Listening in the fast lane: Detecting harbour porpoise activity in the Minas Passage
LE3 .A278 2012
Bachelor of Science
In the Bay of Fundy and elsewhere, macro-tidal coastal waters with high current speeds (>2 m/s) are sites of interest and activity for harnessing tidal energy, a renewable and predictable energy resource. However, there is currently very little understanding of the effects of tidal in-stream energy conversion (TISEC) devices (i.e. tidal turbines) on the behavior of marine mammals. The Fundy Ocean Research Center for Energy (FORCE) is testing turbines in the Minas Passage and addressing their impacts on the environment. The current research program includes examination of the presence and activity of marine mammals to address questions related to potential environmental impacts, including risk of harm to marine mammals inhabiting the area. Of specific interest is potential disturbance to the Harbour porpoise (Phocoena phocoena), the most commonly occurring marine mammal species in the Passage. This study used passive acoustic monitoring devices (C-PODs) to detect click trains (and thus activity) of these highly vocal, echolocating animals. Three units were positioned in the FORCE test area from August to November 2010 and from May to August 2011. The goal of this study was to characterize the spatial (between site) and temporal (day/night, seasonal) baseline activity of Harbour porpoises as well as porpoise activity associated with the tidal cycle and current speed. Porpoises were present on all days (May-Nov), with peak activity in late June. Significant differences were detected between sites and there was significantly greater porpoise activity (based on click trains) during the night than during the day. The C-PODs recorded significantly greater detections during ebbing tide than during flooding tide, with reduced levels of detection at current velocities >1.6 m/s. This may be a behavioral response but could also be an effect associated with detection interference at high flows (i.e. high ambient noise), effects on C-POD unit tilt at high current speed, or some combination of these and other factors.
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