Knowledge for better food systems

Green lights on fishing nets reduce bycatch of diving birds

Image: TonyCastro, Guanay Cormorant, Wikimedia Commons, Creative Commons Attribution-Share Alike 4.0 International

Attaching green light emitting diodes (LEDs) to gillnets (vertical fishing nets that catch fish behind the gills) reduces the number of guanay cormorants accidentally caught by 85% relative to control nets with no lights, reports a recent paper. A previous study of the same fishery has shown that illuminating nets can reduce bycatch of green turtles by 64% without reducing catch rates of the target species (the current paper did not specify catch rates of the target species). The authors hypothesise that it may be possible to tailor the wavelength of light to attract or repel specific species, according to a fishery’s needs.

Abstract

Bycatch in net fisheries is recognized as a major source of mortality for many marine species, including seabirds. Few mitigation solutions, however, have been identified. We assessed the effectiveness of illuminating fishing nets with green light emitting diodes (LEDs) to reduce the incidental capture of seabirds. Experiments were conducted in the demersal, set gillnet fishery of Constante, Peru and compared 114 pairs of control and illuminated nets. We observed captures of a total of 45 guanay cormorants (Phalacrocorax bougainvillii), with 39 caught in control nets and six caught in illuminated nets. Seabird bycatch in terms of catch-per-unit-effort was significantly (p < 0.05) higher in control nets than in illuminated nets, representing an 85.1% decline in the cormorant bycatch rate. This study, showing that net illumination reduces seabird bycatch and previous studies showing reductions in sea turtle bycatch without reducing target catch, indicates that net illumination can be an effective multi-taxa bycatch mitigation technique. This finding has broad implications for bycatch mitigation in net fisheries given LED technology's relatively low cost, the global ubiquity of net fisheries and the current paucity of bycatch mitigation solutions.

 

Reference

Mangel, J.C., Wang, J., Alfaro-Shigueto, J., Pingo, S., Jimenez, A., Carvalho, F., Swimmer, Y. and Godley, B.J., 2018. Illuminating gillnets to save seabirds and the potential for multi-taxa bycatch mitigation. Royal Society open science, 5(7), p.180254.

Read the full paper here. See also the Foodsource resource How do food systems affect fish stocks and marine habitats?

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Latin America and the Caribbean occupies the central and southern portion of the Americas. The region is home to the world’s largest river (the Amazon River), the largest rainforest (the Amazon Rainforest), and the longest mountain range (the Andes). Export-oriented agriculture constitutes an important part of the economy, especially in Brazil and Argentina. This large continent has a range of climates spanning the ice of Patagonia, the tropical forests of much of the continent, and more temperate regions in, for example, Mexico and Chile. Due to the greatly differing geography and economic development in the continent, all types of agriculture can be found in Latin America. Subsistence farming and cash cropping with coffee, cocoa and so on are common in many nations including most of central America, whereas large-scale beef production in the cerrado of Brazil provides an example of hyper-large farms run by large businesses.

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