How plastic bottles could save dolphins from fishing nets

How plastic bottles could save dolphins from fishing nets describes research aimed at reducing bycatch, which the article calls the world’s largest killer of dolphins, porpoises, and whales. It explains that gillnets are thin nylon, nearly invisible and nearly silent, so echolocating animals may detect them too late to avoid entanglement. For years, battery-powered pingers have helped in some areas but are costly for small-scale fishers. The approach described comes from Per Berggren of Newcastle University, who proposed bolting empty plastic drink bottles onto nets to make them easier to hear. A bottle traps pocket air and also includes a metal bolt that clinks as waves move the net, mimicking a pinger signal. Lab tests suggested one bottle could make a net 100 to 1,000 times easier to detect. Field trials across three fisheries totaled more than 1,600 net deployments; results were most promising off southern Brazil, where seabed nets with bottles recorded no dolphin catches while control nets did. Off Zanzibar and Peru, outcomes were less favorable.