Predator effects on the survival of juvenile invasive carp in simulated backwater habitats

Numerous control methods are in use and under development to manage invasive carps in the United States. Commercial harvest, electric deterrents, and chemical toxicants, among other methods, are most efficient at targeting larger individuals. Research on methods to control recruitment of juvenile invasive carps has been limited. Our primary objective was to assess the vulnerability of juvenile invasive carp and common native forage species, gizzard shad (Dorosoma cepedianum) to native fish predators. Eighteen two-week long experiments, from April–October in 2015 and 2016, were conducted in experimental ponds with differing habitats (structure, vegetation, or open), simulating backwater habitats that are commonly used by juvenile invasive carps. Bowfin (Amia calva), channel catfish (Icatalurus punctatus), shortnose gar (Lepisosteus platostomus), hybrid striped bass (Morone saxatilis × Morone chrysops), largemouth bass (Micropterus salmoides), blue catfish (Ictalurus furcatus), flathead catfish (Pylodictis olivaris), walleye (Sander vitreus), northern pike (Esox lucius), and smallmouth bass (Micropterus dolomieu) were tested as predators of bighead carp (Hypophthalmichthys nobilis), silver carp (Hypophthalmichthys molitrix), grass carp (Ctenopharyngodon idella), and gizzard shad. We observed prey survival rates across seasons, habitats, and predator species. Invasive carp odds of survival varied from those of native gizzard shad between years. Hybrid striped bass, largemouth bass, smallmouth bass, and northern pike were effective predators of all tested prey species. Largemouth bass and smallmouth bass consumed bighead carp and silver carp over gizzard shad and grass carp (log OR < 0.5). Our results demonstrate the importance of habitat and cover availability, and that predator management may be a potential control method for juvenile invasive carps. Future research may consider effective predator densities, as well as studies in natural habitats.