Stock Origin of Migratory Atlantic Sturgeon in Minas Basin, Inner Bay of Fundy, Canada, Determined by Microsatellite and Mitochondrial DNA Analyses

Five distinct population segments of Atlantic sturgeon Acipenser oxyrinchus were recently listed (April 2012) as endangered or threatened under the U. S. Endangered Species Act. Atlantic sturgeon are anadromous, spawning occurs in rivers from the St. Lawrence River, Quebec, to the Satilla River, Georgia, and subadults and adults undertake extensive coastal migrations. Bycatch of Atlantic sturgeon in coastal fisheries may have resulted in the slowed or failed rebuilding of many populations despite the imposition of a U. S. federal moratorium on their harvest in 1998. Canada's Bay of Fundy hosts weir and trawl fisheries which bycatch Atlantic sturgeon of unknown origin. Additionally, tidal power development projects for the Bay of Fundy have been proposed which could detrimentally impact migratory sturgeon. We hypothesized that the Atlantic sturgeon that occur in Minas Basin in the Bay of Fundy are of local Saint John River, New Brunswick, origin with little or no U. S. contribution. We used microsatellite DNA (11 loci) and mitochondrial DNA control region sequence analysis along with previously determined characterizations of nine reference spawning populations to quantify their stock origin. We determined that the summer assemblage of Atlantic sturgeon collected within Minas Basin was of mixed origin, with a greater than 60% contribution from the nearby Saint John River but with a substantial (34-36%) contribution from the Kennebec River, Maine, and a smaller (1-2%) contribution from the Hudson River, New York. There was significant genetic heterogeneity between smaller (<130 cm) and larger individuals (>= 130 cm) in Minas Basin; however, the smaller specimens were not exclusively of proximal Saint John River origin. Our results indicate that Atlantic sturgeon of U. S. origin are vulnerable to anthropogenic impacts in the Bay of Fundy, particularly those of Kennebec River origin.