Abstract
AbstractChanges in animal movement and behaviour at fine scales (tens of metres) in immediate proximity to tidal stream turbine structures are largely unknown and have implications for risks of animal collision with turbine blades. This study used upward-facing multibeam echosounder data to detect and track animal movement comprising fish, diving seabirds, and marine mammals. Measurements over spring-neap tidal cycles at a turbine structure (no blades present) are compared to a neighbouring reference area with no structure and comparable conditions, with measurements consecutive in time to maximize comparability.The majority of tracked animals (93.4% around turbine structure and 99.1% without turbine structure) were observed swimming against the flow, with 87.5% and 97.8%, respectively, making ground and showing capability of manoeuvring in tidal stream flow speeds. Track tortuosity increased around the turbine structure compared to the reference site, particularly in the wake and at low flow speeds, indicating animal station-holding or milling behaviour. These data also evidence the benefits of multibeam echosounders to measure animal movement through larger measurement volumes rather than relying on single-beam echosounders to measure animal presence alone, including to avoid large biases overestimating the size of schools swimming against the flow measured by time-in-beam.
Highlights
Tidal stream turbines are contributing internationally to marine renewable energy generation (Smart and Noonan, 2018)
This study focuses on two consecutive deployments of the FLOWBEC platform (FoW1: 2 Jun—15 Jun 2013 comprising 12.35 days of data collection, and FoW2: 18 Jun—5 Jul 2013 comprising 17.05 days of data collection) at the European Marine Energy Centre (EMEC) Fall of Warness (FoW) tidal site in Orkney, Scotland (Figure 1) (Williamson et al, 2016)
This study has shown significant changes in animal movement and behaviour around a tidal turbine structure
Summary
Tidal stream turbines are contributing internationally to marine renewable energy generation (Smart and Noonan, 2018). Marine animals have been shown to use tidal-stream environments to increase foraging opportunities. Marine mammals (Hastie et al, 2016) and diving seabirds (Waggitt et al, 2016a) exploit high-energy hydrodynamic characteristics, which are hypothesized to increase foraging efficiency or prey availability (Benjamins et al, 2015; Williamson et al, 2019). VC International Council for the Exploration of the Sea 2021.
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