Research Document - 2013/037
Recovery Potential Assessment for Atlantic sturgeon (Acipenser oxyrinchus) St. Lawrence Population: Habitat and Threats
By S. Dubé
Abstract
In May 2011, the St. Lawrence Atlantic Sturgeon, Acipenser oxyrinchus, population was assessed by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) as threatened. A recovery potential assessment (RPA) process was therefore set up by DFO Science in order to provide the information and scientific advice required to meet the various requirements of the Species at Risk Act (SARA). This research document provides general information about the preferred habitat and the potential threats to the St. Lawrence Atlantic sturgeon population. This population is distributed mainly from the St. Lawrence River, downstream from Trois-Rivières, to the Estuary and the Gulf of St. Lawrence. Six adult aggregation areas were identified during a telemetry monitoring, four in the fluvial Estuary (between Trois-Rivières and Quebec City) and two in the Upper Estuary ((downstream of Île d'Orléans). Three of the four freshwater aggregation areas (Richelieu Rapids, Saint-Antoine-de-Tilly and the mouth of the Chaudière River) were identified as potential spawning areas. The three other aggregation areas (Saint-Charles River estuary, Traverse du Milieu Channel and the northern channel between Sault-au-Cochon and Petite-Rivière-Saint-François) were identified as feeding and/or resting areas. The transition zone between fresh water and salt water in the St. Lawrence Estuary includes preferential benthic prey of Atlantic sturgeon and appears to be an important habitat for juvenile breeding and feeding. This habitat is strongly associated with the salt wedge boundary. The juvenile habitat was estimated at 76 km² and includes two main core areas of juvenile concentration located between the towns of Saint-Jean (Île d'Orléans) and Cap-Saint-Ignace. Potential threats to the St. Lawrence Atlantic sturgeon population include commercial fishery and habitat loss and/or degradation. The impact of dredging in the juvenile habitat remains a major concern. The acquisition of new knowledge about the Atlantic sturgeon habitat, in particular the precise location of spawning areas and the impact of certain threats is essential to the implementation of appropriate mitigation measures.
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