Quick Dips

Sound Set to Deter Dolphins

Canterbury set net fishermen are to voluntarily use pingers on their nets to deter endangered Hectors dolphins, and are funding a $60,000 observer programme.

South East Inshore Finfish Ltd director Peter Dawson says that about 10 local fishermen, fishing in an area roughly from Kaikoura to Oamaru, are involved. His company has hired US scientist Greg Stone to analyse the results of the programme.

Studies show that pingers reduced by-catch of harbour porpoises in bottom-set gillnets in three areas (Gulf of Maine/Bay of Fundy, Washington State and Denmark) by over 75%. In the Californian driftnet fishery for swordfish, a spectacular reduction was achieved in the numbers of common dolphins caught.

"We are committed to reducing the numbers of the Hectors dolphins caught in the nets so we are pulling out all stops to make sure we are successful.

"Fishermen are often the first to initiate moves to minimise the impact on the marine ecosystem. The industry has invested heavily in research to find ways to overcome the problem and have come to the conclusion that the pingers are the way to go," Dawson says.

There are two main theories on how pingers work. One sees them as a warning device where cetaceans (such as Hectors dolphins) that spend much of their lives passively listening may respond to the sudden sound of an active pinger by "switching on" their sonar and thus detecting any gillnets in the vicinity.

Pingers may work as a simple aversive deterrent, where the cetaceans avoid the unpleasant sound, and thus the nets. Research suggests that this latter explanation is the more likely of the two.