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Smolt/Adult
Monitoring: Deschutes River
Location:
At the south end of
Puget Sound, near the mouth of the Deschutes River, at Tumwater Falls
Park, Tumwater, Washington.
History:
Prior to the construction
of three fishways in 1954, the falls at the mouth of the river presented
a complete barrier to fish passage. To support commercial and recreational
fisheries, the (then) Washington Department of Fisheries began planting
hatchery chinook and coho into the Deschutes system in 1946, and from
1949-1953, returning adults were trapped at the entrance to Capitol Lake
and transported to a release point above the falls to spawn naturally.
Steelhead trout have been planted into the river since 1933, and cutthroat
trout were planted from 1933 through 1980. The coho and cutthroat runs
are currently sustained by natural production in the river.
In 1961, two large
adult holding ponds were built at the upstream end of the uppermost fishway
to retain migrating adult chinook for enumeration and egg collection.
The WSPE began enumerating returning adult coho and evaluating coho smolt
production from this system in 1976.
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Methods:
The downstream-migrant
trap is positioned at the base of the lower falls, in an area of
high velocity, providing sufficient flow and depth for trap operation.
WDFW used a scoop trap from 1977 through 1990. This trap was replaced
with an 8-ft diameter screw trap in 1991, which we continue to operate.
From 1977 through 2000, the trap was fished from dusk through dawn
each night throughout the April to mid-June trapping season, except
during large hatchery releases or high flow events. In 2001, we
expanded our trapping season from February through the end of June
to incorporate chinook evaluation. Trap operation was extended
to 24-hours day to assess chinook production. Captured wild coho
smolts are coded-wire tagged before release.
Adult trapping
begins in September, when the first chinook arrives, and continues
through the coho run (late-December). All fish are captured in
the holding ponds. Coho are examined for coded-wire tags, and tags
are removed from a portion of the recovered fish. After counting
and sampling, all species are released into the river through the
bypass chutes, except for a portion of chinook required to meet
hatchery needs. The ability to capture 100% of returning adults
(and thus, the coded-wire tags) enables us to accurately measure
smolt-to-adult survival, and to assess the environmental factors
affecting wild salmon populations in South Puget Sound.
Available
Publications & Data:
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