Shedding Light on Bycatch

We’ve reported on using LEDs on fishing nets to see if they reduced turtle bycatch in an earlier story. It turns out that there’s more. The same indefatigable team from the University of Exeter cast around to see if this applied to other bycatch and have just completed a further study using the field research originally focused on turtles to now show that fewer cormorants get drowned in nets lit with green LEDs. Like the turtle solution, this is about a reduction in numbers and not a failsafe answer to the problem, but they have demonstrated again that there are markedly fewer unintended victims when the nets are decorated with LEDs.

Compare the pair

The field research compared 114 pairs of gillnets anchored in fixed positions with one of the pair lit with green battery powered LEDs and the other unlit as a control. The team chose Sechura Bay in northern Peru as a typical site where entanglements are common. The nets are around 600 metres long and sit on the bottom of the sea and have the net mesh held up by a float line. The float line, which sits mid water, has one of the LEDs attached every 10 metres.

85% improvement

The nets were set from late afternoon until sunrise. The unlit control nets caught 39 cormorants. The illuminated nets got just 6. That’s an 85% improvement. The nets lit by LEDs also managed to snare 4 Peruvian boobies, but these were not included “due to the small sample size”.

Encouraging result

There was no drop off in the intended catch of flounder, guitarfish and rays. Coupled with the fact that LEDs are cheap, reliable and durable, this is an encouraging result that means the lights have a good chance of being adopted. The lead author, Dr Mangel, says: “It shows us that we may be able to find cost-effective ways to reduce bycatch of multiple taxa of protected species, and do so while still making it possible for fishers to earn a livelihood”.