Bycatch, which is the accidental capture of non-target species such as dolphins, marine turtles, and seabirds, is a pervasive problem in the fishing industry.
Thousands of whales, dolphins, and porpoises drown from getting entangled in nets and lobster potlines every year. The problem is that these underwater creatures use echolocation to “see” and navigate around obstacles, however, most nets are “invisible” to their sonar making them really hard to avoid.
However, marine biologists in Germany have come up with an ingenious low-tech solution that can make the nets “visible” to acoustic signals so that cetaceans can dodge the nets.
Beaded nets
To make the nets visible, marine biologists are threading them with tiny beads made from acrylic glass. These beads can bounce back bio-sonar signals as echoes, which can be picked up easily by underwater sea life using echolocation to navigate the world. So far, the early trials in the Baltic Sea have suggested that the porpoises were more successful at avoiding the beaded nets than conventional ones.
Sleep swimming
That said, Marine biologist Daniel Stepputtis, from the Thünen Institute of Baltic Sea Fisheries in Rostock, identified one shortfall: some animals would still get entangled in the beaded nets, likely because they were sleeping.
Porpoises can continue swimming even while they sleep, but when they do this, they mute their echolocation. To address this issue, Stepputtis is pairing the beaded nets with an acoustic device that sounds porpoise warning signals that will hopefully warn any slumbering swimmer.
Stepputtis also plans to tune the beads to species’ specific frequencies.
Other solutions
Other solutions to the problem of bycatch have also had encouraging results. One study found that attaching green lights to fishing nets reduces the number of creatures accidentally caught up in fishing nets without impacting fish catches.
We also shared a few more solutions to this problem in the past. These include LEB, an aquatic scarecrow that protects birds from diving into nets, and AI-equipped fishing nets that help reduce bycatch.
