Effect of the Horns Rev 1 Offshore Wind Farm on Fish Communities. Follow-up Seven Years after Construction Report commissioned by the Environmental Group through contract with Vattenfall Vindkraft A/S October 2011 Data sheet Title: Effect of the Horns Rev 1 Offshore Wind Farm on Fish Communities Follow-up Seven Years after Construction Editors: Simon B. Leonhard2, Claus Stenberg1 & Josianne Støttrup1 Authors: Claus Stenberg1, Michael van Deurs1, Josianne Støttrup1, Henrik Mosegaard1, Thomas Grome1, Grete Dinesen1, Asbjørn Christensen1, Henrik Jensen1, Maria Kaspersen1, Casper Willestofte Berg1, Simon B. Leonhard2, Henrik Skov3, John Pedersen2, Christian B. Hvidt4 & Maks Klaustrup2 Institutions: 1National Institute of Aquatic Resources, Technical University of Denmark, Charlottenlund Castle, DK-2920 Charlottenlund, Denmark 2Orbicon A/S, Jens Juuls Vej 16, DK-8260 Viby J, Denmark 3Danish Hydraulic Institute (DHI), Agern Allé 5, DK-2970 Hørsholm, Denmark 4NaturFocus, Lystrupmindevej 26, Vrads, DK-8654 Bryrup, Denmark Publisher: The Danish Energy Authority, Amaliegade 44, DK-1256 København K, Denmark Year: 2011 Version: 5 Report to be cited: Leonhard, S.B.; Stenberg, C. & Støttrup, J. (Eds.) 2011. Effect of the Horns Rev 1 Offshore Wind Farm on Fish Communities. Follow-up Seven Years after Construction. DTU Aqua, Orbicon, DHI, NaturFocus. Report commissioned by The Environmental Group through contract with Vattenfall Vindkraft A/S. Summary: The deployment of offshore wind farms is hypothesized to have a positive impact on fish communities. Increased habitat heterogeneity enhances species richness and abundance, and benthic fish communities may furthermore benefit from exclusion from trawling activities in wind farm areas. One of the world’s largest offshore wind farms “Horns Rev 1 Offshore Wind Farm” was analysed in a before- after-control-impact sampling design. Sampling included gillnet, grab and acoustics. Results of the studies are analysed and discussed in the report. Overall the study showed that fish communities varied significantly with season but that a distinct horizontal distribution and higher species diversity was found close to the turbines. Reef habitat species not previously recorded in the wind farm area were observed and species diversity increased. Sandeel assemblages typically found in sand bank areas like the Horns Reef were not impacted, although a short term increase in the abundance of greater sandeel was detected due to a temporary increase in juveniles in spring 2004. Cumulative effects of more wind farm development are also discussed in the report. Key words: Offshore wind farms, sandeels, fish communities, spatial temporal distribution, closed area effect, exclusion of fisheries, artificial reefs, cumulative effects, habitat suitability, Marine Protected Areas Cover photo: Sampling at Horns Rev. Claus Stenberg © Effect of the Horns Rev 1 Offshore Wind Farm on Fish Communities Contents 0 Summary ................................................................................................................ 3 Dansk resumé ............................................................................................................... 5 1 Introduction ............................................................................................................ 7 1.1 the Horns Rev 1 Offshore Wind Farm ................................................................... 8 1.2 Possible wind farm effects on fish communities ..................................................... 9 1.3 Possible effects on sand-dwelling sandeel assemblages ........................................ 11 2 Methodology ......................................................................................................... 13 2.1 Fish community. Used methodology .................................................................. 13 2.1.1 Fishing ..................................................................................................... 13 2.1.2 Test fishing .............................................................................................. 15 2.1.3 Hydro acoustic surveys .............................................................................. 16 2.1.4 Data analysis ............................................................................................ 17 2.2 Sandeel assemblages....................................................................................... 19 2.2.1 Data analysis ............................................................................................ 21 2.2.2 Sediment ................................................................................................. 22 2.2.3 Simulation of larvae drift for lesser sandeel and greater sandeel ..................... 23 2.2.4 Species distribution modelling ..................................................................... 23 3 Results ................................................................................................................. 25 3.1 Fish community .............................................................................................. 25 3.1.1 Community structure ................................................................................. 27 3.1.2 Abundance ............................................................................................... 29 3.1.3 Distribution in relation to distance from turbine foundations ........................... 37 3.2 Sandeel assemblages....................................................................................... 38 3.2.1 Day and night patterns .............................................................................. 40 3.2.2 Age ......................................................................................................... 41 3.2.3 Drift-simulation of greater sandeel and lesser sandeel ................................... 43 3.2.4 Sediment quality ....................................................................................... 45 3.2.5 Species distribution modelling ..................................................................... 46 3.2.6 Wind farm impact on the sandeel community ............................................... 46 4 Discussion ............................................................................................................. 48 4.1 Fish community .............................................................................................. 49 4.2 Sandeel assemblages....................................................................................... 51 4.3 Cumulative effects ........................................................................................... 55 5 Conclusions ........................................................................................................... 57 6 References ............................................................................................................ 58 Effect of the Horns Rev 1 Offshore Wind Farm on Fish Communities Appendix I ................................................................................................................. 2 Appendix II ................................................................................................................ 3 Appendix III ............................................................................................................... 4 Appendix IV ............................................................................................................... 5 Appendix V ................................................................................................................ 9 Appendix VI ............................................................................................................. 11 Appendix VII ............................................................................................................ 14 Appendix VIII ........................................................................................................... 16 Appendix IX ............................................................................................................. 21 Appendix X .............................................................................................................. 26 Effect of the Horns Rev 1 Offshore Wind Farm on Fish Communities Page 3 0 Summary Deployment of offshore wind farms is rapidly expanding in Denmark and in the rest of Europe, due to a high demand, both economically and politically, for renewable energy. At present 12 offshore wind farms are in operation in Danish waters. Offshore wind farms are often placed in relatively shallow waters (<20 m) due to engineering and economic constraints. These shallow areas are often biologically highly productive and function as important nursery and feeding grounds for a number of fish species. The establishment of wind farms is hypothesized to positively impact fish abundance and fish community structures by increasing habitat heterogeneity and through exclusion of trawling activities within the wind farm area. This report presents results from a field experiment in a demonstration study site (Horns Rev Offshore Wind Farm 1), one of the world’s largest offshore wind farms. The construction of this farm, which is composed of 80 wind turbines and located in the North Sea 14-20 km off the western coast of Denmark, at Blaavands Huk, was completed in late 2002. The aim of the study was to analyze changes in fish community structure, spatial distribution and changes in sandeel assemblages due to the establishment