Patterns in spatial use and movement of Silver Carp among tributaries and main-stem rivers: Insight from otolith microchemistry analysis

Abstract Invasive Silver Carp (Hpophthalmichthys molitrix) have established populations throughout the Missouri River basin, including in the Kansas River. Understanding the spatial extent under which these invasive fish function in large, open river systems is crucial to inform management efforts. The Kansas River may play a vital role in the life-cycle of Silver Carp in the Missouri River basin as the main-stem Missouri River has undergone a multitude of alterations, creating a channel with greater mean depths and velocities. Here, we used otolith microchemistry of Silver Carp from the Kansas River to reconstruct environmental histories as a means to assess the proportions of resident and transient individuals. Silver Carp within the Kansas River were predominantly residents (adults = 54%; juveniles = 65%) with the majority of reproduction coming from within the Kansas River itself. These results suggest removal efforts in the Kansas River may be effective means of managing this invasive fish species. Transient individuals exhibited short durations of signatures indicative of the Missouri River (mean percent of data points for adults = 10% and juveniles = 36%), suggesting movements into the Missouri River were brief. These results highlight the importance of connectivity of tributary habitat among large rivers and provides important information for invasive species management.