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Dolphins, porpoises and whales will be able to avoid getting snared and
drowned in a new type of fishing net developed by Atlantic Gillnet of
Gloucester, Massachusetts (WO 00/57696). Cetaceans get trapped in standard nets
because their echolocation systems fail to detect the net’s thin nylon
filaments. In the new net, barium sulphate is added to the nylon so that it
reflects sound in the 120 to 140-kilohertz range used by the mammals for
echolocation. The net can then be “seen” by cetaceans—though not by fish.
The company says that in tests using several kilometres of nets, normal nylon
nets caught at least five cetaceans, while the modified nets trapped none.