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 65°F,
while sites in the middle 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). 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.
