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Pingers Protect Hector's Dolphins

Unusual electronic devices floating in Akaroa Harbour have been scaring away Hector's dolphins, but all in the name of preserving the marine mammals. The acoustic "pingers" were put in place as part of research conducted by Dr Jennifer Brown of Canterbury University and her students.

Hector's dolphins are one of the world's rarest marine mammals and are found only in New Zealand's waters. The small dolphins are often seen close inshore which makes them vulnerable to getting tangled in set nets.

Electronic technology is being applied to the problem of accidental entanglements. Acoustic "pingers" which emit a sound to warn dolphins away from nets have been successfully trialled overseas and it seemed likely the same technology could be used here.

Field work for the research project was conducted within Akaroa Harbour. Acoustic pingers were attached with fishing line to buoys set the same distance apart as the two ends of a set net. The pingers emit a sound for 300 milliseconds, every four seconds.

The research team used observations from theodolites stationed on cliff tops to track dolphin movement around the sound source. If the pingers were successful you would expect the dolphins to shy away from the sound source.

Preliminary results from the project are encouraging. In 1996 the observed dolphins responded to the active pingers in the study area by staying further away from the sound source.

For Brown the project is part of her ongoing interest in the conservation of the species. Ecological research is challenging. Natural populations are highly variable, and often with ecological data text-book analysis methods are not feasible. Brown and her team, are looking at questions like how much data is needed to be confident that the pingers are successful. This question involves assessment of risks, the risk in making the wrong decision, and the risk in not acting soon enough.

The research project is a good example of the application of technology to biology. It is an important project for marine mammal conservation.

If the acoustic pingers prove to be successful this will be very encouraging for conservation work aimed at reducing the risk of set net entanglement of a very rare marine mammal.