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.
Highlights
Gillnet bycatch is a major source of mortality in many species of seabirds, sea turtles, and marine mammals, many2018 The Authors
Trippel et al [9] found that nylon barium sulfate gillnets reduced bycatch of both porpoises and seabirds and posited that the decline in seabird interactions was a result of increased net visibility
As detailed in Ortiz et al [11], the predicted mean CPUE of the target catch of guitarfish, rays and flounders in these same illuminated sets was unchanged compared to the control nets
Summary
Gillnet bycatch is a major source of mortality in many species of seabirds, sea turtles, and marine mammals, many2018 The Authors. Zydelis et al [4], for example, estimated that seabird bycatch 2 in gillnet fisheries likely exceeds 400 000 birds annually Despite this threat, few mitigation solutions for seabird bycatch have been identified, let alone implemented on a large scale. One approach to bycatch mitigation solutions is to use sensory cues to evoke behavioural changes in animals that reduce their vulnerability to fishing gear [5,6]. Such approaches have been discussed with regard to incidental captures of sea turtles [5] and elasmobranchs [7]. Trippel et al [9] found that nylon barium sulfate gillnets reduced bycatch of both porpoises and seabirds and posited that the decline in seabird interactions was a result of increased net visibility
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