July 29, 2007 in Outdoors

Levels dropping at Dworshak

From Staff, Wire Reports The Spokesman-Review
 

FISHERIES

John Day salmon perish

More than 100 spring chinook salmon have been found dead in the Middle Fork of the John Day River, apparently falling victim to high temperatures this month, the Oregon Department of Fish and Wildlife said last week.

Spring chinook salmon migrate to the John Day River in May where they rest in pools until they spawn in September.

Forty-one carcasses were found near the mouth of Big Boulder Creek and 62 were found at the mouth of Vinegar Creek, the ODFW said. Resident rainbow trout and mountain whitefish were also found dead.

It is common for some salmon to succumb to quickly rising water temperatures, but this year’s heat wave seems to have taken an unusually heavy toll, biologists said.

Many of the fish were believed to have died the first week in July when temperatures in the river climbed 8 degrees to 84 degrees, over the usual lethal limit for chinook salmon.

Dworshak Reservoir is helping Snake River salmon beat the summer heat wave.

Cool water released from the depths of Dworshak Reservoir on the North Fork of the Clearwater near Orofino allows fish managers and hydro-officials to hold temperatures downstream to help juvenile fall chinook migrants deal with the unnatural habitat created by Snake River dams.

State and federal fisheries officials attempt to keep water temperatures below 68 degrees at Lower Granite Dam. Higher temperatures threaten the vitality of the cold-water salmonids.

The first additional flows from Dworshak were released starting July 6. The effects were seen in water tempertures at Lower Granite about five days later because of the water travel time.

However, the water supply is dwindling and summer is only half over.

The Snake River basin snowpack was about 64 percent of the 30-year average. The Clearwater drainage is in slightly better shape, but upper Snake is very dry, with flows from Hells Canyon expected to be only 48 percent of normal, and quite warm, through September.

Those flows are also warmer than those from the Clearwater, contributing to the complexity of the temperature-control effort.

Releases from Dworshak eventually have a major impact on recreation at Dworshak Reservoir.

On Monday, the reservoir had been drawn down about 23 feet below full pool and was dropping roughly a foot a day. Nearly 100 mini campsites along the reservoir were still reasonably accessible, but they’ll require more effort to reach from boats as the level continues to drop.

The reservoir is likely to drop to about 80 feet below full pool by the end of August. However, in 1994, the pool was down to 104 feet below full pool by early August, eliminating access to many of the reservoirs recreation features.

Info: Dworshak Visitor Center, (208) 476 1255.

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