Increase in bycatch rates of plunge- and surface-feeding seabirds observed while setting and hauling bottom set gillnets equipped with LED lights

Seabird bycatch in gillnets is a worldwide problem with few if any available mitigation tools. LED lights attached to the gillnets have been suggested as a potential solution, and a study in Peru showed promising results where bycatch of diving seabirds was reduced by adding LED lights to bottom set gillnets. In this study the potential bycatch reduction of LED lights was tested in a set gillnet fishery that targets Atlantic cod Gadus morhua in Iceland. A variety of seabirds such as common guillemots, cormorants, eiders, northern gannets, northern fulmars, and gulls have been observed as bycatch in that fishery. In a paired trial, nets with and without LEDs were fished off a commercial gillnetter in western Iceland. The LED-equipped net sets caught significantly more seabirds while a slight but statistically insignificant reduction in fish catches was also observed. The seabirds caught in the LED-equipped nets were mainly northern gannets and northern fulmars, plunge- and surface-feeding birds, which seemed to be attracted to the lights while hauling and setting the nets. Caution should be taken when implementing the use of LED lights on gillnets or trawls as while they might reduce bycatch of some taxa of diving seabirds or sea turtles, it is possible that some bird species or groups of bird species are attracted to the lights, in particular during hauling and setting of the nets.