Population size of pallid sturgeon, Scaphirhynchus albus (Forbes & Richardson, 1905), in the lower Missouri River near Kansas City, Missouri, USA

Summary The objectives of this study were to investigate the population size of hatchery-reared and wild pallid sturgeon, Scaphirhynchus albus (Forbes & Richardson, 1905), in a 43.3 river kilometer (rkm) reach of the Missouri River downstream of Kansas City, Missouri, USA and compare these with previous published estimates. This reach has been shown to represent the abundance and distribution of the pallid sturgeon population throughout the lower Missouri River, and was therefore chosen for this study in order to monitor progress towards recovering this federally endangered species. The robust-design approach was used within the Program MARK using mark-recapture data of fish sampled from 2011 to 2013. The annual population estimates of pallid sturgeon varied from 6.1 to 11.1 fish/rkm, of which known hatchery-origin pallid sturgeon (5.5 to 10.2 fish/rkm) were much more abundant than those of wild origin (0.6 to 0.9 fish/rkm). These population estimates are drastically fewer than those published for another reach of the lower Missouri River and represent far less advancement (12–18%) towards meeting the five wild adult fish/rkm criteria for considering reclassification of pallid sturgeon.