SMRU Consulting has been monitoring marine mammals around marine renewable energy projects since 2006. Our experience includes the SeaGen device in Northern Ireland at (the world’s first grid connected tidal turbine), the DeltaStream device in Wales, the MeyGen array in northern Scotland (the world’s largest planned tidal turbine project), and since 2009, in the upper Bay of Fundy, where world record tidal ranges occur and Canada’s first grid connected turbine was deployed in 2016.
We use a variety of methods to understand marine mammal-turbine interactions (such as collision risk and acoustic disturbance), from animal tagging, and land-based observations to sonar and passive acoustic monitoring (PAM). One long-term PAM study focused on Bay of Fundy harbor porpoise has just been published in the Journal of Ocean Technology. Using C-POD click train detectors, SMRU Consulting North America, working with colleagues at SMRU Consulting Europe, Acadia University and Fundy Ocean Research Center for Energy (FORCE), collected multi-year data on harbour porpoise echolocation activity before installation, during installation and during operation of an OpenHydro 2 MW turbine at the FORCE demonstration area in Minas Passage, Nova Scotia (see map below).
Overall, porpoises were detected on 99% of days across 1,210 study days, at a median of seven minutes per day. Statistical models (GAM-GEE) predicted that click detection rates varied significantly by time of year (peaks in mid-June and early November), by tidal current speed and tidal height (preference for 0-2.5 m/s ebb tides), by time of day (higher click activity at night), and across the lunar cycle (see figure below). The PAM surveys were affected by sediment transfer noise during high tidal speeds which led to the C-POD memory maxing out and therefore lost monitoring time (see % Time Lost in figure below). This baseline data helped us to understand the baseline porpoise activity, as well as the limitations of the monitoring methodology.
A second statistical model was then developed to take these environmental factors into account during five months of turbine operations. This new analysis highlighted that there was no evidence of porpoise exclusion in the mid-field range (200 – 1,700m) during turbine deployment and operations (presence detected on 98.5% of days), but click activity was significantly reduced at the C-PODs closest to the turbine (200 – 230 m) and increased at the site 1,700m away, suggesting short range acoustic effects on activity and spatial use by porpoises. This study highlights the value of using PAM to monitor dynamic tidal sites across long time periods and importantly develops new methodologies for robust turbine noise environmental effects studies. These studies (combined with new drifter and on-turbine near-field monitoring) continue as new turbines are deployed at the FORCE site.
A full version of the paper by Tollit, Joy, Wood, Redden, Booth, Boucher, Porskamp, and Oldreive is found here.
GAM-GEE smoothing functions (red) overlaid over the domain of a set of environmental variables. The y-axis denotes the probability of detecting at least one porpoise in a 10-minute window, i.e., P(BinDPM=1), and how this varies over the range of environmental variables on the x-axis.