Gillnets Given Green Light to Reduce Bycatch

Adding lights to fishing nets can cut unwanted bycatch, without denting the desired haul, a new study has revealed... 

Bycatch, or the unintentional catching of fish and other species, is a serious problem. Not only are we removing more types of fish from the sea than we intend, but sometimes larger animals at the top of the food chain can be caught, disrupting the careful balance of nature and ultimately reducing biodiversity. But adding green lights to nets can greatly help reduce this issue.

Gillnet fishing in particular suffers from this problem. In this method, large, static nets are held like curtains under the water and fish swimming into the nets struggle to escape. It is an effective, cheap and easy fishing method, which is perhaps why it is so popular with smaller operators. However, it is prone to unintentionally catching sharks, squid, turtles and other potentially endangered marine life too.

Now, scientists have discovered that adding green LED lights to their nets can solve the problem. In a series of experiments in Mexico’s Baja California peninsula, Jesse Senko found that adding these lights cut bycatch by over 60%, but without significant decrease in actual yield of desired species.

This is likely due to the nature of the species commonly caught as bycatch, according to Charlotte Birkmanis from University of Western Australia who wasn't involved in the study. She notes that squid in particular have well developed visual systems and may be especially deterred by the lighting.

Each light trialled by the study was battery operated and moderately expensive for small fisheries. However, solar-powered alternatives are being developed that may last for years. Further, the simplicity of the change meant no additional training was necessary for the fishers.

Even so, the outlay may well already be worth it, not only to protect our marine ecosystems, but also economically. Sharks and other bycatch often tangle and rip nets requiring tedious fixing. The study found that haulback time (the amount of time required to retrieve target and discard bycatch species) dropped significantly when the nets were illuminated. It's also dangerous to remove these large animals from the nets if they are pulled aboard alive and this may result in injury to the fishers.