PARKER, E.*; KYNARD, B.; Conte Anadromous Fish Research Center, Turners Falls, MA and Univ. of Massachusetts, Amherst: Latitudinal Differences in Ontogenetic Behavior Between Two Populations of Shortnose Sturgeon: A Laboratory Study

Shortnose sturgeon (Acipenser brevirostrum) are diadromous sturgeons found in rivers along the east coast of North America from New Brunswick to Georgia. They are federally endangered throughout their range. Shortnose sturgeon life histories and adult behavior differ with latitude. Our objective was to determine if behavior of early life stages also differs with latitude. We reared fish from a northern (Connecticut River, MA) and a southern (Savannah River, SC) population of shortnose sturgeon from eggs and studied their habitat selection and dispersal behavior in laboratory tests. After hatching, during the period of yolk-sac absorption (free embryo life interval), fish from both populations selected cover under rocks, dark habitat, and black substrate. When fish began feeding exogenously (larva life interval), their behavior switched to preferring open, bright habitat, and white substrate. In an oval endless stream tank, Connecticut River fish moved downstream at night for 6 days (days 7�12 after hatching) beginning immediately after fish developed into larvae. Savannah River fish did not begin to move downstream in the stream tank until 10 days after becoming larvae (day 16 after hatching), and they continued to move downstream day and night without stopping for 4 months (at writing of abstract). The differences in dispersal timing and duration between the two populations likely reflect differences in habitat and selection pressures between the two rivers. Our data support the idea that shortnose sturgeon are locally adapted to particular rivers and conservation efforts should focus on restoring habitat and reducing anthropogenic impacts rather than stocking cultured fish into wild populations.