Although Canada's coastline is extensive and contains many diverse molluscan species, the resource is economically relatively small. In 1995 nearly 200 000 t valued at $114.5 million were taken. Scallops and clams from the Atlantic coast were the dominant species, accounting for 69% by weight and 85% by value of all molluscs from both coasts. There is no molluscan fishery in arctic waters. In Canada most molluscs are fished rather than cultured. For most species the short growing season results in growth rates too slow for profitable culture. Oysters and mussels are the only species now cultured in some quantity. Expanded production of both is possible but, in general, the potential for molluscan aquaculture in Canada is not great.
The occurrence of paralytic shellfish poison can limit the use of some species. The toxin derives from poisonous planktonic dinoflagellates on which bivalves feed. Although harmless to molluscs, it can be fatal to humans. Also fatal is the toxin domoic acid which caused a ban on Atlantic shellfish in late 1987 after 100 people became ill and at least 2 died after eating poisoned mussels from Prince Edward Island. Except for scallop and partially for squid, most species are fished for or cultured by individual fishermen or families. Native people fish certain species (eg, clams) commercially and for food. Federal and provincial governments participate in regulation as well as controlling factors such as sanitation, pollution, lands and marketing. Jurisdictions differ from province to province as a result of agreements developed through the years.
Scallops are fished by vessels 20-30 m long, pulling drags over the bottom in depths up to 100 m. The centre of the fishery is on Georges Bank, ownership of which was contested by Canada and the US until October 1984, when the International Court at The Hague awarded the easternmost one-sixth, rich in scallops and groundfish, to Canada. It is unlikely that production can be increased beyond the level of past catches. Only the adductor mussel is used, sold fresh or frozen. On the Atlantic coast, oysters are cultured in shallow waters below the low-tide mark. Oyster ground is leased from the federal government and planted with oyster seed collected by various means. Oysters are marketed in the shell, usually by the dozen, and are eaten raw.
On the Pacific coast the oyster industry uses a Japanese species that normally grows in intertidal areas. These zones are leased from the provincial government. Oysters are shelled and sold by volume of meat. Clams occur in both intertidal and subtidal areas and are fished by hand and by mechanical harvesters. Some are sold fresh but most are canned.A number of commercial species occur on both coasts and the fishery is regulated by season, quota or size. Abalone live in rocky subtidal areas of the Pacific coast and are fished by divers. The catch is regulated by size and area quota. Most abalone are sold frozen to Japan. The centre of squid production is Newfoundland where they are fished by jigs and nets. Squid are used for bait and exported to Japan for food.