Biology and ecology of bigheaded carp in an invaded ecosystem

Globally, the homogenization of species has become a threat to biodiversity. As species are transported around the world, a portion of these species, released intentionally or accidentally, may become invasive and can produce negative impacts. Great effort has been invested into early identification and prevention of invasions as these are considered less expensive than managing an invasion. Unfortunately, species may exhibit varying characteristics across ecosystems, and so their behavior and potential survival in a new environment may be difficult to predict. Therefore, I examined trends in the biology and behavior of invasive fishes, including the plasticity surrounding these and how they may contribute to successful invasions, using bigheaded carps (Hypophthalmichthys spp., silver and bighead carp and their hybrids) in the Wabash River, Indiana (USA), as a case study. Trends in population characteristics appeared to vary with invasion stage. Female-skewed sex ratios, changing length-weight relationships, and earlier maturation are all characteristics that may ultimately contribute to the successful establishment of these fishes along invasion fronts. Movements could be extremely rapid but exhibited predictable patterns that may facilitate the management and control of these invasive fishes. Reproduction in these species was influenced by different environmental cues than those from their native ranges and was dependent on growing degree day rather than changes in river discharge. Hybrid bigheaded carp (silver x bighead carp) were not different from silver carp in any of the characteristics examined (i.e., movements, condition, diet) but are increasingly represented in adults and eggs in this system and may serve to increase heterozygosity. Stable isotope analysis indicated that there was little dietary overlap between bigheaded carps and native planktivores. Additionally, there was seasonal variation in resource use that may function to minimize this overlap. Overall, many of the variables examined in these studies may be influential in facilitating the successful establishment and spread of these invasive fishes