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 o felectrofishing in the Walla Walla River
so direct comparisons with data from previous years could riot 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.
