AUTHORS: Jesse R. Fischer, US Geological Survey; Josey L. Ridgway US Geological Survey
ABSTRACT: Several technologies were recently developed by the U.S. Geological Survey (USGS) to provide managers and researchers with cost-effective solutions to assess, deter, and capture invasive Silver Carp (Hypophthalmichthys molitrix) populations. These tools and techniques were designed to exploit the unique physiological and behavioral characteristics of Silver Carp. Specifically, Silver Carp exhibit strong schooling, jumping, and net-avoidance behaviors that have often created challenges for traditional methods of capture. Research on Silver Carp from a variety of habitats and population densities throughout the Mississippi River Basin has demonstrated a widespread need to create new methods to capture, deter, or control these invasive populations. Nets were developed to target low-to-intermediate densities of invasive carp by eliciting jumping while limiting bycatch. Surface-floating gill nets provide a cost-effective tool for assessing and monitoring invasive carp populations (e.g., population assessment, capturing individuals for telemetry studies). For high density populations, a corral net was designed and tested for concentrating large biomasses of fish with an emphasis on preventing escape and maintaining survival until removal. Both novel nets were designed to be used in conjunction with substrate-to-surface block-nets that can control and direct movements of individuals. Additional tools to be used with these nets include deployable underwater speakers with remote operation capabilities. These mobile acoustic deterrents were created and assessed for modifying invasive carp behavior, such as, stimulating jumping or directing movement towards areas for increased capture. Semi-autonomous watercraft were also designed and extensively field-tested to assist with invasive carp assessment and monitoring using consumer-grade sonar to estimate abundance and biomass and control strategies using remotely operated stimuli (e.g., acoustic, bubbles, lights) to concentrate fish or to elicit jumping for capture objectives. Future work will continue to demonstrate and transfer new technologies to non-USGS partners to accomplish research and management objectives across subbasins within the Mississippi River.
