Seabird use of tidal stream environments and potential interactions with tidal energy devices

Abstract

**Abstract:** Marine renewables, including tidal energy devices, are increasingly being deployed across the world to mitigate climate change. However, there are concerns that marine wildlife will experience negative interactions with such devices, for instance through collisions or displacement. The UK holds ca. 50% of Europe's tidal energy resource and contains numerous tidal development sites yet is also home to internationally important seabird populations. In the face of over-fishing and climate change, additional pressure from stressors such as tidal turbines could be devastating. Therefore, to ensure sustainable deployment of tidal energy devices, there is a need to quantify any adverse effects on seabirds. Before effects can be assessed, suitable methods to do so need to be identified. We therefore developed a conceptual framework to aid in the choice of survey method(s) to gather data on seabird behaviour relevant to interactions with tidal energy devices. Following a literature review of available methods in the context of this framework we identified, amongst others, an opportunity for enhanced use of bird-borne biologging and telemetry (bio-tracking) data, as well as the need for research into close-range overlap and behaviour around turbines and the environmental variables underlying seabird use of tidal stream environments. Subsequently, we developed an analysis workflow for the use of bird-borne bio-tracking data in assessing spatial overlap with marine renewables and applied it to European shags (Phalacrocorax aristotelis) and tidal turbines in the Pentland Firth, Scotland. We found that at the current scale of tidal site leasing in the UK overlap was minimal (0.14%), however at the scale of future/planned development areas, overlap was very high (99.4%). Research into the importance of tidal velocity and bathymetry to use of tidal stream environments by diving seabirds will further clarify potential effects from tidal energy devices. **Authors:** Natalie Isaksson¹, Benjamin Williamson¹, Jonathan Houghton², Jared Wilson³, Elizabeth Masden¹ ¹University of the Highlands and Islands, ²Queen's University Belfast, ³Marine Scotland Science