Migration of Landlocked Atlantic Salmon Smolts and Effectiveness of a Fish Bypass Structure at a Small-Scale Hydroelectric Facility

Abstract

Downstream movements by smolts of Atlantic salmon Salmo salar were monitored with radiotelemetry to assess the effectiveness of an angled trash rack and fish bypass structure at a small hydroelectric dam on the Boquet River, New York. Telemetry of 170 Atlantic salmon smolts and visual observations of stocked smolts were used to determine aspects of migration behavior. Smolts began mass migrations after river temperatures reached or exceeded 10°C. Many radio-tagged smolts interrupted movements upon reaching ponded waters or the dam. River flow did not affect the frequency of migratory movements, dam passages, or rate of movement (P > 0.05). Migrations lasted approximately 30 d. Passages at the dam occurred primarily at night (61%); diurnal passages (17%) and crepuscular passages (17%) were of secondary importance, and timing of 5% of the passages was undetermined. All passages were through the bypass or over the spillway when angled trash racks were in place. Six passages occurred when trash racks perpendicular to the penstock were in place; three of these were penstock passages. The angled trash rack and bypass structure significantly reduced entrainment through the penstock and turbine (P < 0.05).