Fish distributions in a tidal channel indicate the behavioural impact of a marine renewable energy installation

Shaun Fraser,Benjamin J Williamson,Vladimir Nikora,Beth E Scott

doi:10.1016/j.egyr.2018.01.008

Shaun Fraser, Benjamin J Williamson + Show 2 more

Open Access

https://doi.org/10.1016/j.egyr.2018.01.008

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Journal: Energy Reports	Publication Date: Feb 20, 2018
Citations: 29	License type: cc-by

Affiliation: University of Aberdeen

Abstract

In the dynamic environments targeted for marine renewable energy extraction, such as tidal channels, the natural distribution of fish and behavioural impacts of marine renewable energy installations (MREIs) are poorly understood. This study builds on recent methodological developments to reveal the behaviour of fish schools using data collected by a seabed-mounted echosounder deployed in extreme tidal flows and in the wake of a MREI (composed of the foundation of a full-scale tidal stream energy turbine). The results show a significant change (p<0.001) in the vertical distribution of fish schools in the vicinity of a MREI compared to a nearby control location representative of the natural conditions. The MREI is associated with an overall increased rate of fish school observations (+74%), particularly at night (+163%) and in the MREI wake flow (+378%), related to the disruption of natural diurnal behavioural patterns in school characteristics (size, relative density, and distance from seabed). These results indicate an attraction effect of the MREI, and show that the aggregation and vertical distribution of fish in the modified flow conditions is dependent on tidal phase with evidence of avoidance of the MREI depth range during peak flow velocities. The behavioural responses observed in this study provide new information relevant to the environmental impact assessment of marine renewable energy developments and highlight priorities for further research.

Highlights

In recent years there have been rapid developments in the extraction of tidal stream energy with numerous marine renewable energy installations (MREIs), including full-scale tidal stream turbines, deployed around the world (Zhou et al, 2017)
A total of 523 fish schools were observed in the presence of the MREI, and 396 fish schools observed in the control location representative of the natural conditions
Flood and ebb results are similar in the control and not significantly different (p = 0.89); while a clear and significant (p = 0.02) difference between flood and ebb results is apparent in the presence of the MREI and dominated by the increase in fish school observations in the wake flow

Summary

Introduction

In recent years there have been rapid developments in the extraction of tidal stream energy with numerous marine renewable energy installations (MREIs), including full-scale tidal stream turbines, deployed around the world (Zhou et al, 2017). The potential behavioural impacts of MREIs could result from direct interaction of mobile animals with devices, or over larger scales due to the hydrodynamic consequences of changes to the natural flow structure with unknown ecological implications (Shields et al, 2011). Recent field observations around marine renewable energy devices have focussed on fish interactions with turbine components at very fine scales using optical (Hammar et al, 2013; Broadhurst et al, 2014) and acoustic (Viehman and Zydlewski, 2015) cameras. Previous field observations have been limited in the depth range or temporal coverage available, for example by excluding data from the upper part of the water column (Viehman et al, 2015) or during slack conditions (Shen et al, 2016)

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