Recruitment Sources and Natal Dispersal of Catfishes in the Middle Mississippi and Lower Ohio River Inferred from Otolith Chemistry

Blue and Channel Catfish are an important recreational species in the Mississippi and Ohio Rivers and are commercially harvested. However, there is a lack of data on recruitment dynamics of these species, which impedes understanding of population dynamics and predicting responses to management. The objectives of this study were to identify recruitment sources and base line emigration and immigration rates of catfishes in the Illinois section of the Ohio River and the Middle Mississippi River (between St. Louis MO and Cairo IL). Sampling for catfishes was conducted June-October 2012 - 2014 using electrofishing, trot lines, and hoop nets. Lapilli otoliths were analyzed for δ¹⁸O, Sr:Ca and Ba:Ca. Water samples from the Ohio River and its tributaries were collected from 2010-2014, and the Middle Mississippi and its tributaries from 2006-2014. These water samples were used to describe river and tributary-specific δ¹⁸O, Sr:Ca and Ba:Ca signatures. Results indicate differing patterns of recruitment between the Mississippi River and the Ohio River with little difference between species within their respective rivers. This study will be valuable for protecting important spawning and juvenile nursery habitats, and assessing interactions among catfish stocks in the Ohio River, the Middle Mississippi River and their tributaries.