Overfishing is wreaking havoc on the oceans, and the problem is as much about what we catch by accident – by-catch – as it is about the fish we are attempting to get. This is especially problematic for huge, long-lived animals such as sharks and sea turtles, whose numbers are slow to recover. Attaching lights that dissuade non-target species while having no effect on the fish we want to catch could be the answer or at least a significant part of it. Finding a means to keep undesired animals out of fishing nets is a good idea, but it comes with a drawback.
When the critters we do not want include mammals, reptiles, sharks, and invertebrate cephalopods, it is difficult to think of a single solution that would work for all of them without diminishing target fish captures. Nonetheless, experts such as John Wang of the National Oceanic and Atmospheric Administration (NOAA) report in Current Biology that this is exactly what they saw in the form of green LEDs sprinkled along the float lines of nets. Even better, the fishing crew may benefit from the notion, thus it may not need to mandate by law.
Small-scale fisheries provide food and jobs for a huge section of the world’s population. The gillnets they utilize, on the other hand, are deadly to marine life that is too huge to fit through their nets, including numerous creatures of little or no use to the crew. The elimination of apex predators from these ecosystems by accident can have disastrous consequences for other species. Green LEDs are placed every 10 meters (33 feet) along the edge of 28 nets set to collect grouper and halibut off the coast of Baja California, with the remaining nets serving as controls. By weight, the lit nets netted 63 percent fewer by-catch, including 81 percent fewer squid and 95 percent fewer sharks and rays.
Ironically, preserving turtles was almost the least effective portion of the project, despite the fact that it was motivated by their good location in the green section of the spectrum. Nonetheless, a 51 percent reduction in deaths for the world’s most endangered vertebrate group is nothing to sneeze at, and turtles fared better than undesirable finfish, which had a 48 percent drop in deaths. Meanwhile, the amount of commercially valuable fish caught by the nets was the same. More halibut, a specific aim, caught in the lit nets; however, this could have been by accident.
The cost of attaching and powering the lights is evident — $140 per net – but the researchers are looking into less expensive solar-powered choices and spacing them further apart. Furthermore, untangling by-catch from nets takes a lot of time, reduced by 57 percent with the lit nets. Operators of fishing boats may approve the plan if they believe the time saved is worth the money.
“It’s critical for anglers to understand that there are actual rewards available to them.” This is important for the fishing industry’s adoption of such technologies,” Wang said in a statement. Previous research on the lighting for protecting turtles has yielded positive results. These have resulted in some adoption of the approach, though not on the scale necessary. Other potential beneficiaries, such as dolphins, have been investigated in a few articles. The evaluation of total by-catch across all species, as well as the measurement of time saved in untangling, are both novel aspects of this study.
