Experimental study of fish behavior near a tidal turbine model under dark conditions

Understanding the risk of collision between tidal stream turbines and marine species is required for environmental impact assessment. Field observations are often limited by sensor capabilities. This study used a laboratory-scale water tank to monitor fine-scale fish behavior near a model of rotating turbine blades. Differences in behavior between three species were investigated: Oryzias latipes, Gnathopogon elongatus, and Rhodeus ocellatus ocellatus. Behavioral response under dark conditions was further investigated for Gnathopogon elongatus, as it showed active behavior near the turbine under bright conditions. 71% of fish actively avoided or swam away from the turbine during bright conditions. Under dark conditions, 92% avoided or swam away; fish approached less frequently and retreated sooner than in bright conditions. Alertness in dark conditions possibly increases due to the inability of fish to visually detect the blades; thus, dark conditions may not be directly linked to a higher collision risk. No striking events occurred which resulted in injury or mortality.