Population fragmentation and white sucker introduction affect populations of bluehead suckers, flannelmouth suckers, and roundtail chubs in a headwater stream system, Wyoming

Abstract

I evaluated the effects of human-made instream structures on populations of bluehead sucker Catostomus discobolus, flannelmouth sucker Catostomus latipinnis, and roundtail chub Gila robusta in Muddy Creek, Carbon County, Wyoming. Movements and population features were assessed among adjacent segments partitioned by three instream structures. Instream structures prevented or severely limited upstream movements, but downstream movements over structures occurred. Within each segment, roundtail chubs were most abundant and flannelmouth suckers were least abundant among the three native species. A core population of the three native species existed in one segment and supported the highest densities of juveniles and adults and the broadest length ranges. Non-native white suckers Catostomus commersoni were the most abundant species in the study area, their highest densities occurred in altered habitat and substantial hybridization with the two native catostomid species was evident. Native fish populations in the most upstream segment may be at risk of extirpation due to low abundance and reproduction. Connectivity among habitats is required to carry out the life cycles of native fishes and fragmentation by human-made structures is affecting their abundance and distribution patterns.