Massive Oyster and Scallop Die-off in Canada: Cause is Unclear

The Globe and Mail has reported a "massive" die-off of Pacific oysters and Scallops in Canada has occurred. Growers and scientists are unclear what the cause may be. Some feel a combination of high commercial densities and a lower than normal algae bloom has stressed the shellfish, making them more susceptible to disease. Some feel ocean acidification is the problem. As with most things it is likely a combination of events which will ultimately be found to be the cause. Whatever those may be it is there should be concern about the larger integrity of the ecosystem of the Salish Sea, made up of waters extending from Puget Sound north to Vancouver Island.

From the article:

Over the past two years, Mr. Perreault’s oyster farm on B.C.’s south coast has experienced 80 to 90 per cent mortality of young shellfish – the normal attrition rate is 50 per cent – and last year, nearby Pendrell Sound had a massive die-off of wild oysters.
“It was in the billions,” he said of the Pacific oysters that died only a few months after they hatched.
“It’s hard to say without having somebody there monitoring what’s going on. It could be food related. Maybe there were too many oysters and there was not enough food and they just starved – or something else [is happening] in the water like the acidity level,” he said. “To be frank, we don’t know a lot about it and that’s what’s scary.”