OTTAWA — The federal government is calling a judicial inquiry into the disappearance of millions of Fraser River sockeye salmon in B.C.

Prime Minister Stephen Harper announced the news Thursday in the House of Commons, calling the salmon collapse a "serious matter."

"As the minister of fisheries and oceans has said on numerous occasions, we are very concerned about the low and falling returns of sockeye salmon in British Columbia," he said.

Trade Minister Stockwell Day, the regional minister for B.C., is to announce details of the inquiry Friday, including the judge who will head the probe.

There's been widespread alarm over the collapse of the multimillion-dollar sockeye salmon fishery on the West Coast.

The federal Fisheries Department estimated about 10.5 million sockeye would return to the Fraser River this year, but only a tenth that number has shown up.

The huge shortfall has forced the closure of commercial sockeye fisheries. It has also hamstrung aboriginal fisheries among Fraser River-based First Nations that depend on sockeye to supplement their diet over the winter.

Theories abound, ranging from warming water temperatures, new predators, changes to the food supply, sea lice from fish farms or, more likely, a combination of factors.