Abstract
Flex Marine Power Ltd, in association with Islay Energy Trust, is proposing to develop a tidal energy generating project in the Sound of Islay. During consultation with NatureScot, it was advised that, as part of the marine licensing application, collision risk modelling should be carried out in order to assess the implications of potential collisions with the tidal device for:
- Harbour seal (Phoca vitulina), relating to the South-East Islay Skerries SAC [UK0030067];
- Harbour porpoise (Phocoena phocoena), relating to the Inner Hebrides and Minches SAC [UK0030393]; and,
- Grey seal (Halichoerus grypus) relating to the Treshnish Isles SAC [UK0030289].
The Encounter Rate Model (ERM) (SNH, 2016) was used to predict the number of collisions with the tidal device expected per year for harbour seal, harbour porpoise and grey seal. The density of animals at the site for each of the three species was calculated based on published data available in the public domain. Parameters associated with the size, shape and speed of the animals, the nature of the tidal channel and the specifications of the tidal device were then used to predict of animal encounters with the blades. Two scenarios were considered, one representing the 3.28 m diameter rotor that will be deployed initially, and the other representing the 5 m diameter rotor that will be deployed subsequently. The predictions are assumed to represent lethal collisions in the absence of avoidance. A 98% avoidance rate was then applied to predict the final number of collisions per year.
Number of collisions predicted for harbour porpoise, harbour seal and grey seal using the ERM model are presented in the report.