The potential for artificial reefs effects in offshore windfarms to support coexistence with fisheries

Abstract

In response to rising greenhouse gas emissions and increasing energy demands offshore wind developments are proliferating globally. The total capacity of offshore wind energy, which is currently 64 GW, is projected to increase by 380 GW in the next decade. These developments result in various direct and indirect impacts on the marine environment and other maritime industries. In particular, offshore wind farm development can lead to reduced fisheries access and negatively impacts stocks of species that support fisheries. Artificial reef effects arising from the addition of artificial hard substrates into soft sediment habitats are accepted as the most profound environmental impacts of offshore wind farm development. This process alters community composition and is associated with an increase in economically important species within offshore wind farms. As such, it has been suggested that artificial reef effects may support the coexistence of offshore wind farms and fisheries. However, there is a limited empirical basis to understand how this process supports the presence of economically important species and how these species interact with offshore wind farm related infrastructure. Furthermore, artificial reef effects are expected to vary as a result of sitespecific characteristics which is likely to lead to variation in the fishing opportunities arising from particular sites. This thesis focuses on enhancing our existing knowledge of artificial reef effects within offshore wind farms with a specific emphasis on economically important species. It aims to address gaps in our understanding of factors driving the presence of economically important species within offshore wind farms, species-specific interactions and behaviour, as well as investigating the site-specific factors that contribute to the variability in artificial reef effects. The movement patterns, residency, and habitat use of the European lobster (Homarus gammarus) and Ballan wrasse (Labrus bergylta) in association with offshore wind farm related infrastructure were investigated to highlight species-specific interactions and determine the factors driving the presence of these species within offshore wind farms. Results indicated that both of these species strongly associated with the offshore wind farm infrastructure and highlighted that increased shelter afforded by offshore wind farm infrastructure is likely a key factor in their presence at these sites. However, these results also underscore that the factors driving the presence of certain economically important species are species-specific. The relative abundance and diversity of macrofauna, including economically important species in relation to different wind farm features were also examined. These results reveal that the presence of certain structures within offshore farms, in particular scour protection, creates a suitable habitat for a range of fisheries relevant species and therefore has the potential to increase fishing opportunities within offshore wind farms. Together, the results presented throughout this thesis highlight that artificial reef effects taking place within offshore wind farms support the presence of economically important species and as such should be considered for future offshore wind developments in order to facilitate the coexistence of offshore wind farms and fisheries.

Date of Award	2023
Original language	English
Awarding Institution	Aberystwyth University
Supervisor	David Wilcockson (Supervisor)