Evaluating Current Knowledge and Future Directions of Visual Cues as Bycatch Reduction Technologies in Passive Net Fisheries

Fisheries bycatch is consistently identified as a leading cause of population decline for many species of sea turtles, seabirds, and marine mammals. Many of these species rely primarily, or in part, on visual cues to perceive their environment, and visual cues can affect behavior. Recent research suggests that utilizing visual cues on passive fishing gear, such as gillnets, can reduce incidental interactions and associated mortality. This review synthesizes studies on visual cue bycatch reduction technologies (BRTs), focusing on the use of colored nets and net illumination. It draws upon existing knowledge to discuss both potential benefits, including streamlining bycatch reduction of multiple species, and challenges, such as current cost and maintenance requirements, associated with visual cue BRT development and implementation. The success of visual cue BRTs in initial studies, primarily on gillnets, holds much promise for bycatch reduction of air-breathing megafauna in passive gear fisheries. However, this research is still in its early stages, and future studies must expand research to more passive gear types, identify and conduct local studies in applicable fisheries, consider their potential use with other stimuli as multi-sensory BRTs, and support the development of new light-emitting diode (LED) technologies that reduce cost and maintenance requirements. As a case study, I present the preliminary findings from the first year of a multi-year study on the use of green LEDs as a sea turtle BRT on pound nets in the North Carolina flounder fishery. We compared the catch per unit effort (CPUE) of experimental green LEDs and control inactive LEDs on three pound nets in Core Sound (near Harker’s Island, NC). Preliminary analyses suggest that green LEDs reduced sea turtle and elasmobranch bycatch rates but also reduced the target catch rate of flounder and other fish species. However, these results do not account for the potential influence of environmental conditions, and variables, including wind speed, reveal trends that may indicate influence on catch rates. These effects will need to be further considered after additional data collection. This research demonstrates one example of current, continued efforts to expand visual cue BRT research to multiple passive gear fisheries to increase their applicability.