Columbia NFWCO setting a large trap net while sampling a Missouri River floodplain scour at the Overton Unit of Big Muddy NFWR

Fish Biologist Andy Plauck displays some nice largemouth bass captured during the scour hole sampling

Columbia National Fish and Wildlife Conservation Office (NFWCO) recently completed management recommendations for fisheries at the Overton Unit of Big Muddy National Fish and Wildlife Refuge (NFWR). The fisheries consist of three Missouri River floodplain scours created by the flood of 1993. These scours range from six  to 38 acres in size. They are unique from impoundment fisheries due to their almost annual reconnection to the river. Columbia NFWCO has monitored the scours since their creation and provided management recommendations to the refuge.

Through efforts with Big Muddy NFWR, the Missouri Department of Conservation (MDC), and the Genoa National Fish Hatchery (NFH), Columbia NFWCO has improved the fisheries in these scours. With the addition of tree reefs they have created recruitment habitat for young sportfish. With these partnerships they have also performed several supplemental fish stockings of channel catfish, largemouth bass, and redear sunfish.

Each year’s sampling has been used to evaluate the effects of stockings and reconnection. Data suggest remnant sportfish populations remain after reconnections and supplemental stockings are needed to maintain the populations. Sportfish reproduction is occurring in the scours but due to emigration and possibly angler harvest the stockings are still needed. It is yet to be seen if overstocking is possible. Future recommendations include additional stockings of sportfish and long term monitoring of riverine fish (e.g. flathead catfish and freshwater drum) and exotic invasive species (e.g. silver and bighead carp) found after reconnection. These efforts support the Partnerships and Accountability and Public Use goals of the Fisheries Programs Vision for the Future.