smolts were being acclimated. Hopefully, Whychus Creek will continue to flow at a level that will keep the tank full. As always, I learned something new when spending time with a local fish biologist. The steelhead smolts mostly looked identical to small trout. Some, however, had small silver colored patches on their skin. I thought this might be a sign of disease but was told that those fish were starting the process of “smoltification”. As you may know from inadvertently catching one, smolts have a silver or steel skin color. I had assumed that the entire fish would slowly change color, not have it occur in patches.