A new study reports that 24 out of 37 sockeye salmon populations from Washington State to southeast Alaska showed a decrease in productivity over the last 20 years.
More depressing news for sockeye salmon lovers: dramatically fewer adult sockeye have been produced in the rivers and streams of Washington state, BC, and southeastern Alaska over the last six decades.
A large new study, originally produced for the Cohen Commission (a federally appointed inquiry into the decline of Fraser River salmon stocks) and published today in the Canadian Journal of Fisheries and Aquatic Sciences, finds the declining stocks are not unique to the Fraser River, but are much wider in scope than originally anticipated.
Rapid and consistent decreases
The study found that there have been “rapid and consistent decreases” in sockeye salmon productivity in stocks between Puget Sound in Washington state to Alaska’s Yakutat peninsula. In fact, over the last 20 years, 24 out of 37 populations of salmon showed a decrease in productivity.
In one example, the Fraser River’s early Stuart sockeye run declined from 20 adults per spawning adult in the 1960s to three by the mid-2000s. And in many areas throughout the study boundaries some populations dropped below the replacement ratio of one adult per spawning salmon.
Cause still unknown
Though the paper didn’t address the causes of the declines, the large “spatial” trends suggest some causes are more likely than others, according to the researchers. One unlikely cause is small-scale disturbances such as habitat destruction, because the decrease has happened simultaneously over pristine as well as disturbed habitat.
Randall Peterman, co-author and professor at Simon Fraser University, says the large area of the trends “… seems to suggest that the causal agents are more likely either pathogens, predators, or reduced food supply. Could be one or all of those.”
Will we ever find out?
Peterman credited the success of the analysis to researchers in the past who were given the budget to do “diligent monitoring” from 1950 through the 2000s. “I want to emphasize that the current budget-cutting environment that we\’re in, in government, is not conducive to understanding what the causes are of these changes,” he said.