Impact of hydrokinetic turbines on rainbow trout behaviour

Hydrokinetic turbines are an emerging technology to supply reliable and renewable energy by harnessing kinetic energy from river or tidal flows. They are a potential alternative to current hydropower schemes that impound rivers, cause habitat fragmentation and fish mortality. To-date there is limited knowledge available about fish behaviour in the vicinity of hydrokinetic turbines and their effects on shoaling. In this study, juvenile rainbow trout (Oncorhynchus mykiss) were allowed to swim either individually or as a shoal of three fish in a laboratory flume with five turbine configurations of single and paired turbines. Results show the turbines did not reduce fish passage when in operation, and blade strikes were rare, none causing significant harm. Fish were more likely to swim in the turbine's downstream wake and upstream of the turbine (known as bow wake) when two turbines were operating because of the generation of larger areas of low velocity. Fish approached the turbines more often in shoals than alone and were overall bolder in shoals. This study suggests that hydrokinetic turbines do not significantly affect fish movement, thus supporting their utilisation as a suitable technology to extract renewable energy from rivers.