Abstract
The automated analysis of nearly three weeks of multibeam hydroacoustics data identified nearly 35,000 tracks of fish passing a tidal turbine in the East River, New York. These tracks included both individual fish and schools during periods with the turbine absent and present, operating and not operating, and during all phases of the tidal cycle, ebb, flood, and slack. The density of fish in the sampled area when the turbine was absent was roughly twice what it was when the turbine was in place, both when rotating and when not rotating. This suggests that some avoidance may be occurring before fish are close enough to the turbine to be observed by the DIDSON. Various measures of swimming behavior (direction, velocity, and directness) were calculated for each track and evaluated for indication of behavioral responses to turbine presence and operation. Fish tracks were grouped based on tidal cycle, current velocity, and swimming direction and evaluated with respect to turbine presence and operation and with respect to distance from the turbine. A multivariate statistical analysis (Canonical Discriminant Analysis) found significant differences among groups with respect to turbine presence and operation suggesting that some fish respond to the turbine by adjusting swimming behavior. Analysis of individual metrics revealed similar findings. Our analysis suggests that fish might be making small adjustments to swimming direction and velocity as they pass near an operating turbine. However, large adjustments in swimming direction or velocity were not observed, and we do not believe that the presence of the turbine interrupts in any significant way the normal movements of fish through the area.