All fishermen using nets in Denmark’s Storebælt Sound will now be required to use a ‘pinger’, an underwater acoustic alarm attached to the net, to prevent endangered porpoises from getting entangled.

The new law comes into effect this summer and will apply to recreational as well as commercial fishermen.

“What we know – from the European Commission, among others – is that pingers are effective at reducing bycatch of porpoises, and they are considered the best tool for guarding porpoises against getting trapped in nets,” the food minister, Mette Gjerskov (Socialdemokraterne), told Politiken newspaper.

Unlike whales and dolphins, porpoises are the only cetaceans found in Danish waters year round. Some 55,000 porpoises live in the seas surrounding Denmark. Nevertheless, they are severely endangered.

A recent study of the porpoise population in Denmark’s inner waters – including the Storebælt Sound and the fjords – revealed that the population dropped from around 28,000 to just 11,000 in one decade.

Making matters worse, several thousand porpoises are accidentally trapped each year in fishing nets, where they end up drowning, according to the environmental research group Danmarks Miljøundersøgelser.

The government and environmental groups hope that the tally of unnecessary porpoise deaths will be drastically reduced once the new ‘pinger law’ comes into effect this summer in the Storebælt Sound.

Based on experience in the North Sea, where pingers are already required on fishing nets and lines, researchers believe that porpoises have learned to avoid areas where they hear the acoustic alarms.

“It’s fantastic that the new government has opened it up again after the previous action plan was shelved for six years under the old government,” said Greenpeace scientist and marine biologist Hanne Lyng Winter.

Winter said she was “genuinely glad” about the new rules requiring pingers in the Storebælt Sound. She added, however, that getting trapped in nets was not the only threat to porpoises in Danish waters. Over-fishing could also be starving them out, she suggested.

The government has proposed creating a study group of marine scientists, fishermen and NGOs, to study the problem and put together a broad plan to protect the porpoises and comply with the EUÂ’s nature conservation rules, Politiken reports.

Both Winter and Peter Pagh, a professor in environmental law at the University of Copenhagen, noted that despite the decision to require pingers, Denmark is still falling far short of EU rules for the protection of marine nature areas.

EU rules require that fishermen first prove that their activities will not harm the animals or plants in a protected nature area. The burden of proof lies with the fishermen.

By contrast, Fiskeridirektoratet, which overseas fishing in Danish waters, allows fishing in protected nature areas unless until someone proves that the fishing activities actually harmed the environment.