Length-Weight Relationships for Three Asian Carp Species in the Missouri River

Bighead carp (Hypophthalmichthys nobilis), silver carp (Hypophthalmichthys molitrix), and grass carp (Ctenopharyngodon idella), collectively referred to as Asian carp, are invasive species that have been 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 are lacking. The objectives of this study were to describe the length-weight relationships (condition) of Asian carp from 2003 to 2007 in the Missouri River downstream of Gavins Point Dam, South Dakota and Nebraska to St. Louis, Missouri. All total, 388 bighead, 75 silver, and 111 grass carp were measured and weighed. Short bighead carp weighed significantly less in the upper Missouri River from Gavins Point Dam to the Platte River compared to fish of the lower Missouri River from the Grand River to the Mississippi River. Conversely, long bighead carp in the upper Missouri River attained greater weights than fish of similar length downstream. Though not significant, condition similarly varied between the upper and lower Missouri River for silver carp and grass carp.