Effective rapid-response protocols and early detection techniques are critical to preventing the spread of non-native species in the early periods of colonization. However, low abundance and restricted spatial distribution during the initial stages of establishment and range expansion make detection difficult. These challenges lead to most invasive species being detected well after they have become established, when control options are limited, and ecological and economic damages are widespread. We explored a novel early detection approach with subaquatic traps that utilize the behavioral response of organisms to preferred light conditions to determine if light-based traps could effectively capture non-native Hemimysis anomala (hereafter Hemimysis). Although all Hemimysis avoid day-time light, they are attracted to dim light (< 10-1 lx). Hemimysis are expanding their range throughout Western Europe and the Laurentian Great Lakes (North America) region. Collection of Hemimysis is challenging compared to most other plankton for several reasons, including its use of interstitial spaces in the benthic zone during the day and that disturbances from sampling can induce escape behavior in Hemimysis.
Results/Conclusions
Light-based traps were highly effective at attracting and retaining Hemimysis, which suggests that light-based traps could be an effective early detection and potential control strategy for Hemimysis and aquatic invasive species with known light preferences. To our knowledge, our study is the first to suggest the use of light-based traps for the targeted detection of aquatic invasive species. For Hemimysis, light-based traps provide a reliable alternative, and improvement, to monitoring with plankton nets. In the field (Seneca Lake, NY USA), light-based traps of two designs—bucket and funnel traps—captured Hemimysis, with limited non-target catch. Lighted bucket and funnel traps captured more Hemimysis than traps without light (Kruskal-Wallis, H3, 18 = 9.0, p = 0.03), but catches from several three-hour periods during twilight/night did not differ (p > 0.05). Trap collections were representative of the juvenile-dominated population surveyed by net tows. In the laboratory with known densities of Hemimysis, funnel traps were more successful than bucket traps at capturing Hemimysis (Repeated G-test = 104, p < 0.001). Once introduced into the trap, approximately 80% of organisms were retained, with no systematic difference in the demography between organisms that remained and those that escaped. 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.