Department of Fisheries (DFO) biologists have told a federal inquiry that fish samples, dating back more than two decades have tested positive for a virus potentially lethal to wild sockeye salmon — but that fact wasn't publicly reported.

Dr. Kristi Miller, the head of molecular genetics for DFO in Nanaimo, told the Cohen Commission on Thursday that frozen samples dating back to 1986 have been tested, and show infectious salmon anemia (ISA) has been in B.C. waters for at least 25 years.

The public inquiry into the decline of the Fraser River sockeye salmon stocks was extended for three extra days after ISA was detected in wild B.C. salmon two months ago by Simon Fraser University Prof. Rick Routledge.

That revelation put the Canadian Food Inspection Agency and B.C.'s fish farming industry on high alert, but those results couldn't be confirmed and government scientists announced earlier this month that extensive testing came up negative.

The alleged presence of ISA in B.C. salmon stocks is controversial because the virus had never before been found in salmon off B.C.'s coast, either in the Atlantic species that are farmed in ocean pens or in B.C.'s indigenous wild salmon.

The virus is known to be devastating to farmed Atlantic salmon and opponents of the fish farm industry have suggested farmed fish could spread ISA to wild stocks, with catastrophic results.

The virus has been linked to the destruction of the salmon farming industry in Chile and Europe.

The crisis has prompted the Canada Food Inspection Agency to develop a regular surveillance program for ISA, that is expected to be in place as early as next spring.