Canadian fisheries experts say they are extremely concerned by a steep decline in returning sockeye salmon numbers, and they are blaming climate change as the leading factor, Global News Canada reports.

Federal authorities have slashed their projection for the number of returning Fraser River sockeye in British Columbia to just over 600,000, compared with an earlier forecast of nearly 5 million fish.

It comes as the fisheries department releases a new report on the state of wild Pacific salmon.

This year has been an especially difficult year against the background of a decades-long decline in stocks, officials said.

The report cites increasing air and water temperatures in British Columbia and the Yukon region, changing precipitation patterns that alter freshwater habitats, as well as compounding effects of human activity.

Declines in the number of Pacific salmon stocks have prompted First Nations groups to call for a state of emergency to be declared.