Anticipating the spread and ecological effects of invasive bigheaded carps (Hypophthalmichthys spp.) in North America: a review of modeling and other predictive studies

Bighead carp (Hypophthalmichthys nobilis Valenciennes 1844) and silver carp (H. molitrix Richardson 1845), collectively called bigheaded carps, have invaded the Mississippi River Basin and may have already entered the Laurentian Great Lakes where they could affect fishing and other industries. Developing models to predict potential spread and effects is difficult because local adaptation may have occurred among populations, parameter values for biological characteristics vary widely for these opportunistic generalists, and methodological differences complicate comparison and synthesis of studies. I review bigheaded carp biological parameters across a wide range of literature, including studies of native and introduced populations. I then evaluate how predictive models are parameterized, noting inconsistencies and highlighting data gaps. My analysis finds that although parameter values tend to vary substantially among and within systems, models are generally parameterized using the best information available, although bioenergetics and trophic models particularly need improvement. Some predictive tools can be updated using existing data (e.g., velocity requirements for spawning), but in other cases further research is needed. Research priorities include (1) better understanding bigheaded carp phenotypic plasticity among and within systems, (2) determining key biological traits of bigheaded carp populations at risk of seeding further invasions (e.g., Illinois River populations that may spread to Lake Michigan), and (3) monitoring bigheaded carp ecological effects on native fishes and plankton communities. A more complete awareness of strengths and limitations of predictive tools will lead to their improvement, thereby aiding managers in anticipating and counteracting bigheaded carp spread and effects.