Sockeye salmon spawning on the rivers and streams of Washington state, British Columbia and southeastern Alaska have been producing fewer and fewer adults over the last six decades, a new study suggests.

In one dramatic example, the Fraser River’s early Stuart sockeye run produced 20 adults for every spawning sockeye during the 1960s, but productivity had dropped to about three adults per spawner by the mid-2000s, said Randall Peterman, co-author of the study and a professor at Simon Fraser University in Burnaby, B.C.

Around Washington state, British Columbia, and eastern Alaska, the story’s been much the same, with some populations dropping below the replacement ratio of one adult per spawning salmon, he added.

The topic known as productivity — which is measured by the number of adults produced by each spawning salmon — is addressed in a paper published today in the Canadian Journal of Fisheries and Aquatic Sciences.

“People who rely on salmon for their livelihoods, or their First Nations food and social and ceremonial purposes, really find sockeye populations very valuable, and so it’s important to keep them going at a productive level,” said Peterman who conducted the research with post-doctoral fellow Brigitte Dorner.

“Furthermore, there are very strong and important concerns about the long-term viability of many sockeye populations as well as other salmon populations, other species.”

Since sockeye salmon are adaptable, their declining productivity may suggest that something is going wrong in the ecological system, he added.