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University scientists are trying to discover what kind of noise annoys a porpoise -- because the prize could be a world-beating product that is life-saving for the threatened mammal.
Members of the underwater acoustics group at Loughborough University, Leicestershire, hope to perfect an electronic "pinger" whose sounds will send porpoises swimming away from death in fishermen's nets.
Chief experimental officer David Goodson said he hopes the end product will be a small waterproof box which can be sold in large numbers to fishing fleets worldwide.
His team's efforts, involving testing the effects of a range of noises on porpoises, come as figures for deaths of the animals have raised fears among some conservationists that one important species, harbour porpoises, could disappear around much of Britain and Ireland.
Paul Jepson of the Institute of Zoology in London said the statistics were based on a survey by Cornwall Wildlife Trust, whose volunteers spent time at sea on Irish and Cornish fishing boats and counted 43 dead porpoises in nets.
Calculations from that suggested 2,300 would be found across the whole Celtic Sea, which was about 6% of the estimated area population of harbour porpoises, he said.
Death was most common in bottom-set gill nets, which form a static curtain rising from the seabed. Once trapped, porpoises were unable to reach the surface for the air they needed as mammals.
"Until now we were only guessing what the extent was," he told PA News. "Now the data suggests there is cause for real concern. It is very worrying."
Mr Goodson said Canadian attempts to scare whales from fishing nets using underwater noises had some success with porpoises too, and his team had been carrying out detailed experiments in Holland.
"We built a box of tricks which makes different types of sound, and used video to find out whether each sound attracted the porpoise or made it move away," he told PA News.
"We came up with quite a complex sound which they clearly find aversive. We don't know why, but it makes them go clear away."
The team believed it was also a world "front-runner" in developing the gadget to make it cheap and compact and able to withstand the rigours of repeated manhandling, as well as spending long periods under water.
"This is about the worst environment to put electronics into," he said. "The equipment has got to survive not only being on the sea bed but being dragged on and off boats and jumped up and down on when the nets are on deck."
Worldwide concern about threats to porpoises meant there was a large potential market, he said. Each net would require a line of "pingers".
Dr Nick Tregenza of the Cornish Wildlife Trust, was cautious about the interpretation put on his own volunteers' findings.
He believed that the reduction in fishing in the past two years meant that extinction was not a threat within 30 years, even on the worst view.
Marine biologist Mark Simmonds of the Whale and Dolphin Conservation Society said the figures were a subject for debate in which some people believed there was a risk of regional extinction.
"Anything above 1% of a population dying is regarded as setting alarm bells ringing," he added.
However, Mike Townsend, chairman of the National Federation of Fishermen's Organisations and chief executive of the Cornish Fish Producers' Organisation, condemned "emotional outbursts" by some members of the conservation lobby.
The 6% porpoise annual death figure "does not stand up to serious scrutiny", he said.
Not only had the level of fishing halved in the area since the survey, but the population figure used was conjectural.
But some Cornish fishermen had volunteered to try out the latest "pingers" from Loughborough.
"These pingers would be another cost for fishermen, but it would be a price we would be prepared to pay to be able to fish responsibly, even though we think pollution is also an important cause of death.
By Roger Williams,
PA News - 1998
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