Population Demographics of Bigheaded Carp and Multiple Commercial Bycatch Species in Pools 16-19 of the Mississippi River

Silver carp and bighead carp (bigheaded carp) have spread throughout the Mississippi River basin since their introduction in the 1970’s. Highly adaptable life history traits have contributed to their invasiveness and their ability to negatively affect native fish populations and ecosystems. Bigheaded carp can drive density dependent reductions in their body condition and that of other native species. Detection of a deviation from body condition baselines in bigheaded carp and native species over time can be used as a surrogate to evaluate tools used to reduce bigheaded carp populations. Therefore, the objectives of our study are to track body condition of bigheaded carp and multiple commercial bycatch species over time in pools 16-19 in the Upper Mississippi River. Gill nets were deployed to capture silver carp, bighead carp, and associated bycatch during the 2015- 2019 field seasons. Length and weight were recorded from all fishes and relative weight determined using standard weight equations for each species. Bigheaded carp body condition has remained steady indicating densities are remaining low. Trends in body condition and population demographic data can be used to evaluate the effectiveness of harvest, help managers populate spatially explicit models and prompt increased strategic removal efforts.