MONTREAL (AFP) - Canada launched a judicial inquiry Friday into why millions of Pacific salmon failed to reach Canadian rivers some months ago, in a bid to salvage the stocks that could shake up domestic fishery policies.

Bruce Cohen, a justice on British Columbia's Supreme Court, was appointed commissioner by International Trade Minister Stockwell Day for the inquiry into the decline of sockeye salmon in the Fraser River.

Cohen's report may lead to "recommendations for improving the sustainability of the sockeye salmon fishery ... including, as required, any changes to the policies, practices and procedures of the Department of Fisheries and Oceans," said the prime minister's office in a statement.

The report is set to be submitted by May 1, 2010.

Canada's Department of Fisheries and Oceans had projected that between six and 10 million sockeye salmon would return to the Fraser river in a peak August run.

Only a fraction showed up and where the others went remains a mystery.

A record number of salmon smolts were born in the Fraser in 2005 and migrated to the ocean. Nature dictates that most of them should have returned by now to spawn.

The initiative, announced Thursday by Prime Minister Stephen Harper, has been welcomed by the fishing industry.

"It is very big news because I do not know of any government anywhere in the world that appointed a judicial inquiry to look at its government's management of the fishery," Phil Eidsvik, spokesman for the British Columbia Fisheries Survival Coalition, told AFP.

"Most government's, including all of Canada's previous governments, did their best to cover-up and hide their mismanagement of the fishery," Eidsvik added.

The inquiry may help prevent the industry in Canada's westernmost province from going the way of Atlantic cod, whose stocks collapsed in the early 1990s following over-fishing, said Eidsvik

Officials and ecologists speculate the salmon could have been affected by warmer ocean temperatures, fewer food sources, or more prey.

Alternately, they may have contracted sea lice or other infections from area fish farms, or the fisheries department's complex forecasts may be flawed.

"Honestly, we don't know what happens to them when they go out into the ocean," Stan Proboszcz, a fish biologist from the Watershed Watch Salmon Society, told AFP in August.

"There's a myriad of factors that could explain what's going on," he said.