Abstract
Anadromous Atlantic sturgeon (Acipenser oxyrinchus) occur in most large rivers and in the sea of Atlantic Canada. They are recorded as far north as George River, Labrador, but spawning is unknown north of the St. Lawrence River. In Canada, spawning is in freshwater, usually close to tidehead, during June-July. To maintain a population, this iteroperous species requires access to rivers with medium to large estuaries and the sea. Juveniles inhabit the mesohaline region of estuaries (5–25 ppt salinity), usually over a mud-sand bottom. After 1–12 years, they migrate to sea where they spend another 5–10 years before reaching sexual maturity, after which they return to rivers to spawn every 1–5 years depending on sex and latitude of the natal stream. Migration is extensive, north and south on the Atlantic coast, and seaward to the edge of the continental shelf. There are five known spawning populations in Canada and probably numerous unknown ones. Spawning populations in the United States occur from Maine to Florida and into the Gulf of Mexico. Populations of A. oxyrinchus in Europe are extinct. The size of Canadian populations is unknown but recent studies suggest there are 500+ adults in the St. Lawrence River. In Canada, Atlantic sturgeons are fished commercially and catches of 20–140 metric tons have been taken annually during the last 20 years in the St. Lawrence and St. John rivers.