International eel symposium, 2003 - Quebec August 11, 2003
Oral Presentation

Three-Dimensional Movements and Behaviors of Silver-Phase Migrant American Eels at a Small Hydroelectric Facility

Brown, L.S.* S.O. Conte Anadromous Fish Research Center, Biological Resource Discipline, U. S. Geological Survey, Turners Falls, MA.
Haro, A. S.O. Conte Anadromous Fish Research Center, Biological Resource Discipline, U. S. Geological Survey, Turners Falls, MA.
Castro-Santos, T. S.O. Conte Anadromous Fish Research Center, Biological Resource Discipline, U. S. Geological Survey, Turners Falls, MA.

Presenter email address: leah_brown AT usgs.gov

Abstract Text: Hydroelectric facilities have historically presented migratory challenges for diadromous fishes, restricting their ability to continue upstream and/or downstream movements where dams have been constructed. The impacts of hydroelectric facilities on the distribution and abundance of the American eel, Anguilla rostrata, may have significant effects on their recruitment, population, and reproductive success. An array of eight acoustic receivers was deployed in the forebay of a small hydroelectric facility, Cabot Station, on the mainstem of the Connecticut River in Turners Falls, Massachusetts. Twenty silver-phase migrant American eels were intercepted at the Holyoke Dam during the fall of 2002, surgically implanted with PIT tags and acoustic transmitters, and released 1.5 km upstream of Cabot Station. Data were analyzed to evaluate eel movements in three-dimensions relative to depth and selection of passage routes at various operating conditions. Downstream movements and residence behaviors of 18 out of 20 eels were detected within the acoustic array and routes of passage were determined. Three-dimensional tracks for each eel released and detected in the acoustic array were reconstructed; 96% of detections occurred during periods of twilight or during the night. Eleven percent of eels implanted with PIT tag transmitters were detected using the surface bypass system at Cabot Station as a route of passage and at least 67% passed through the turbine intakes. Twenty-eight percent of the eels were observed re-entering the acoustic array on multiple dates before downstream passage occurred through the turbine intakes.