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9/22/2006
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An adult female salmon deposits
eggs in nesting pockets of shallow
water in the Santiam River of Western
Oregon. - Mark Rozin/Capital Press |
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Heat threatens hardy salmon
More energy spent waiting for lower
temperatures means less energy to spawn
By PHIL WRIGHT
East Oregonian Publishing Group
It may be hard to believe that chinook salmon
or steelhead could be bothered or hurt by a
few degrees warmer water.
After all, chinook are survivors, making their
way down rivers and through dams until they
reach ocean, where they grow big enough to
avoid predators and mature. Then they make the
arduous journey upriver to spawn.
Steelhead are just as tough. Idaho steelhead
have been found south of the Kamchatka
Peninsula in Russia. That's about 4,000 miles
from fresh water. Add another 900 to 1,000
miles of rivers and streams to that, and the
upper migration limit stretches to about 5,000
miles.
But something as seemingly innocuous as a few
degrees of temperature change in the Columbia
River and its tributaries has significant
effects on anadromous fish such as salmon and
steelhead.
Temperature readings taken by the U.S. Army
Corps of Engineers at the Bonneville Dam
starting in 1938 reveal a gradual warming of
the Columbia River. When the Corps began
recording the water temperature there, the
average water temperature was about 65 degrees
Fahrenheit. But in 2005, the average water
temperature was about 69 degrees.
Four degrees over a course of more than 60
years may not see like much. But according to
the federal Environmental Protection Agency,
68 degrees is the upper limit for salmon
migration.
Scientists are noticing changes in salmon
migration because of that warmer water.
Kyle Dittmer is a meteorologist and
hydrologist for the Columbia River
Inter-Tribal Fish Commission (CRITFC). He's
also the president of the Oregon Chapter of
U.S. Meteorological Society. Climate change is
here and more is on the way, he said.
"It's like a freight train coming, and no one
can stop it," he said.
That freight train already seems to be hitting
fish in the Columbia River. Dittmer said
changes in water temperatures trigger spikes
in fish migration and traffic jams of fish as
they try to pass through the dams. Those
spikes haven't been seen before.
Don Chapman has been a fisheries biologist for
more than 50 years. He acknowledges he's no
climatologist, but he knows fish and his
analysis concurs.
Chapman said salmon and steelhead are
displaying the influence of climate change in
their migration patterns.
Fall chinook are delaying in the mouths of
cool Columbia River tributaries like the
Klickitat, the Deschutes and the Big White
Salmon. And they are taking longer to reach
spawning grounds.
The fish wait in those pockets in late August
or September for water temperatures in the
main stem of the Columbia River to drop enough
so they can continue along.
While they wait, salmon are not simply resting
and summoning energy. Just the opposite is
happening.
"Once they start migrating from the estuary,
they don't feed," Dittmer said. "So any delay
means less energy they will have to spawn."
As temperatures continue to rise, those
migration patterns will shift still further,
Chapman said, and the summer migrations will
be hurt the worst. This includes summer
steelhead, juvenile fall chinook moving
downstream and adult chinook and sockeye
moving upstream. Those summer migrants are
either going to change habits and move earlier
or later, or they will disappear, Chapman
said.
"That's the prognosis," he said.
Not just the dams
Chapman also said examining a regression on
Columbia River water temperatures reveals a
significant upward trend that is not caused by
dams. He said the Fraser River, which isn't
dammed, has risen 1.5 degrees Celsius. The
Fraser River is the largest river in British
Columbia, beginning near Mount Edith Cavell in
the Rocky Mountains near Mount Robson and
entering the Pacific Ocean at Vancouver, B.C.
- some 870 miles away.
Chapman said dams are not the culprits causing
increasing temperatures, but rising air
temperatures in the Columbia Basin and in
other basins are responsible.
Warmer water delaying migration isn't the only
problem salmon face as the climate changes.
Dittmer said redds - salmon eggs - develop
during the course of winter, but the baby fish
are incubating faster and are emerging
earlier, in late February or March, because
they are accumulating heat from water. That
early emergence could mean food sources may
not be present.
"That could affect the whole balance," Dittmer
said.
Chapman explained that predator fish - pike,
shad, carp, small and large mouth bass - that
feed on smolts are non-native, warmer water
fish, while native salmon are a cooler water
fish. The predator fish could easily increase
with warmer water, pressuring the salmon still
further. These predator fish also have a
higher metabolism, and as water temperatures
increase, so do their appetites. And smolts
are a favorite food.
The warmer water adds stress to the smolts,
Chapman said, and that makes them easier prey
and increases their risk of disease.
Out at sea may not be much better. Increasing
temperatures suggest a reduction in plankton
and phytoplankton, the food young salmon eat
at the mouth of the Columbia River.
"The moral for fish is grow or die," Chapman
said. "When you get a year of poor offshore
conditions, particularly in the first six
weeks as fish hit the sea, you get poor
survival."
Looking to the long term
Dittmer said the Inter-Tribal Fish Commission
has been conducting a long-term climate change
study concerning average flows through river
basins in Oregon and Washington. The study
revealed that in every basin, flows are
peaking sooner and are reduced compared to
years past. Spring and summer flows go down
just at the time salmon migrate.
"Every basin I've looked at is impacted,"
Dittmer said. The Umatilla and Walla Walla
basins have been hit the hardest.
In the Umatilla Basin, the flow on average is
peaking 16 days earlier compared with 100
years ago. The Walla Walla Basin, though, has
the largest shift, with 161/2 days.
The average median - the half-way point in
peak flow - has shifted and is now coming
sooner.
Dittmer said all the research along the West
Coast indicates more runoff is being shifted
to autumn and winter from spring and summer.
And again, the Umatilla and Walla Walla basins
are taking the biggest hit, having dropped by
25 percent.
Dittmer said spring-summer flows only drop by
10 percent when you adjust for 70 years of
impact from the dams.
So again, the dams can't be blamed.
Chapman said the net result of what climate
change means for salmon is still unclear, but
he anticipates the whole southern boundary of
salmon and steelhead will move northward.
And that means the Columbia River, once the
world's richest salmon fishery, won't be as
hospitable to salmon as it once was.
Another view
But not everyone has a view quite so
pessimistic.
Gary James, fisheries manager for the
Confederated Tribes of the Umatilla Indian
Reservation, said climate change now isn't
having a major impact on salmon recovery and
salmon runs.
"Environmental conditions have always
fluctuated," he said.
James said habitat degradation is what needs
to be dealt with because of its effect on
salmon.
"There's degradation in tributaries, but
mainly, the worst impacts are on the main
stem, where our river is turning into a series
of reservoirs and there're still pretty poor
passage of anadromous fish out there."
James seems to agree, however, that climate
does play a role in the life of already
stressed fish.
"Without man's mortality there used to be a
lot of flexibility. The salmon runs could take
a lot of environmental flux. Now all those
other man-caused killers have pushed salmon
sometimes to the edge of the cliff, and
sometimes you'll see a bad climate or ocean
year really take a hit on salmon."
But again, he said, climate change isn't the
only cause, but because the fish are stressed
"they don't have the breathing room or the
flexibility to absorb the environmental
fluctuations."
Dittmer also said salmon are a resilient fish,
and people have it in their power to continue
and to accelerate endeavors that will help to
enhance the natural defense system, by
restoring stream beds, planting trees along
river banks, and creating curves within the
river, among other projects.
But Dittmer said Americans need to think
large-scale and long-term when it comes to
restoration and conservation efforts.
"We need to have a Manhattan-style project as
soon as possible," he said.
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