Estimating the Ages of Mountain SuckerCatostomus platyrhynchusfrom the Black Hills: Precision, Maturation, and Growth

Abstract

Although mountain sucker Catostomus platyrhynchus is considered secure across its range, it has declined in parts of its range and is listed in South Dakota as a species of greatest conservation need. To our knowledge, no research has identified which calcified structure provides the most precise age estimates for mountain sucker, and little is known about mountain sucker population dynamics. To identify which structure provided the most precise age estimates, we compared age estimates from scales, sectioned pectoral fin rays, whole asteriscus otoliths, and polished asteriscus otoliths collected from 110 mountain sucker from 2 creeks in the Black Hills of South Dakota. Additionally, we quantified growth, age, and size at maturation for one population of mountain sucker in the Black Hills. Polished otoliths had the greatest precision of the 4 structures used, followed by sectioned pectoral fin rays. Mountain sucker reached an average size of 100 mm total length (TL) during their fourth growing season and reached an average maximum attainable size of 219 mm TL. Mountain sucker began to mature at age 3, with nearly all being mature by age 5. In the Black Hills, the shortest mature male was 95 mm TL and the shortest mature female was 101 mm TL. We recommend using polished otoliths to estimate the ages of mountain sucker. If a nonlethal structure is desired to estimate the ages of mountain sucker, we recommend using sectioned pectoral fin rays. Future research should be directed to fill the many knowledge gaps in the biology and ecology of mountain sucker (e.g., juvenile habitat use in the Black Hills). As these knowledge gaps are addressed, management actions could be taken to conserve this species in the parts of its range where it is declining.