Sampling Statistics and Size Distributions for Flathead Catfish Populations in Four Missouri Rivers

摘要

Flathead catfish Pylodictis olivaris are native to Missouri and comprise one of the most important recreational and commercial fisheries in Missouri. Our specific study objective was to describe catch statistics for flathead catfish populations in moderate-large rivers in Missouri to provide sampling guidance for fisheries managers where a paucity of information existed. We used low-frequency (15 Hz) DC electrofishing and hoop nets in segments of the Grand, Lamine, and Platte rivers and pools 20-22 of the upper Mississippi River (UMR) during April-July 2006-2007. Electrofishing mean catch per unit effort (CPUE) ranged from 13.1 (Lamine) to 116.6 (UMR) fish/h while hoop-net mean CPUE ranged from 0.131 (Lamine) to 0.694 (Grand) fish/hoop-net-night. Length distributions showed that hoop nets caught a higher relative abundance of flathead catfish over 40 cm total length (TL) compared to electrofishing, most notably in the Grand and Platte rivers, whereas electrofishing caught relatively more flathead catfish under 35 cm TL in all rivers compared to hoop nets. Our results indicate that a combination of low-frequency (15 Hz) electrofishing and hoop nets should be used during the period of April 15 through July 15 to best represent length structure and relative abundance of flathead catfish populations in these rivers. More specifically, we found low-frequency electrofishing to be most effective for stock size and larger flathead catfish during mid-April to mid-June; however, these results were not as conclusive in 2007. As popularity and angling pressure of these fisheries increases, our results will provide managers with sampling guidance and baseline information in efforts to develop high-quality flathead catfish populations in selected rivers.