VANCOUVER, British Columbia — The fate of wild salmon is a sensitive topic in the Pacific Northwest and arguments often end up in court in the United States, whether over threats to endangered fish by hydroelectric dams or sea lions swallowing them along their migration routes.

But on Thursday, a new and particularly bitter dispute began playing out in a very different kind of judicial venue across the Canadian border: a provincial Supreme Court justice held a hearing into questions of whether a potentially lethal virus had been detected in wild Pacific salmon — and whether the Canadian government was responding adequately.

The virus, infectious salmon anemia, has devastated farmed Atlantic salmon stocks in Chile and elsewhere. Some conservationists and scientists have long worried that the virus would spread from farmed fish to wild ones. Those fears escalated in October, when opponents of British Columbia’s ambitious farmed Atlantic salmon program, which is heavily promoted by the government, presented lab results they said showed an asymptomatic form of the virus in wild Pacific salmon.

Several more reports of the virus have emerged in the past two months, including a draft paper suggesting that the virus was detected as early as 2002 but not revealed by the government, further angering farming opponents.