The light at the end of the funnel?: Using light-based traps for the detection and collection of a nearshore aquatic, invasive invertebrate, Hemimysis anomala

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Early detection of aquatic, non-native species can be challenging due to low densities, multiple life stages, and unpredictable conditions. This has led to calls for novel approaches to improve detection as well as facilitate control and eradication of emerging invaders. We explored if subaquatic traps that utilize the behavioral response of organisms to preferred light conditions could effectively capture Hemimysis anomala, an invertebrate that is expanding its range in aquatic systems throughout Europe and North America. Light-based traps provided a reliable alternative to monitoring with plankton nets and traps, as this invertebrate seeks refuge in crevices that are inaccessible to most sampling gear. In the field (Seneca Lake, NY USA), light-based traps of two designs—bucket and funnel traps—were highly effective at capturing Hemimysis, with limited non-target catch. Trap collections were representative of the juvenile-dominated population surveyed by concurrent net tows. In the laboratory, funnel traps were more successful than bucket traps at capturing Hemimysis. Funnel traps attracted 25 to > 80% of organisms introduced into aquaria. Once introduced into the trap, approximately 80% of organisms were retained, with no systematic difference in the demographic characteristics between organisms that remained and those that escaped. Light-based traps are a promising monitoring strategy across a range of densities (7 to nearly 1000 Hemimysis/m based on our laboratory and field studies) for this rapidly expanding Ponto-Caspian invader that has the potential to impact recipient communities. As the behavior and life cycle of many aquatic species are tied to light intensity, the traps we describe for Hemimysis may be applied to the early detection of other species for which light preferences are known. 3

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Journal of Great Lakes Research

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