(VANCOUVER, WA) - - Newly published research has unveiled remarkable insight into the survival rates of Chinook salmon populations along the North American West Coast, highlighting a dramatic omission in the way such data has been interpreted for over two decades.
The peer-reviewed research entitled, "A Synthesis
of the Coast-wide Decline in Survival of West Coast Chinook Salmon” has
been published by the leading science journal, Fish and Fisheries.
The research was carried out by a team from Kintama Research,
led by the award-winning Dr. David Welch, who
has been involved in marine research on salmon for 40 years and recognized
globally for his work.
Importantly, this pivotal research comes at a
time when many interest groups continue to press for the removal of productive,
cost-effective hydroelectric dams, despite the region’s aggressive carbon
reduction goals. Many believe that the federally-operated dams are preventing
the recovery of threatened and endangered salmon populations - specifically in
the Snake River, the largest tributary of the Columbia in the Pacific
Northwest.
However, Dr. Welch’s research questions that
conclusion. The study reveals that Chinook salmon survival has fallen by
two-thirds, on average, for almost all regions along the western coast of North
America - in both dammed and undammed areas - and not just in the Columbia
River Basin.
The study is supported by deep technical and
scientific analyses of the extensive survival data collected by government
agencies over many decades. The research also reveals that survival is
indistinguishable for Puget Sound and Snake River spring Chinook populations,
despite the absence of major dams in the Puget Sound region.
The implication of the research is that the
shared ecosystem of all Pacific salmon, the Pacific Ocean, is likely the source
of the coastal-wide decline in Chinook salmon populations. Dams, while having
some effect on salmon survival, do not appear to be a key limiting factor for
recovery.
Harvest Omitted
Dr. Welch’s scientific analysis also found a
significant flaw in the models used to produce adult survival estimates for the
Columbia River Basin salmon. The two predominant models used to formulate
regional salmon policy both rely on PIT tag data--small RFID tags implanted in
some fish, which only track salmon when they swim past in-river receivers.
Adult salmon caught in fisheries in the ocean or
river are not counted by these monitoring systems, meaning that harvest is
ignored in the models. The assumption by the modelers is that harvest is
insignificant and stable from year to year, so excluding it isn’t a
problem.
In contrast, Dr. Welch’s research found that
harvest of Columbia River Chinook stocks can be large--as much as 75% of the
total salmon run for some Columbia River populations--and highly variable over
time.
This finding means that the predominant models
fail to recognize that the reason for good or bad salmon returns may have been
strongly influenced by how a range of US federal, state, and Canadian agencies
were regulating the adult salmon catch.
As a result, the model outcomes are
unintentionally providing erroneous information.
This new research clearly shows a need to revise
the models and, ultimately, salmon policies themselves.
No Evidence for Delayed Mortality
Those who oppose hydroelectric dams with advanced
fish passage systems often refer to the theory of delayed mortality. This
assumption is rooted in the unproven idea that juvenile salmon are injured by
successive dam powerhouses and fish bypass systems, reducing their survival in
the ocean.
However, Dr. Welch makes a convincing case that
there is no real evidence for delayed mortality in the data. He provides solid
reasoning, using data from both the Fish Passage Center and other independent
datasets, that greater dam passage does not usually cause lower survival rates.
This finding is critical, because policies based
on the delayed mortality theory have cost the region billions of dollars and
increased our carbon footprint without addressing the real issues leading to
lower salmon survival--climate change and warming oceans.
The governors of Oregon and Washington both
recently pointed to the region’s devastating and deadly wildfires as signs that
climate change will continue to have a very negative effect on Pacific
Northwest communities. Dr. Welch’s study shows that they should be similarly
concerned about the oceanic impacts of climate change and their effects on
salmon survival.
This conclusion means that our carbon-free
hydropower resources are more important than ever.
