The effect of energy turbines on the species composition of the fish community in the nearby environment of the turbine was tested using environmental (eDNA). Both turbines in the Marsdiep (Wadden Sea) and Lake IJssel were included. The turbines are expected to influence the behaviour of fish by either disturbance due to sounds or physical damage due to contact with the turbine.

The aim of this study

The foremost aim was to test whether the operation of an energy turbine affects the species composition of fish community in the nearby environment, whereby environmental DNA (eDNA) of fish during and after the operation of the energy turbine was taken as indicator for the presence and abundance of fish species.

The energy turbine are expected to influence the behaviour of fish in the close vicinity of the installation. Fish can either avoid the installation as a result of disturbance. However, fishes which do approach the turbine can get injured or killed, which might result in attracting predator species.

The energy turbine was situated in the Marsdiep tidal inlet between July 2015 until March 2016. At the start, a small turbine was installed and operated until October 2015 (mostly summer), whereas a bigger turbine was operational during January and February 2016 (winter). In order to measure the effects of the turbines, three assumptions were made:
1) the relative abundance of eDNA of a specific fish species represents its abundance (mass);
2) the year to year effects on fish community composition are subordinate to the effect of the turbine;
3) the turbine differently affects fish species featuring dissimilar ecological traits (i.e, demersal/pelagic, predator/prey).

The second aim was to test for the presence of three species of interest (Atlantic salmon - Salmon salar, European sea sturgeon – Acipenser sturio and European eel – Anguilla anguilla) near the discharge turbine at Den Oever in Lake IJssel.