The response of Virgin River Chub, Gila seminuda, to flooding in the Muddy River (Clark County, Nevada, USA)

Authors: Rogers, Ron*, Albrecht, Brandon, Kegerries, Ron, Mohn, Harrison, Syzdek, David

Year: 2015 (xlvii)

Abstract

BIO-WEST Inc., in cooperation with the Southern Nevada Water Authority, documented a decline in the Gila seminuda relative abundance from 2007-2014 in the Muddy River (river kilometer 23.7-49.1). The decline in relative abundance was seemingly caused by an aging population combined with no detectable recruitment. Evidence to support an aging population in decline, includes significant decreases of catch per unit effort, a significant increase in mean total length, and an absence of size class distribution. However, floods in desert rivers can benefit the native fish community in several ways including creating new habitats for native species to occuppy, reduce nonnative competitors, modify substrates to create spawning and foraging habitat, as well as other physical alterations to the river channel. In the September 2014 a large flood occurred in the Muddy River, followed by a spawning pulse of G. seminuda in 2015. Elevated numbers of small, wild G. seminuda and multiple size classes were detected during spring and fall 2015 long term monitoring efforts, suggesting that recruitment may be occurring in the Muddy River. This response has been observed in the native fish community in the neighboring Virgin River, and promising sign for the Muddy River G. seminuda population.