In Catostomus fishes (suckers) in the Upper Colorado River basin (Colorado, Wyoming, and Utah, USA), complex hybridization dynamics involving six different parental species lead to extremely variable genomic outcomes of hybridization. I quantified variation in hybridization among Catostomus species at >20 locations in the Upper Colorado River basin in Wyoming and Colorado (Mandeville et al. 2015, Molecular Ecology; Mandeville et al. in press, Evolution Letters), using high resolution genomic data from 2,785 individuals. Contact between Catostomus species resulted in hybridization and extensive backcrossing in some rivers, and no hybridization or limited hybridization in others, despite co-occurrence of parental species. Similarly, some rivers contained many different hybrid crosses, while other rivers contained a single cross or no hybrids.