Using meristic and morphometric techniques to identify juvenile Catostomus suckers (Largescale Sucker C. macrocheilus, Longnose Sucker C. catostomus, White Sucker C. commersonii – Teleostei: Cypriniformes: Catostomidae) within the Peace River watershed, Alberta

Catostomid suckers are an important but understudied component of North American freshwater ecosystems. Alberta populations of Catostomus macrocheilus Girard, 1856; Catostomus commersonii (Lacepède, 1803); and Catostomus catostomus (Forster, 1773) have yet to be described for common meristic phenotypes and can be difficult to differentiate as juveniles. Given the relative rarity of C. macrocheilus in Alberta, site-specific phenotypic data is needed to ensure proper long-term monitoring of this species. Sample populations of juveniles from the Peace River Drainage were acquired and assessed for meristic data including the fin rays, lateral line scale series, and vertebrae. Additionally, mouth shape differences were recorded between the three Catostomus species. Meristic data were analyzed through a series of non-parametric Mann–Whitney U tests and a Principal Component Analysis, while morphometric data was analyzed using a Canonical Variate Analysis, a Procrustes ANOVA, a Discriminant Function Analysis (DFA), and a cross-validation test. Results indicated statistically significant differences between species at several meristic features, with the number of dorsal fin rays being the most useful metric for species-level field identification. Furthermore, mouth shape was determined to be significantly different between all species, but was most distinct for C. commersonii. This study contributes to an improved understanding of catostomids in Alberta, provides statistically significant identification methods, and helps establish a baseline for future evolutionary research which will inform conservation.