Here’s a cool new paper by scientists at the Scottish Association for Marine Science on how porpoise use tidal stream habitats.

Passive acoustic monitoring has been used to study harbour porpoise in the Great Race of the Gulf of Corryvreckan (Scottish west coast), where the tide races through the narrow strait at speeds >4m/s to create one of the worlds largest permanent whirlpools. C-PODs were deployed using two methods: static moorings and drifters.

Their results showed that C-PODs moored in the path of the Great Race recorded a significant increase in detections during the energetic tidal jet. Despite the extreme tidal flow speeds and the turbulence all the drifting recorders survived and detected porpoise during different tidal phases. The data showed a strong relationship between detections and flow speeds, with porpoise detections correlated with fast currents. Most of the clicks recorded by the drifting C-PODs were detected in the Great Race or in surrounding eddies during westward floods. The drifting C-PODs recorded long encounters within the Great Race and out at the Firth of Lorne with encounters lasting >60 min. These data suggest that porpoises moved downstream with the flow. Check out the Figure below:


[/media-credit] Harbour porpoise detections (PPM: porpoise-positive minute).

The authors concluded that porpoises spend most of their time in relatively low-energy environments, but that they congregate at the western entrance to the Gulf of Corryvreckan as the flood tide starts and move downstream with the flows.

Check out some of our PROJECTS using C-PODs:

Our REPORTS and papers involving PAM and C-POD analysis include: