A simple and inexpensive change in the equipment used by Namibian fishing boats saves tens of thousands of vulnerable seabirds each year, the researchers estimated.

Some industrial fleets often use long lines equipped with thousands of baited hooks, which attract seabirds. When trying to pull the bait, birds can get tangled in the lines and die.

But by installing pieces of red or yellow garden hose, each a few feet long, to separate the lines towed behind the boats, they were successful in scaring the birds and avoiding a considerable number of deaths, according to a study by the journal Biological Conservation.

It is estimated that more than 22,000 birds were accidentally killed by longline gear in 2009. But only 215 are believed to have died in 2018, despite boats using more hooks that year.

Among the many species that have benefited are white-chinned petrels, Atlantic yellow-nosed albatrosses and northern gannets, all of which have declining populations.

“In many other areas where I work and where we are losing endangered species, it would be unheard of to reduce mortality by 90% over a decade,” said co-author Steffen Oppel of the RSPB Center for Conservation Science in Cambridge. He and his team used data from surveys aboard Namibian ships to assess the total number of seabird deaths each year.

The waters off the coast of Namibia are rich in nutrients and are home to abundant marine life. For seabirds, it is a crucial feeding ground.

But, in the past, boats sometimes picked up crates full of dead birds that had caught on to fishing lines.

“The fact that we’ve done something about it… it gives me a great sense of joy and accomplishment,” said report co-author Titus Shaanika of BirdLife International’s Albatross Working Group in Namibia.

The use of bird scaring devices on fishing lines became mandatory in Namibia in 2015.

Shaanika, who is employed by the Namibia Nature Foundation, added that local industry is generally supportive of methods to reduce bird mortality, in part because of their relatively low cost. It costs around N $ 4000, or £ 200, to install watering streamers on a long fishing line.

Along with the colorful garden hose, which is prepared by a team of five women working in Walvis Bay harbor, environmentalists have also encouraged the use of weights attached to the baited hooks. These sink hooks up to 10 meters or more below the surface – too deep for seabirds to reach when diving.

“I think it’s a real achievement,” said Professor Ed Melvin of the University of Washington, who was not involved in the research but who designed bird scaring line systems.

Experiences dating back decades show the effectiveness of such methods, he added, but it is rare to find a case study proving that they work on such a scale.

Because albatrosses don’t begin to breed until later in life – and even then only sparingly – their populations are particularly susceptible to adult death, Melvin said. This is why the efforts to protect them are so important.

Namibian trawlers – who drag nets through the water to catch fish – have also switched to using streamers on their gear. The study found that the number of birds killed had decreased although the reduction was not as dramatic as for vessels using long baited lines.

The study authors suggest that this is likely because some crews are reluctant to use bird scaring lines in case they get tangled in their fishing gear.

Shaanika said her group was now working with trawlers to install equipment that would reduce the risk of this happening. “It shows how much we can accomplish if we work together and listen to each other,” he said.