Assessment of Salmonids and Their Habitat Conditions in the Walla Walla River Basin within Washington: 2002 Annual Report

This study began in 1998 to assess salmonid distribution, relative abundance, genetics, and the condition of salmonid habitats in the Walla Walla River basin.

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. Manual stream flow measurements at Pepper bridge showed an increase in 2002 of 110-185% from July-September, over flows from 2001. This 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 the Walla Walla basin were similar to those in 2001. Upper montane tributaries maintained maximum summer temperatures below 65 F, while sites in mid and lower Touchet and Walla Walla rivers frequently had daily maximum temperatures well above 68 F (high enough to inhibit migration in adult and juvenile salmonids, and to sharply reduce survival of their embryos and fry). These 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. The increased flows in the Walla Walla, due to the 2000 settlement agreement, have not shown 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. dropped slightly from 2001, but are still considerably higher than before the 2000 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. A large return of adult spring chinook to the Touchet River drainage in 2001 produced higher densities of juvenile chinook in 2002 than have been seen in recent years, especially in the Wolf Fork. The adult return in 2002 was substantially less than what was seen in 2001.

Due to poor water conditions and trouble getting personnel hired, spawning surveys were limited in 2002. Surveyors found only one redd in four Walla Walla River tributaries (Cottonwood Ck., East Little Walla Walla, West Little Walla Walla, and Mill Ck.), and 59 redds in Touchet River tributaries (10 in the North Fork Touchet, 30 in the South Fork Touchet, and 19 in the Wolf Fork. Bull trout spawning surveys in the upper Touchet River tributaries found a total of 125 redds and 150 live fish (92 redds and 75 fish in the Wolf Fork, 2 redds and 1 fish in the Burnt Fork, 0 redds and 1 fish in the South Fork Touchet, 29 redds and 71 fish in the North Fork Touchet, and 2 redds and 2 fish in Lewis Ck.).

A preliminary steelhead genetics analysis was completed as part of this project. Results indicate differences between naturally produced steelhead and those produced in the hatchery. There were also apparent genetic differences among the naturally produced fish from different areas of the basin. Detailed results are reported in Bumgarner et al. 2003.

Recommendations for assessment activities in 2003 included:

1) continue to monitor the Walla Walla River (focusing from the stateline to McDonald Rd.), the Mill Ck system, and the Little Walla Walla System.

2) reevaluate Whiskey Ck. for abundance and distribution of salmonids, and Lewis Ck. for bull trout density and distribution.

3) select or develop a habitat survey protocol and begin to conduct habitat inventory and assessment surveys.

4) summarize bull trout data for Mill Ck, South Fork Touchet, and Lewis Ck.

5) begin to evaluate temperature and flow data to assess if the habitat conditions exist for spring chinook in the Touchet River.