 |
| ODFW fish biologists (left to right) Rob Dietrich, Todd Alsbury, and Danette Faucera, run a sein net through the Sandy River to collect spring Chinook for two years after Marmot Dam was removed, and a fish trap at the facility was also destroyed. Later on, ODFW used portable weirs to do this job as fish management evolved. (ODFW file photo |
Ten years after Oregon’s largest dam removal, salmon and steelhead rebounding on the Sandy
Thursday, October 19, 2017
CLACKAMAS, Ore. – Ten years ago a new era of salmon and
steelhead recovery quite literally started out with a bang when Marmot
Dam was removed from the Sandy River.
More than a ton of high-grade explosives were detonated, taking off the face of the 47-foot high concrete dam.
At the time, it was the largest dam breach ever attempted.
Portland General Electric, owner of the dam, figured it would be more
cost-effective to remove the structure than upgrade it to meet new
federal re-licensing standards.
In July 2007, in a highly publicized event, PGE blew the
concrete face off its dam on the Sandy River. For the next three months,
large backhoes with pneumatic hammers pulverized, drilled, pulled apart
and hauled off the remaining pieces of the dam. On Oct. 19, a rainstorm
swept away the backfill that had accumulated behind the dam, making the
Sandy totally free-flowing again,...
...from its headwaters on Mt. Hood to its confluence with the Columbia River in Troutdale 56 miles away.
...from its headwaters on Mt. Hood to its confluence with the Columbia River in Troutdale 56 miles away.
Biologists, conservationists, anglers, and others hailed the
removal of Marmot Dam as a victory for imperiled native runs of Chinook
and coho salmon and steelhead. The hope was that fish would benefit
from better flows, better water quality and unrestricted access to prime
spawning grounds in the uppermost reaches of the river.
So has 10 years of a free-flowing Sandy River been good for fish?
The answer is an unqualified ‘yes’, according to Todd
Alsbury, ODFW district fish biologist for the Sandy, and one of the
partners in the removal of Marmot Dam.
Now, for the past three years, when other runs of salmon and
steelhead around the region have been down, the Sandy has been seeing
increasingly strong returns; in some cases, double what they were a
decade ago before Marmot Dam was removed.
“While not solely due to dam removal, returns of wild spring
Chinook, winter steelhead, and coho have increased significantly as
compared to their abundance before the dam was removed,” said Alsbury,
who noted that in the 10 years since Marmot Dam was removed ODFW has
observed the largest returns for all three species in the 40 years.
For example, the number of wild spring Chinook increased
from an average of 809 before dam removal to 2,086 afterwards.
Similarly, coho increased from 784 returning fish before dam removal to
1,959 afterward, and wild winter steelhead increased from 898 to 2,757.
To really gauge how successful removal has been, though, it
helps to look at how the fish were doing prior to removal of the dam.
Wild spring Chinook were nearly extirpated in the 1950s and
’60s by dam operations, habitat losses, and other human impacts. During
this period, fishery managers tried to rebuild the population with
hatchery Chinook, which were intercepted in a trap at Marmot Dam and
trucked to Sandy Fish Hatchery, where the next generation of fish was
spawned and reared.
However, fisheries management changed dramatically in 1998
when the fish were listed as threatened under the Endangered Species
Act. This triggered discussions about ways to recover the fish,
including by taking out Marmot Dam and reducing releases of hatchery
fish so there would be fewer of them to compete with the ESA-listed wild
fish. These discussions also led to one of the first integrated brood
programs whereby wild spring Chinook were reared at the hatchery, and
later cross-bred with hatchery Chinook to create a fish closely
resembling the native fish, instead of looking outside the basin for
replacement stock with different genetics.
When Marmot Dam was removed, ODFW biologists lost a fish
trap that gave them the ability to catch and separate wild fish. The
fish needed to be separated so the wild ones could go on upstream to
spawn while the hatchery fish were captured and taken to the hatchery to
spawn. For the first two years after dam removal, ODFW staff netted
brood stock out of the river using large seine nets pulled by swimmers
in full wetsuits. Later on, biologists installed weirs, or portable
traps, in the river for this purpose.
To continue providing a recreational fishery, Alsbury and
his staff developed an acclimation site to rear and release juvenile
fish at a location that is suitable for returning adult fish. They now
collect adult fish using temporary weirs near the release location to
capture returning adults. Afterwards, the weir can be removed from the
river.
“Our goal is to first protect native runs of native salmon
and steelhead while at the same time providing a robust recreational
fishery,” said Alsbury. “Thanks to a lot of hard work on the part of
many dedicated individuals and a lot of collaboration we are starting to
see some impressive results.”
“Habitat is the key,” Alsbury added, noting that the Sandy
is one of the few rivers where fish habitat is now being added faster
than it is being degraded or lost, and that salmon are now showing up to
spawn in habitat that didn’t exist before.
