As demolition time draws near for the two Elwha River dams, 82
bull trout were recently captured in the middle portion of the
river and moved upstream out of harm’s way.
Bull Trout / Photo:
Olympic National Park
Scientists used their skills with hook-and-line fishing as well
as the more direct electroshock treatment to take adults and
juveniles from waters in and around Lake Mills at the upper Glines
Canyon Dam, as well as from the section of the river between the
The bull trout averaged 14 inches long, and some were as big as
The fish were held in net pens in Lake Mills for up to 10 days.
They were measured and sampled for genetic characteristics. Radio
transmitters were implanted in 31 fish to track their movements.
Then they were transported by helicopter to two locations upstream,
one near Elkhorn Ranger Station and the other at the mouth of Hayes
The protective action is considered important, because removal
of the Elwha and Glines Canyon dams is likely to dislodge an
estimated 24 million cubic yards of sediment that has collected
behind the dams since they were built, according to estimates by
the Bureau of Reclamation. Most of that sediment will come from a
delta at the south end of Lake Mills. Bull trout caught in the
sediment-laden river probably will not do well, researchers
“Using the best available science, we’ve taken steps to protect
the bull trout population and given them immediate access to
high-quality, pristine habitats in the upper river through this
relocation project,” said Sam Brenkman, fisheries biologist for
Olympic National Park.
According to the
“Bull Trout Protection and Restoration Plan” (PDF 1.6 mb),
turbidity will exceed 1,000 parts per million for extended periods
and may periodically exceed 10,000 ppm.
Even at 50 to 100 ppm, bull trout may stop feeding, suffer from
gill abrasion and experience stress that can reduce their fitness.
Greater levels of turbidity can lead to reduced health and possible
Bull trout were moved by helicopter
to the upper Elwha River. / Photo: Olympic National
It was assumed for planning purposes that fish remaining in the
river would die. That’s why a priority was placed on maintaining
access to high-quality areas upstream as well as tributaries and
off-channel areas that can serve as refugia from the murky
In addition, the demolition schedule includes “fish windows”
when construction will cease and the river will clear up to a safer
level, allowing for salmon and trout to migrate and spawn. These
fish windows are scheduled for November-December to aid coho and
chum migration into the Elwha; May-June for hatchery out-migration
and steelhead in-migration; and Aug. 1-Sept. 14 for chinook and
pink salmon in-migration.
Bull trout were listed as threatened under the Endangered
Species Act in 1999. Over the past five years, fisheries biologists
have surveyed the river to find out where the fish hang out,
tracked them with radio telemetry and conducted genetic studies to
understand their population dynamics.
Based on this work, researchers estimate the adult bull trout
population at less than 400 fish, less than 3 percent of the entire
Elwha River fish community. Between 60 and 69 percent are found
downstream of Rica Canyon, which lies just above Lake Mills.
Moving the fish upstream will allow them to find the most
suitable habitat following dam removal. A unique characteristic of
bull trout is that some individuals in a given population may
migrate to the ocean, while others stay in freshwater their entire
lives. Some may move into tributaries or lakes, while others prefer
the main river.
Biologists believe bull trout once occupied the entire Elwha
River system before the first dam was built in 1910. Following dam
removal, the landlocked population above the dams will be able to
move all the way downstream. The anadromous population that can’t
get above the Elwha Dam will be able to utilize the entire
The relocation effort fulfills a requirement of a 2000 revision
to the 1996 biological opinion for bull trout by the U.S. Fish and
“We are pleased that we met our objectives,” said Pat Crain,
fisheries biologist for Olympic National Park. “And this project,
designed to protect a threatened species, would not have been
possible without close collaboration among the various
“During two weeks of field work, more than 20 biologists — from
the U.S. Fish and Wildlife Service, U.S. Geological Survey,
National Oceanic and Atmospheric Administration, Lower Elwha
Klallam Tribe, Washington Department of Fish and Wildlife, and
Student Conservation Association — assisted with and monitored the
capture and relocation effort.”
The relocation work was completed June 17.
Other projects that should help bull trout include a culvert
replacement on Griff Creek, a middle tributary of the Elwha, and an
evaluation of the competition that occurs with nonnative brook
If you’d like to read more about the Elwha Dam removal, check
out the story I wrote for the
Kitsap Sun Sept. 4, 2010, or visit Olympic National Park’s
The tagging of captured bull trout
took place on Lake Mills. / NPS photo by John
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