Study finds salmon survival rates same with,
Breaching the Snake River dams won’t necessarily improve the
survival rate of chinook salmon, because returns of the fish
appear to be similar everywhere, including areas with pristine
freshwater habitats, a new study finds.
“Current efforts to conserve salmon populations assume that
restoring habitats modified by anthropogenic factors — e.g.
dams, dikes, forestry, road culverts, salmon farms in the
coastal ocean — will improve salmon returns and at least
partially compensate for worsening ocean conditions,” the study
“However, if survival also falls by roughly the same amount in
regions with nearly pristine freshwater habitats, it is
difficult to argue for a major role of regional factors in
causing the decline,” it says.
The study was published Oct. 30 in the scientific journal Fish
All chinook populations are likely being similarly affected
during their time in the ocean, because it is a shared
environment, author David Welch told the Capital Press.
“There are still some big puzzles here, because so little
research has gone on in the ocean,” Welch said. “For example, we
still don’t know how salmon migrate through the ocean or whether
different populations of the same species migrate to the same
area of the ocean.”
Welch is president of Kintama Research Services, a marine
environmental consultancy in Nanaimo, British Columbia.
Commercial catch data show various salmon populations are caught
in different regions of the ocean, but researchers have no idea
how they migrated there or how long or where they take up
residence during their two to three years in the ocean, Welch
Possible reasons for poor marine survival are likely multiple,
the study finds, with theories including growth, hatchery
practices, predation, competition, by-catch mortality in
fisheries and ocean conditions.
The theory that the dams result in poorer survival of Snake
River spring chinook relative to mid-Columbia chinook
populations after smolts migrate past the dams is specific to
the Columbia River Basin, the article states.
The theory still plays an important role in Columbia River
salmon management, but direct tests of the theory have not found
evidence to support it.
The decline of West Coast chinooks is still cause for concern,
“With the path many salmon populations are on, in terms of
falling marine survival, they may well be headed for
extinction,” he said. “This will cause all sorts of chaos
because, especially in the U.S., it is against the law — the
Endangered Species Act — to allow them to go extinct.”
Bureaucratic and legal systems may not be set up to deal with a
situation where key unknown problems are out at sea, while
institutional structures are set up to largely respond by
calling for more and more extreme responses in freshwater, he
Welch compared the situation to a doctor arguing for expanding a
patient’s lung capacity, when the patient has liver cancer. The
expanded lung capacity doesn’t address the cancer, he said.
“The situation with salmon is that we have a lot of people
trying to ‘fix’ possible problems in freshwater that they have
identified as being poor,” Welch said. “However, it is not at
all clear that freshwater conditions can be improved anywhere
near enough to compensate for the poor and still-worsening
survival at sea.”
Welch recommends chinook salmon advocates support efforts to get
to the root cause of the problems. They should insist on
“rigorous evaluation” of proposed fixes to make sure they are
actually going to be effective, he said.
The paper collated almost 2,300 years of survival estimates for
chinook salmon, Welch said.
The data represents the total number of years of sampling done
by government agencies on different Chinook salmon populations
that was available for analysis. As salmon survival worsened,
government agencies coastwide responded by adding more and more
populations to their monitoring efforts, Welch said. Essentially
all of them tell the same story of progressively worsening-and
similar- levels of survival, regardless of where the populations
originated, he said.
Similarly extensive monitoring programs are going on for coho
and steelhead, with other, less extensive monitoring programs
for sockeye, pink and chum salmon, Welch said.
“The big question is why, with all this monitoring effort, has
no one yet pointed out that survival was similar everywhere to
what was reported for the Snake River?” he asked. “The data is
all publicly available; it just took a lot of work to pull it
all together and show the obvious.”
Estimates of the survival of tagged adults returning to the
Columbia River failed to recognize that harvest in fisheries was
large and variable, which Welch considers “catastrophic” to
“It raises the broader question of whether the advocates for
extreme measures like dam breaching just have blinders on and
can’t really see what is going on,” he said.
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