Anadromous Sturgeons: Habitats, Threats, and Management

<em>Abstract</em>.—Space use and habitat selection of early juvenile Atlantic sturgeon <em>Acipenser oxyrinchus</em> have been little studied and remain largely unknown throughout the species’ range. In 2000–2002, survey trawling, ultrasonic telemetry, benthos sampling, and hydrodynamic modeling were used to determine the summer movement patterns, home range size, and habitat use and selection of early juvenile Atlantic sturgeon in the St. Lawrence estuary. Sonic-tagged Atlantic sturgeon, assumed to be age 2 based on their size, used a global area estimated at 76 km2 that included two main core areas. Individual summer home range sizes varied from 1 to 8 km2, but core areas were generally smaller than 1 km2. The mean daily distance traveled ranged from 0.4 to 13.5 km/d and was significantly related to sturgeon size. Fish were located mostly in freshwater relatively close to the salt wedge boundary and far from the shore, intertidal zones, and islands. They mostly used the 6–10-m depth range relatively close to a channel, in areas with low bottom current velocities, and over silt–clay substrates. Salinity and distance from the salt wedge were the two most important variables explaining their habitat selection. Age-0 Atlantic sturgeon used similar depth ranges, bottom salinities, and current velocities, but occupied mainly sandy substrate. Management implications of these results are discussed in relation to the impact of dredging and sediment disposal operations in the St. Lawrence estuary.