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Plastic beaded fishing nets could prevent dolphin bycatch

Threading tiny plastic beads onto fishing nets has potential to prevent thousands of small whales, dolphins, and porpoises from drowning each year.

It’s rare to hear that adding plastic to our oceans could actually solve environmental issues, but when 300,000 cetaceans die after getting stuck in fishing nets each year, ocean scientists have become desperate for a solution.

Brainstorming began with acknowledging the echolocation that dolphins and other small whales use to navigate oceans and find their prey. The animals’ clicks and whistles are capable of travelling an impressive 2km underwater and are vital for the animals to sense obstacles that might be ahead.

But the various kinds of mesh used to fashion fishing gear can be thin and hard to detect using echolocation as they aren’t thick enough for sounds to bounce off them. With no warning signal, the animals continue ahead and end up swimming into a trap.

Using tiny spheres made of acrylic glass, marine biologists in Germany have developed a new concept that will make it easier for dolphins to detect nets and hopefully avoid encountering them altogether.

Once attached to nets, the tiny acrylic beads – made from a kind of polymer – are hard and dense enough for dolphin and whale sounds to bounce off them, indicating to pods that something is in their path.

This echoed warning is believed to be enough to caution cetaceans from continuing ahead at high speeds. To fisheries delights, the beads have the same density as water and add very little weight to fishing gear.

In the first trials of the newly bedazzled nets, things looked optimistic. Just off the Danish island of Funen, harbour porpoises completely avoided contact with nets when their echolocation sounds bounced off the acrylic beads.

During the trial, researchers recorded the animals’ acoustic signals, hoping to gather more understanding of their behavioural responses to the beads. This new information gathering could help with future designs.

However, in secondary trials conducted in the Black Sea, it became clear that the beaded nets still faced some limitations. In ten trial fishing rounds, five porpoises swam into standard nets and two were caught in the beaded ones.

At present, it’s unclear why the porpoises didn’t completely avoid the modified nets. The researchers suspect that the captured dolphins could have been asleep, as the animals tend to continue swimming ahead slowly – even while resting.

In this case, the use of artificial dolphin warning sounds could be useful in deterring cetaceans from swimming near fishing gear. Devices producing these sounds are already used where the ocean mammals circulate in waters dominated by bustling fishing industries.

A company called Fishtek developed the devices after 8 years of research into the acoustics of dolphins and porpoises. Their goal is to offer a low cost, durable, and practical solution to rising numbers of ocean mammal bycatch each year.

The health and overall richness of life in the ocean has been highlighted as vital for sustaining life on land.

In line with that widespread realisation, let’s hope that beaded nets and other deterrent devices become the norm – or even enforced by fishing regulations – to protect marine environments now and in the future.

 

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