On a chilly yet sunny spring day, we set sail from the quaint coastal town of New Quay, Wales, in search of dolphins and porpoises. While I had a keen interest in spotting these aquatic mammals, Bangor University PhD student, Hanna Nuuttila, had something else in mind. She hoped to listen to their chatter underwater using C-Pods, which submerge hydrophones that collect acoustic data on the vocal behavior of dolphins and harbor porpoises. By analyzing where and when these creatures make their characteristic "clicking" sounds, Nuuttila aimed to gain insight into their behaviors in Cardigan Bay, an expansive area of water along the west coast of Wales.
We navigated the bay’s coastline to reach a 1 km square grid that Nuuttila had created months ago by tethering 44 C-Pods 200 meters apart. Each location was marked by buoys, delineating her patch of sea. Nuuttila revealed that fishermen have graciously avoided this area, agreeing to steer clear of her immersive hydrophones. The coastguard, too, has been warning seafarers twice a day to avoid this designated area. Given that each C-Pod costs about £3,000, she couldn’t afford to lose any of them, but during the recent high spring tides, some of them became completely submerged, leaving her anxious about their loss.
Cardigan Bay is a Special Area of Conservation, partly designated for its importance to bottlenose dolphins regarding their feeding, calving, and nurturing of young. Ascertaining dolphins’ whereabouts in the Bay is vital to ensure that human activities do not interfere with their survival. However, harbor porpoises also inhabit the Bay and could benefit the most from Nuuttila’s research.
Her study finds its roots in previous research where she worked on acoustic monitoring projects for the Sea watch Foundation. That study revealed that dolphins in the Bay were killing porpoises. Evidence of dolphin involvement was evident on the dentition marks seen on the porpoise’s flesh. They suffered from massive hemorrhages, and their organs seemed to be smashed. She then began conducting surveys on the interactions between dolphins and porpoises using 10-click loggers, a less sophisticated version of the C-Pod kit that she is currently using. She found that harbor porpoises regularly inhabit the area, unlike the dolphins, which only use the Bay occasionally, mostly during summers. Porpoises use the bay throughout the year, including at night when dolphins are scarce. This revelation emphasizes that the Bay is just as important for porpoises as it is for dolphins. Nuuttila feels that further research is needed to understand how environmental variables impact both species, the number of echolocating cetaceans at any time, and whether dolphins and porpoises emit more clicking sounds in groups than alone. She also hopes to determine the precise number of dolphins and porpoises inhabiting Cardigan Bay and the surrounding waters.
Nuuttila explains that they record all data and compare it with the time of clicks recorded on the nearest C-Pods. If they can demonstrate that porpoises frequent the bay in substantial numbers throughout the year, they could amend the SAC designation to provide special protection for the species.
Despite the SAC status, Cardigan Bay is a multipurpose area in which scallop dredgers are permitted in some sections. Previously, if the fishing industry argued that the dolphins left during the winter, they were allowed to dredge for scallops. However, scallop dredging is extremely destructive to the seabed and its inhabitants. If they can demonstrate porpoises use the bay as a feeding ground in both winter and summer, these activities may be restricted.
Moreover, if they can establish that there are cetacean-free regions that do not support other critical habitats, they may be available. However, the only safe approach forward is to obtain more precise information and employ the precautionary strategy until that knowledge is available. "Before allowing destructive practices, not just in the SAC, but in all marine areas," she says.
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