Bighead carp Hypophthalmichthys nobilis, silver carp H. molitrix, black carp Mylopharyngodon piceus, and grass carp Ctenopharyngodon idella, collectively referred to as Asian carps, are invasive species that were either accidentally or intentionally introduced into the Mississippi River basin. The expansion of Asian carp into the Missouri River is not well understood and knowledge of population characteristics within this river were lacking. The objectives of this study were to describe the relative abundance, size structure, and spatial and temporal trends of Asian carp using multiple gears from three long-term fish community monitoring programs in the Missouri River downstream of Gavins Point Dam, South Dakota and Nebraska from 2003 to 2007. A total of 1,307 bighead, 1,280 silver, 624 grass, and 0 black carp were captured. The majority of adult bighead carp were captured in overnight hoop nets (38%) and adult silver (14%) and grass carp (23%) were most commonly caught in overnight experimental gill nets. Mini-fyke nets captured almost exclusively, young of the year Asian carp (≤ 80 mm), while gill, trammel, and hoop nets collected a wide length range of fish (81 – 1,200 mm). The relative abundance of all three Asian carp species did not significantly differ among years; however, spatial trends were found as relative abundance was highest in the Missouri River downstream of the Platte River. Short Asian carp weighed less in the Gavins Point reach compared to downstream of the Grand River in Missouri. Conversely, long Asian carp in the Gavins Point reach attained greater weights than fish of similar length downstream. We found that multiple sampling gears are necessary to monitor Asian carp population characteristics in the Missouri River. Asian carp populations appear to be well established in the Missouri River and it is increasingly important to understand the affects these invasive species have on the native fish community
