Fish/Shellfish Research and Management - Fish/Shellfish Research
Date Published: October 2005
Number of Pages: 187
Author(s): Glen Mendel, Jeremy Trump, and Mike Gembala
This study began in 1998 to assess salmonid distribution, relative abundance, genetics, and the condition of salmonid habitats in the Walla Walla River basin within Washington.
Stream flows in the Walla Walla Basin continue to show a general trend that begins with a sharp decline in discharge in late June, followed by low summer flows and then an increase in discharge in fall and winter. Stream flows in the Walla Walla River have shown substantial increases in some areas in recent years. The increase is apparently associated with a 2000 settlement agreement between the U.S. Fish and Wildlife Service (USFWS) and the Irrigation Districts to leave minimum flows in the river.
Stream temperatures in 2004 in the Walla Walla River were similar to those in 2003. Upper montane tributaries maintained maximum summer temperatures below 65Â°F, while sites in the middle and lower Touchet and Walla Walla rivers frequently had daily maximum temperatures well above 68Â°F (high enough to inhibit migration in adult and juvenile salmonids, and to sharply reduce survival of their embryos and fry). High temperatures are possibly the most critical physiological barrier to salmonids in the Walla Walla basin, but other factors (available water, turbidity or sediment deposition, cover, lack of pools, etc.) also play a part in salmonid survival, migration, and breeding success. Increased flows in the Walla Walla River from the USFWS/Irrigation Districts settlement agreement, have not produced consistent improvements to stream temperatures.
Rainbow/steelhead (Oncorhynchus mykiss) trout represent the most common salmonid in the basin. Densities of Rainbow/steelhead in the Walla Walla River from the Washington/Oregon stateline to Mojonnier Rd. have increased since the USFWS/Irrigation Districts settlement agreement. In 2004, we switched to a new method of electrofishing in the Walla Walla River so direct comparisons with data from previous years could not be made, but densities are still considerably higher than before the USFWS settlement agreement. Other salmonids including; bull trout (Salvelinus confluentus), chinook salmon (Oncorhynchus tshawytscha), mountain whitefish (Prosopium williamsoni), and brown trout (Salmo trutta) had low densities, and limited distribution throughout the basin.
Steelhead spawning surveys were conducted on seven streams in the Walla Walla basin in 2004. Surveyors found 36 redds on Mill Creek, zero redds on Titus Creek, eight redds on Whiskey Creek and the Alyward Tributary, and 33 redds on the Coppei Creek system (15 on the South Fork Coppei, three on the North Fork Coppei, and 15 on the mainstem Coppei Creek). Bull trout spawning surveys in the upper Touchet River tributaries found a total of 93 redds and 127 live fish (71 redds and 71 fish in the Wolf Fork, 0 redds and 0 fish in the Burnt Fork, 22 redds and 56 fish in the North Fork Touchet, and 0 redds and 0 fish in Lewis Ck.). Numbers of bull trout redds and the number of live fish in the North Fork Touchet may have been affected by a siltation event in mid September from a construction project. Spring chinook spawning surveys were conducted in portions of the North Fork Touchet, Wolf Fork, and mainstem Touchet River in 2004, because 10 adults were seen at the adult trap in Dayton. No redds or adult spring chinook were seen during these surveys.
Recommendations for assessment activities in 2005 included:
1) reduce emphasis on stream flow monitoring because more gauges now exist in the basin and several years of data are now available from this project.
2) maintain temperature monitoring, but try to obtain more May temperature data; evaluate thermal barriers to migration in spring and fall.
3) reevaluate habitat inventory protocol and revise as necessary; try to get agreement with CTUIR regarding habitat inventory protocols and standards.
4) continue and expand habitat inventory and data use for EDT modeling.
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