Demographics and Interstate Management Implications for Flathead Catfish in the Lower Wabash River, Illinois and Indiana

Flathead Catfish Pylodictis olivaris in the lower Wabash River, Illinois and Indiana, are currently exploited by anglers and commercial fishers under the same fishing regulation; however, the regulations differed between the states prior to 2015. We assessed demographics of Flathead Catfish in this interstate river to gain baseline information to create models to test for sustainable exploitation rates under the new regulation and several hypothetical scenarios. During 2010-2012, we sampled 951 Flathead Catfish (length = 343 +/- 5.6 mm [mean +/- SE], weight = 914.5 +/- 55.6 g, age = 3.5 +/- 0.07 years) using pulsed-DC electrofishing, AC electrofishing, commercial harvest, and hoop nets. Mean relative weight of Flathead Catfish was greater than 100%, and proportional size distribution indices (electrofishing = 35, hoop netting = 54) suggested a quality fishery. Total annual mortality (electrofishing = 0.48, hoop netting = 0.54) was similar to estimates in other Midwestern rivers. Yield-per-recruit models predicted that growth overfishing may occur over time under the current regulation; however, demographic metrics relate to recreational and commercial creel assessments. Our results suggest that the current minimum length limit could be raised to increase yield and reduce exploitation. Our findings also demonstrate several useful field and modeling techniques to assess catfish (family Ictaluridae) populations in environments that are difficult to sample and that lack fishery-independent information.