Impact of Gravel Bar Scalping on Neosho Madtom (Noturus placidus) Populations from the Lower Neosho River, Kansas

Abstract

ABSTRACT From 1996 to 2007 we sampled depositional point bars that were scalped for gravel harvesting and unharvested control sites in the Neosho River, Kansas to determine if scalping effected the abundance of the Neosho madtom (Noturus placidus) and other obligate benthic fishes. Mean relative abundance of the Neosho madtoms did not differ between scalped gravel scalped bars and control bars, but was greater in riffles and runs compared to deeper, low velocity point bars (P<0.001). Species diversity and richness of obligate benthic fishes tended to be similar between gravel scalped and control bars; however, some obligate benthic fishes [channel catfish (Ictalurus punctatus), freckled madtom (Noturus nocturnus), stonecat (Noturus flavus), orangethroat darter (Etheostoma spectabile), and suckermouth minnow (Phenocobius mirabilis)] were more likely to be present when the Neosho madtom was present (P<0.001). When combining additional data from other long-term monitoring from 1991 to 2007, Neosho madtom relative abundance in the Neosho River was positively related to mean annual flow (r=0.61, P=0.01). Scalping of gravel bars appeared to have less of an impact on Neosho madtom and other benthic obligate fishes than annual flow. However, other geomorphic metrics such as bedload transport were not measured in this study and, if affected by gravel scalping, may ultimately affect the fishes in the Neosho River.