Abstract
Sharks and rays play pivotal ecological roles in marine ecosystems, and globally, 32.6% of shark, ray and chimera species are considered to be threatened with extinction. Yet impacts of offshore infrastructure on sharks and other elasmobranchs are often poorly understood or overlooked. Large-scale development of the offshore wind farm (OWF) industry is planned for Australian waters, which are home to an estimated 314 species of sharks and rays. Here we apply a precautionary environmental risk assessment framework based on the hierarchical productivity-susceptibility approach, aiming to estimate the magnitude of OWF impacts on sharks and rays, and to identify knowledge gaps. Of 314 species considered, 39 species were considered to be of potential concern. These species were progressed to a semi-quantitative productivity-exposure (Level 2) assessment for seven offshore regions around Australia and for the areas currently designated for OWF development. Input parameters in the Level 2 assessment included life-history, movement, behaviour and physical habitat attributes. These attributes were assessed for direct and indirect impacts to provide a vulnerability rating. At a regional level, electromagnetic fields and secondary entanglement were identified as the main potentially negative impacts, whereas altered food chains, increased food availability through artificial structure and protection from fishing interactions were identified as potentially positive impacts. At the level of OWF designated zones, electromagnetic fields, habitat alteration, barriers to movement and secondary entanglement were identified as the key potential negative impacts. Species-specific research and impact mitigation may be required for higher-risk species, such as the great hammerhead and the oceanic whitetip, in addition to medium-risk species including the scallop hammerhead and white shark. For medium and high-risk species that range over large areas including shelf waters, assessing distribution overlap with proposed OWF areas was identified as a priority for further research. More generally, we provide a framework to assess the impacts of OWFs on sharks and rays and identify priorities for future research.