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LED exit lights on nets help unwanted fish species evade capture

Image credit: Dreamstime

Researchers have found that attaching LEDs to fishing nets to indicate an available exit hole for non-target species could help to minimise the impact of fishing on marine environments and protect the livelihoods of people working in the industry.

According to the UN Food and Agriculture Organisation, about 35 per cent of global catches are wasted – either rotting before they hit people’s plates or being thrown back into the sea.

About a quarter of these are bycatch or discards due to the nets picking up species that are either unwanted or too small. Their capture nevertheless has a negative impact on marine ecosystems.

A team from Bangor University has trialled a system that involves attaching LED lights to larger holes in nets to act as signposts to bycatch species, indicating the direction in which to swim in order to escape.

An initial trial in the sea around the Isle of Man focused on reducing the number of haddock and flatfish caught in a queen scallop fishery.

While existing bycatch reduction devices were effective at shallower depths of 29-40m deep, in deeper and darker waters of 45-95m they had no impact at all.

Once the LEDs were added to these net 'exits' in deep water, haddock bycatch was reduced by 47 per cent and flatfish catch was reduced by 25 per cent.

The researchers believe the relatively cheap LED solution could prove very popular with fishermen due to how easily existing fishing nets can be adapted.

Under an EU regulation known as the Landings Obligation, fishermen are required to bring ashore almost everything that they catch, including fish that are not part of their quota.

If they end up catching too much of their non-target species, fishermen can see their fishery “choked” - i.e. closed for a period of months to allow vulnerable stocks to recover. It is thus in their interests to minimise the capture of unwanted fish as much as possible.

Lucy Southworth, lead author of the study, told the PA news agency: “Traditionally - and this goes back decades and maybe even centuries - fishers used lights to attract fish. Now we are turning that on its head to try and manipulate the behavioural responses in fish and other animals to either repel them away from gear or to manipulate their behaviour so they can escape from them net.

“In our case, we decided to attach the lights to the escape exit to try and guide fish towards it, so they would escape out more so than they would do if the lights weren’t there.”

Morven Robertson, senior UK projects manager at the Blue Marine Foundation, welcomed the research, saying: “We look forward to seeing how this technology can help fishermen to reduce bycatch, avoid choke species and fulfil commitments to the Landings Obligation.”

Philip Evans, oceans campaigner at Greenpeace UK, said it was “concerning” that existing bycatch reduction devices become less effective at night and in deep water.

“We hope that fishing fleets take heed of this scientific development to help them reduce their bycatch and step up their measures to eliminate it as much as possible,” he said. “But to give our oceans the best chance of recovery, we need to see catch limits set at sustainable levels, in line with scientific advice.

“We also must place at least 30 per cent of our oceans off-limits to human activity, including fishing, by 2030.”

A recent study found that while marine life around the world is currently suffering from overfishing and other human impacts, it is also very resilient and could bounce back to former levels in just 30 years if sufficient environmental measures are taken.

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