Evaluating the Effectiveness of Large Scale Electrofishing Removal to Conserve the Three Species in Wyoming

Non-native fish removal efforts were conducted in 2009 and 2010 via backpack and cataraft electrofishing to benefit bluehead suckers Catostomus discobolus, flannelmouth suckers Catostomus latipinnis, and roundtail chub Gila robusta in three priority drainages: the Big Sandy River, Little Sandy Creek, and Muddy Creek within the upper Green River and Little Snake River watersheds in southern Wyoming.  These native fishes are endemic to the Colorado River basin and are affected by competition, predation and hybridization from non-native fishes in the priority drainages.  Throughout removal efforts, 1,307 burbot Lota lota, 25,248 white suckers Catostomus commersoni, 2,401 flannelmouth-white sucker hybrids, 303 bluehead-white sucker hybrids, 1,104 longnose suckers Catostomus catostomus and 2,532 creek chub Semotilus atromaculatus were removed from over 155 river miles within the priority drainages.  We examine differences in population structure between the two years.  Results indicate that differences in population structure exist for most species between 2009 and 2010.  Removal efforts had positive influences on native fish populations, while decimating non-native fishes.  Length frequency histograms suggest that continued recruitment is occurring in native fish populations in Little Sandy Creek and Muddy Creek.  Recruitment is also apparent in the Big Sandy River where successful recruitment of native fishes has not been documented in several years.  Non-native fish populations are in decline in the Big Sandy River and Muddy Creek.