Guidance to inform marine mammal site characterisation requirements at wave and tidal stream energy sites in Wales

There is a growing consensus amongst regulators, statutory nature conservation advisors and developers and their environmental consultants that a ‘one size fits all’ approach to marine mammal site characterisation survey to inform consenting processes for wave and tidal stream projects is not fit for purpose. Furthermore, it is generally recognised that they may not always provide useful information for underpinning environmental assessments. There is a need to tailor pre-application surveys to a) provide specific information in relation to the particular types of impacts posed by the project, and b) to the likely degree of risk of significant impacts to marine mammals posed by the project. This report provides a mechanism for assessing b) and provides guidance on a) how to tailor survey effort to better provide information to inform specific impact assessment predictions. Section 2 of the report provides an introduction and section 3 provides a summary of the legislative background to the requirement for pre-application data gathering. Section 4 provides an overview of the information requirements for wave and tidal stream energy projects across a number of identified main impact pathways. A number of general requirements for informing all potential impacts of projects were identified, such as a basic understanding of which species are present at a site and an understanding of the functional use of a site. A number of specific impact pathways were identified for wave and tidal energy projects, such as collision (mainly tidal) and disturbance (wave and tidal). For each impact pathway a set of individual information requirements were identified. For collision impacts the key information requirements were those which would enable a robust, quantitative prediction of collision rates. Specifically these are metrics which will help to predict the potential rate of encounter between marine mammals and the moving parts of devices such as information on animal flux through the project area and how this varies over time. It is accepted that there are important pieces of information that have a large bearing on the prediction of the magnitude and consequence of collision impacts, such as evasion and avoidance, which cannot be informed by pre-application surveys and the uncertainty in collision predictions as a result should be borne in mind. For disturbance related impacts the important metrics are likely to be a measure of the density of animals at the site to allow an estimate of the number of animals likely to be affected and an understanding of why animals are present at a site, to allow a prediction of the nature and consequences of any disturbance. Disturbance can result in displacement of animals away from areas but it can also result in disruption to behaviours which may result in a reduction in breeding success or survival without any displacement. A number of other impact pathways were also explored although it is noted that these impacts are unlikely to drive survey requirements in isolation from those considered above. The third impact pathway considered was indirect impacts mediated through a change in prey availability. The information requirements are similar to the impact of disturbance; how many animals are using the site and their behaviour and whether they are feeding (and what they are feeding on) in particular.