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.
