Magazine article Science News

Acoustic Pingers Protect Porpoises

Magazine article Science News

Acoustic Pingers Protect Porpoises

Article excerpt

To the surprise and delight of conservation biologists, a new study shows that sound-emitting devices called acoustic pingers help at least some marine mammals avoid accidental entanglement in commercial fishing nets.

During 2 months in the fall of 1994, Gulf of Maine fishermen using nets equipped with acoustic pingers snared only two harbor porpoises, while those whose nets carried unactivated pingers caught 25 such animals.

This "is the first evidence that [pingers] actually work. . . . We didn't anticipate such a dramatic difference," says Scott D. Kraus of the New England Aquarium in Boston, who discussed the study at this week's Biology of Marine Mammals conference in Orlando, Fla.

Scientists estimate that only about 45,000 harbor porpoises dwell in the Gulf of Maine. That small population is threatened because each year a few thousand porpoises are killed unintentionally by the nets local fishermen use to capture cod and pollack.

"We don't believe [that depletion] is sustainable," says Andrew J. Read of Duke University's Marine Laboratory in Beaufort, N.C., another member of the acoustic pinger study.

To protect the harbor porpoises, federal officials have resorted to closing certain regions of the Gulf of Maine to commercial fishing in the last few years. As an alternative to such closures, a few researchers, with the encouragement of the local fishing industry, have explored the use of underwater alarms that send out sound waves near the low end of the porpoises' auditory range. These pingers are designed to warn the porpoises away from nets.

In the summer of 1994, however, a scientific panel reviewed available data on acoustic pingers and concluded that the few trials conducted with them had been too small or poorly designed to establish any benefit. "There was a lot of skepticism about the use of acoustic alarms," says Kraus.

Skeptics and advocates of the idea, says Read, then joined together to design what they hoped would be a definitive study of the pingers' ability to protect harbor porpoises. …

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