Demographics of a Commercially Exploited Population of Flathead Catfish (Pylodictis olivaris) in the Wabash River

Flathead catfish, Pylodictis olivaris, are a popular game and commercial fish in the Midwestern United States. In the lower 322 km of the Wabash River, flathead catfish are commercially and recreationally harvested by Illinois and Indiana fishers. Current management regulations are different between the two states; Illinois and Indiana have minimum length limits of 381 and 254 mm, respectively. Indiana has proposed changing their minimum length limit to 381 mm and allowing only one fish\u3e 889 mm to be harvested per day. My study examined the current status of flathead catfish in the Wabash River to determine a standardized sampling protocol and to provide management recommendations for Illinois. I sampled flathead catfish using AC and pulsed-DC electrofishing during the summer of 2010-2012. I also set hoopnets and trotlines in 2011, but only used hoopnetting in 2012. During 2010-2012, I collected 952 flathead catfish with a mean length and weight of 343±5.6 mm and 914.5±55.6 g, respectively. Mean age of the flathead catfish was 3.5±.07 years (range 0-9 years). Annually, flathead catfish relative weight was above 90% for the majority of gears used. Pulsed-DC electrofishing had the greatest catch per unit effort (28.2±2.3 fish/hour); howeverhoopnetting caught larger fish (hoopnet proportional size distribution (PSD)=88, pulsed-DC electrofishing PSD=40). Propportional size distribution indices were within target range to be consider as quality fisahery. My results suggest that a multiple gear approach including pulsed-DC electrofishing and hoopnetting is critical to adequately assess flathead catfish populations in large rivers. My total annual mortality estimate (Z=0.51) was similar to previous estimates (49-56 percent) for flathead catfish in Midwestern large rivers (Donabauer 2009, Kwak et al 2006). My yield per recruit model implies that at current minimum length limits, the flathead catfish fishery is not sustainable. However, uncertainty in Illinois recreational angler preferences and stock-recruitment dynamics of flathead 7 catfish may be required to better inform potential management changes. My findings, regarding mortality, high population PSD, healthy size structure, and evidence of recruitment by the presence of age-0 fish (Figure 10), suggest that the Wabash River flathead catfish population is healthy and is a sustainable resource unless characteristics of the fishery change greatly. A drastic change to the status of the population may render current fishing practices unsustainable