By BROOKE SNAVELY
CENTRAL OREGON DAILY NEWS
Wickiup Reservoir dropped to zero percent capacity this fall, turning what was the largest freshwater lake and one of the best fishing spots in the upper Deschutes Basin, into a mere creek flowing through its original channel.
“Once they get down to zero storage in Wickiup those fish have two options: Some of them migrate upstream in the old Deschutes River channel. A good percentage of them are leaving through the unscreened outlet at the dam,” said Brett Hodgson, fish biologist for the Oregon Department of Fish & Wildlife, Deschutes District. “We are trying to identify relative numbers and species composition of the types of fish that are leaving the reservoir and entering the river.”
Biologists use an electrofishing cata-raft to survey the fish in the Deschutes River below Wickiup Reservoir.
An oarsman maneuvers the boat while two biologists scoop fish that are temporarily stunned by a 300-volt electrical current.
“Once we get them in the net, we transfer them to a live well in the middle of the boat and we keep them there as we continue to sample as we move downstream. We are constantly monitoring the condition and health of the fish in the live well. Once we get it full and need to process the fish and get them out of there, we pull into the shore. Collect biological data off of them, identify species and length of the fish.”
The captured fish are checked to see if they’ve been previously tagged with passive integrated transponders, the same kind of microchip that some people place in their pets to help reunite them with their owners if they get lost.
“The reason why we are tagging these fish is as we do follow up sampling next spring, next fall, whenever we do it, we will check the fish we capture in these follow up events to see whether they have a tag in them or not. This gives us ideas about survival rates, growth rates and movement of fish in the system. Get a lot of information off the fish in a little microchip.”
Although they’ve been capturing and tagging fish in the river for five years, biologist Brett Hodgson says it’s too early to draw conclusions about how fish populations are responding to changes in water management, such as this year’s emptying of Wickiup Reservoir.
“When we did this effort in 2018 in the fall, we captured a lot of rainbow trout. When we came back the following spring and sampled the same area, almost all those fish were gone. Did they move into other areas or were they not able to survive the low winter flows? It’s probably a combination of both.”
One thing that’s evident is Mountain Whitefish are the dominant species in the upper Deschutes River. Hodgson says these native fish seem better able to adapt to fluctuating river flows caused irrigation releases in summer, and low flows in winter when water is stored in Wickiup Reservoir.
“In the case of the rainbow, our past monitoring that we did previous to the low reservoir events in 2018 & 2020, there were virtually no rainbows in here. I can say with a lot of confidence that the rainbow we are encountering today came out of the reservoir.”
Hodgson says there are good numbers of German brown trout in the river, probably a mix of resident fish and those that left the reservoir.
“From a fish management perspective, you can look at it two ways: The brown trout and rainbow trout that are leaving the reservoir, obviously that is negatively affecting the fish in the reservoir. Those fish are no longer accessible to anglers in Wickiup. However, they are a source population to establish a fishery in the upper Deschutes.”
The fish that drop out of Wickiup Reservoir into the river need more water to survive. Help may be coming through the Deschutes Basin Habitat Conservation Plan.
“One of the elements in the habitat conservation plan is a schedule for improving flows in the upper Deschutes. I think the initial target is 300 cubic feet per second and it goes up from there. The sooner we get to 300 CFS, the better it will be for restoring a rainbow trout population and a quality fishery in the upper Deschutes River.”
Other less desirable fish, including bass and brown bullhead catfish, are also being pulled out of the reservoir. These species could displace the native fish. They may also pose a threat to the endangered Oregon Spotted Frog which is one of the native species driving the habitat conservation plan.
“Whether it’s the habitat conservation plan and submitting comments or just as people are conversing among themselves, if there’s general interest in protecting and maintaining and restoring the environment up here, decision makers and managers will respond to that. It’s the public will.”