Predator recognition and anti-predator behavior in juvenile Asian carp

Predation is a determining factor influencing the strength and success of a year class in many prey fishes. Chemical, social, and similar predator cues may all inform an individual of a possible impending predatory threat. Bighead (Hypophthalmichthys nobilis) and silver carp (H. molitrix) widespread invasive fishes, and can be vulnerable to predation during their first year. Because they now overlap the niches of many native prey species, they may shoal with these species and learn about predation while doing so. Additionally, generalizing predators that have similar characteristics (e.g. odors or body morphometry) may increase the survival of an individual. The objective of this study was to evaluate how juvenile bighead and silver carp respond to threatening situations, as well as how adaptive and plastic are these responses. To achieve these objectives, I performed three separate studies that aimed to define the alarm response of these fishes, assess how group composition may influence the alarm response, and determine if the response could be generalized when exposed to taxonomically similar predators. Bighead and silver carp responded to conspecific alarm cues and both species reduced their activity, however bighead carp did so in much tighter schools than silver carp. In same-species groups of bighead carp, largemouth bass (Micropterus salmoides) odor induced similar behavioral changes, provided at least one experienced individual was present. However, when naïve bighead carp were paired with experienced golden shiners (Notemigonus crysoleucas), they matched their behavior to that of the golden shiner. Groups of silver carp conditioned to recognize largemouth bass odor only showed behavioral changes when exposed to the same predator odor, and were unable to generalize the odor of largemouth bass to recognize smallmouth (M. dolomieu) odor. These three studies indicate that there is some degree of flexibility in the response of bighead and silver carp exposed to different threatening situations, however more tests are needed to identify how the different responses may impact the relative success of these invaders as they approach novel environments