No more Deschutes fish die-offs seen so far
Jul 25, 2015
Hot weather created hot water, spurring early July die-offBy Dylan Darling
The watch for sick or dead fish on rivers around Central Oregon continues as summer is expected to soon sizzle again.
Hot air temperatures in late June and early July triggered fish die-offs at the mouth of Deschutes River and along the Middle Fork of the John Day River. Fishing restrictions by the Oregon Department of Fish and Wildlife on some rivers and streams around the state, including the lower stretch of the Deschutes and much of the John Day River system, followed.
So far there have not been any more fish die-offs on the Deschutes, Rod French, Department of Fish and Wildlife district fish biologist in The Dalles, said Friday.
“Deschutes (River) temperatures have come down considerably,” he said.
Sweltering heat late last month and early this month left the Deschutes and Columbia River warmer than they are now.
“The Columbia reached 70 degrees at one of the earliest times on record,” French said. Water temperatures over 70 degrees can cause harsh conditions for fish.
Such was the case near the mouth of the Deschutes River, where the river flows into the Columbia. There dead and distressed sockeye salmon were found over the Fourth of July weekend. Days after the discovery, French went to investigate and counted 10 dead fish and 40 to 50 fish close to death.
He determined that columnaris — a naturally occurring bacteria worsened by high water temperatures — caused the death of the fish, which had been headed up the Columbia and swam into the Deschutes in search of cooler waters.
While there still are a few sick fish swimming around the mouth of the Deschutes, French said overall conditions have improved . The state Department of Fish and Wildlife reported a separate fish die-off, involving more than 100 chinook salmon, on the Middle Fork of the John Day River during the second week of July. Warm waters also contributed to the death of the fish.
Such die-offs have not been observed on the Deschutes and other waterways closer to Bend, said Brett Hodgson, district biologist for the Department of Fish and Wildlife in Bend.
“A lot of our streams in the Upper Deschutes have a lot of groundwater and spring influence,” he said.
The spring water may be as cool as 45 to 50 degrees, Hodgson said. “And that cool water carries quite a way downstream.”
As summer wears on the lingering question is whether high air temperatures will return.
For the short term, Central Oregon looks to be cooling down, said Mike Murphy, a National Weather Service meteorologist in Pendleton, but by the end of next week and into next weekend heat may come back.
“Into the mid-90s it looks like,” he said.
— Reporter: 541-617-7812,
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