Evaluating the efficacy of an intervention on reducing Catostomus hybridization

Background/Question/Methods

Non-native species are a leading threat to biodiversity. They pose risks to native populations through competition, predation, disease, and hybridization. Often driven by anthropogenic influences, native and non-native species can hybridize to the detriment of the imperilled native species. Catostomus fishes in the Upper Colorado River Basin are an example of this. Recent evidence has shown extensive hybridization between non-native white suckers (C. commersonii) and native flannelmouth and bluehead suckers (C. latipinnis and C. discobolus). This system provides a suitable model for testing the efficacy of an intervention to reduce the abundance of non-native species and their hybrids. This study implements a Resistance Board Weir (RBW) as a fish barrier across Roubideau Creek, a tributary of the Gunnison River in Colorado (USA), to restrict non-native fish access to spawning habitat. Conducted over four years, the study gathers genetic data from larval species, pre- and post-implementation of the RBW. Genetic evidence allows us to determine the efficacy of a RBW at controlling non-native species. In addition, geographic data collected alongside larval fish allows for analysis of spatial spawning preferences in both native and non-native suckers. Combined this information can help provide the most accurate recommendations regarding conservation management interventions going forward.

Results/Conclusions

We captured a subset of spawning adults and their progeny (larval fish) in 2019 through 2022 and used tissue samples to extract DNA and generate high resolution genomic data. Preliminary analyses of genomic data show that hybridization is extensive in this region pre-implementation of the Resistance Board Weir in 2021. We expect that the abundance of white suckers and their hybrids will decrease significantly during years of controlled access. Additionally, it is expected that native larval fish will be found in a higher abundance upstream, compared to non-native and hybrid larval fish, consistent with current field observations in this system as well as with other similar studies. This work will contribute novel information to understanding how effectively conservation efforts using fish barriers can reduce non-native species and prevent hybridization.