Abstract
Abstract Data were obtained from 32 electronic tags that were glued to the fur of harbour seals (Phoca vitulina) in and around Strangford Lough, Northern Ireland, during the environmental monitoring of the SeaGen tidal turbine. This study provides the first detailed information on the behaviour of marine mammals close to a commercial‐scale tidal energy device. The turbine did not prevent transit of the animals through the channel and therefore did not result in a ‘barrier’ effect. However, the animals' behaviour did change when the turbine was operating, demonstrating the importance of allowing for behavioural responses when estimating collision risks associated with tidal turbines. Tagged animals passed the location of the device more frequently during slack water than when the current was running. In 2010 the frequency of transits by tagged seals reduced by 20% (95% CI: 10–50%) when the turbine was on, relative to when it was off. This effect was stronger when considering daylight hours only with a reduction of transit rate of 57% (95% CI: 25–64%). Seals tagged during the operational period transited approximately 250 m either side of the turbine suggesting some degree of local avoidance compared with the pre‐installation results. The results presented here have implications for monitoring and managing the potential interactions between tidal turbines and marine wildlife. Principally that the design of telemetry studies for measuring change in response to developments should seek to understand and take into account variability in seal behaviour. This study only looked at the effects of a single turbine rather than an array, and mitigation limited the ability to determine close range interactions. However, the study indicates that the effect of the turbine on Strangford Lough harbour seals was minor and that collision risk was reduced by the behaviour of the seals.
Highlights
Power generation from tidal flows is a predictable, and potentially substantial, source of renewable energy
Concerns about environmental impacts have been raised during the consenting processes for proposed tidal developments, and many of these have focused on the effects on marine mammals (Boehlert & Gill, 2010; Copping et al, 2016)
The Narrows is the only link between the lough and the sea, so animals have to pass within 500 m of the SeaGen turbine to make this journey. This restriction provides an ideal opportunity to examine the effects of an operational tidal turbine on harbour seal behaviour, and the presence of the mitigation shutdown prevents any learning about near field behavioural responses this study provides insights into whether there is any support for the concern that tidal turbines may present a barrier to transiting animals
Summary
Power generation from tidal flows is a predictable, and potentially substantial, source of renewable energy. The Narrows is the only link between the lough and the sea, so animals have to pass within 500 m of the SeaGen turbine to make this journey This restriction provides an ideal opportunity to examine the effects of an operational tidal turbine on harbour seal behaviour, and the presence of the mitigation shutdown prevents any learning about near field behavioural responses this study provides insights into whether there is any support for the concern that tidal turbines may present a barrier to transiting animals. This study uses movement data derived from three deployments of Sea Mammal Research Unit GPS Phone Tags (http://www.smru.st‐ andrews.ac.uk/Instrumentation/GPSPhoneTag/) on harbour seals in the vicinity of the Strangford Lough tidal turbine: before the installation of the turbine (2006), during the installation of the turbine (2008), and when the turbine was fully operational (2010) These data provide the first opportunity to investigate behavioural change in response to the construction and operation of an active underwater turbine. This allowed the effects of turbine operation on the behaviour of individual seals to be investigated
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