Featured Image: Cape Eleuthera Institute
By: Laura Lillycrop
For sea turtles, artificial light can be deadly. Instinct drives them from their nests on beaches towards the brightest horizon, ideally the waterline on an undeveloped coast. But the bright lights of coastal development disorient turtles towards artificial light sources.
However, lights may now be the most effective means of reducing sea turtle entanglements and mortality from fishing nets. Working in Sechura Bay in northern Peru, conservation biologists at the University of Exeter have come up with a simple method to prevent sea turtles a tangled-up fate- LED lights.
The team of researchers, including the biologists from U. Exeter and NOAA, found that attaching green LED lights to the fishing nets reduces the number of sea turtle deaths by a tremendous 64 percent. The lights did not interfere with the fish catch yields.
Image Credit: Projeto Tamar Brasil
Most commercial fishing methods today involve dragging an enormous net through vast amounts of water. Inevitably, these fishing method has potential to catch and kill fish other than those species the fishermen want, called bycatch.
Rather than pollution or collisions with ship, the possibility of being caught as bycatch is the largest threat facing marine animals. Almost 1,000 marine mammals, many of which are from critically endangered species, die every day after becoming tangled in fishing equipment.
Many of these injuries and deaths take place while turtles are migrating through fishing areas. The turtles, attracted to the bait, get caught on the hooks used to catch fish.
Using 114 pairs of gillnets, the biologists attached LEDs every ten meters on one net in each pair. The other net in the pair was left lightless as the control in the experiment. The regular nets caught 125 sea turtles, while the illuminated nets caught only 2.
This is the first time light technology has been used in a working fishery to reduce the harmful effects of bycatch. Coming in at $2 for each LED, the cost of saving one turtle totaled $34. This cost could further be reduced if this technique is implemented at a larger scale.
Image Credit: University of Exeter
“This is very exciting because it is an example of something that can work in a small-scale fishery, which for a number of reasons can be very difficult to work with,” said one of the lead authors, Dr. Jeffrey Mangel, in an interview. “These lights are also one of very few options available for reducing turtle bycatch in nets.”
A variety of species, including olive ridley, hawksbill, loggerhead and leatherback sea turtles, can be found in Peru’s ocean habitats. Thousands of these threatened or endangered sea turtles die as bycatch in the gillnet fishery. Being the largest of Peru’s small-scale fisheries, it is estimated that this fishery sets 100,000 km (over 62,000 miles) in just one year.
“The turtle populations in the eastern Pacific are among the world’s most vulnerable,” said Dr. Mangel. “We are hoping that reducing bycatch, particularly in gillnets, will help with the management and eventual recovery of these populations.”
The researchers are collaborating with larger fisheries and experimenting with different colored LED lights. Their hope is to extend this effort and reduce bycatch of more critically endangered species in Peru.
We wish them the best of luck!