A report that's expected to explain why and how millions of sockeye salmon vanished from B.C.'s Fraser River must be handed into the federal government next week, but it's still unclear when, or even if, the public will get to see a copy.

Under the terms of reference, B.C. Supreme Court Justice Bruce Cohen must deliver his report to the federal government by Monday.

"Our terms of reference only discuss the submission of the report, they don't discuss making the report public," said Carla Shore, commission spokeswoman.

"Our report goes to the government, and they then decided when or if to make the report public."

Melanie Carkner, a spokeswoman for Fisheries and Oceans Canada, said in an email to The Canadian Press the department wouldn't be commenting or providing interviews until the report was tabled.

But Ernie Crey, an adviser to the Sto:lo Tribal Council, said he's disappointed because the commission was a public and a judicial inquiry, noting he doesn't know why the report wouldn't be made public and provided to participants at the same time it goes to the government.

"There's no justification for them getting the report on Monday and excluding the public and the participants from having copies of that report," Crey said. "I can't think of a single reason that they could come up with to justify that."

Government is not in a position to change the report, he said.

"It's up to them to explain why they want to sit on it," he said.

Many deadline extensions

The federal government called the The Commission of Inquiry into the Decline of Sockeye Salmon in the Fraser River and appointed Cohen as commissioner in November 2009.

Just months earlier, about 10 million salmon were expected to return to B.C.'s rivers and streams, but only between 10 to 15 per cent of the fish actually showed up.

At the time, the federal government set a May 1, 2011 deadline for Cohen to submit his final report.

The inquiry began in August 2010 and ended in December 2011. It heard from 160 witnesses and compiled 14,000 pages of transcripts and 2,100 exhibits.

Deadlines were extended to June 30, 2012, followed by Sept. 30 and then Oct. 29.

The commission said on its website Cohen had requested the final extension to complete the writing, translation, and production of the report,

The report must be submitted in both official languages.

The proceedings cost about $26.4 million over three years, Shore said.