Methods for tracking fine scale underwater movements of marine mammals around marine tidal devices

2 Introduction

The Scottish Government has a target for 100% of Scottish demand for electricity to be met from renewables by 2020 creating a balanced portfolio of both onshore and offshore technologies. Offshore renewables have the potential to make a significant contribution to Scottish Government targets for delivery of renewable energy generation. The Scottish Government has the duty to ensure that the development of offshore renewable sectors is achieved in a sustainable manner in the seas around Scotland.

Strategic Environmental Assessments ( SEA) on offshore renewable development has identified a need to evaluate potential interactions between offshore renewables and marine wildlife as a matter of priority so that appropriate mitigation can be investigated and applied. One concern with respect to the impact of tidal turbines on marine mammals is the potential for mortality or injury through collision with rotating turbines and the ability for marine mammals to take avoiding action (Wilson et al. 2007a). To evaluate the risk of such collisions means understanding the fine scale underwater movement of these mammals within the immediate vicinity of tidal turbines.

Existing technologies for tracking underwater movements are diverse and include satellite/ GPS telemetry, passive acoustic monitoring, active sonar and video techniques. Telemetry devices have long been deployed on seals to answer a range of research questions, including how seals use the marine environment, foraging patterns, diving behaviour and temporal/spatial distribution. They have the potential to provide good spatial coverage but are restricted in terms of tracking fine scale underwater movements and, their reliance on being able to predict the movement patterns of individual animals which may rarely enter the areas of interest. Active and passive sonar have been actively employed in areas of tidal development ( e.g., Ramsay Sound, European Marine Energy Centre ( EMEC), Strangford Lough), and when placed within the vicinity of the tidal devices may offer a more appropriate method for direct observations of potential collisions. Video can provide data on movements but may be restricted by limitations on underwater visibility due to local conditions ( e.g., turbidity, light constraints, biofouling).

The aim of this project is to review current and developing technologies for tracking the fine scale underwater movements of marine mammals in high energy tidal sites, and to predict the feasibility of these technologies for direct observation of potential collisions. Possible development of new technologies should also be investigated where current devices may not be applicable.

2.1 Objectives

In response to this gap in knowledge, we have been tasked by Scottish Government to

a. review all current and near-future technology for tracking the fine scale underwater movement of marine mammals in the vicinity of a turbine

b. predict the feasibility of these technologies for direct observation of movements and possible collision in high energy tidal stream environments

Our precise remit is provided in Appendix I. The technologies we describe here are continuously being developed and so this document will be reviewed on an annual basis.

In Appendix II we provide, as a case study, a scenario to provide fine scale interaction data at the proposed Sound of Islay turbine array development. The information provided in the case study reflects the position at the time of this reports preparation.