A controversial new study is challenging long-standing science that pins salmon declines in the Snake River Basin on dams and is roiling the already rough waters of fish recovery.
The work by British Columbia scientist David Welch puts the blame for poor returns of adult Snake River spring and fall chinook salmon on conditions in the Pacific Ocean instead of the dams and argues chinook runs from California to Alaska have suffered similar declines. Some salmon researchers are skeptical of that conclusion and say the effects of dams can’t be dismissed.
Welch’s work, funded by the Bonneville Power Administration and published in the journal “Fish and Fisheries,” argues since chinook runs in rivers with pristine freshwater habitat and those with highly degraded habitat have suffered similar declines, the problem must be in the ocean.
Welch and his colleagues looked at data from chinook runs up and down the west coast of North America and worked to establish and compare smolt-to-adult return rates for each of the runs. The rate is the measure of the number of juvenile chinook that leave a river system to spend two to three years in the ocean and ultimately survive and return to freshwater. In the Columbia River Basin, salmon managers believe a rate of 2 percent is required for chinook runs to hold steady and 4% to 6% is needed for runs to grow. However, rates are often 1% or less.
Welch and his colleagues found since the late 1970s, chinook returns have generally declined by about two-thirds in much of the study area and that survival of chinook that return to the Snake River is nearly identical to survival of those that return to undammed rivers in the Puget Sound.
“At the broadest level, the major implication of our results is that most of the salmon conservation problem is determined in the ocean by common processes,” they wrote in the paper.
“Attempts to improve (smolt-to-adult return rates) by addressing region-specific issues such as freshwater habitat degradation or salmon aquaculture in coastal zones are therefore unlikely to be successful.”
Welch also said the results undercut the theory that many juvenile Snake River salmon and steelhead perish in the ocean from stress and injuries they incurred while passing dams, a phenomenon known as delayed mortality. He also said scientists that back delayed mortality have erred by not accounting for harvest in their survival models.
Efforts to recover the fish should concentrate on the ocean and not on freshwater, Welch said.
“I’m not looking to stir the pot for no reason. I think there are some serious public policy questions here,” he said. “The first one is are we even going in the right direction with management of salmon, and I’m not convinced we are. I’m deeply concerned we may well be on the wrong path.”
The study is being trumpeted by supporters of the four lower Snake River dams and critiqued by salmon advocates and some scientists who have long argued the dams should be breached.
The Northwest River Partners, a hydropower industry group, issued a news release about the study and has written a letter to the governors of Idaho, Washington, Oregon and Montana to make sure they are aware of it as they prepare to begin collaborative discussions on salmon recovery in the Columbia River Basin. Kurt Miller, executive director of the group, argues the Snake River dams should be retained as a key tool in moving toward a carbon-free energy portfolio in the region.
“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,” Miller said in a news release. “This conclusion means that our carbon-free hydropower resources are more important than ever.”
But the work is expected to be challenged by other researchers. The Fish Passage Center at Portland is formally reviewing the work, and other researchers are looking at it as well. Charlie Petrosky, a retired Idaho Fish and Game research biologist who has written several papers on delayed mortality, said he has many concerns with Welch’s work. Petrosky thinks the study sets up a false dichotomy between freshwater and the ocean.
“All of the studies I have been involved with show (smolt-to-adult return rates) are a function of both,” he said, noting there is ample evidence the Snake and Columbia dams have a negative impact on salmon and steelhead.
“There is undoubtedly very broadscale ocean patterns – warming oceans – that are definitely not good for survival,” he said. “But to brush off the effects of what happens as fish are migrating through an altered system I think is very misleading.”
Petrosky questioned how Welch and his team compared survival rates between river systems, noting the data is collected in different ways and may not be comparable. He also disputed that he and other researchers failed to account for harvest.
Michele DeHart, of the fish passage system, said boosting survival of juvenile salmon in fresh water is critical regardless of ocean conditions. For example, she said if ocean conditions are really bad, the best response is to take steps to ensure as many juvenile fish reach the ocean in good conditions as possible. The same applies when ocean conditions are good, she said.
Welch said he expects and welcomes scrutiny.
“If you come up with credible scientific analysis that shows why we are wrong, the science advances and my reputation takes a bit of a hit because I missed something rather obvious.
“But when the dust settles, we still need to manage salmon populations into the future.”
The study is available at bit.ly/2IjasmB.
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