Green LED lights attached to a gillnet every ten meters, apparently that’s all it takes to significantly reduce bycatch. The light keeps sharks, rays, but also squid and sea turtles from getting tangled in the net. At the same time, the catch of the desired food fish remains constant.
This is the result of a study for which a research team led by Jesse F. Senko from the University of Arizona laid out a total of 28 pairs of nets off the coast of California. One of them was equipped with the lamps, the other not. They have now published the evaluation of their catch results in the specialist magazine “Current Biology”.
According to this, the amount of bycatch fell by a total of 63 percent, that of sea turtles by 51 percent, that of the large Humboldt squid by 81 percent and that of sharks and rays by a full 95 percent. This also significantly reduced the time that the fishermen needed to haul in their nets and sort out the by-catch, which was sometimes dangerous. The boats were able to return home about an hour earlier.
The team writes that gillnets are cheap and widespread, especially among small fisheries. The nets are fixed at the desired depth with the help of floats and then left to their own devices for a while. In addition to the desired fish, many other marine life get tangled in it. Turtles or marine mammals usually drown as a result, and it often means death for sharks and rays as well. The researchers do not know exactly why a green light prevents them – but not the edible fish – from getting caught in the net. They probably recognize the lights better than other sea creatures, but that’s not enough of an explanation.