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Abstract

Mountain Sucker Catostomus platyrhynchus is considered secure across its range, it has been declining in parts of its range, and is listed as a species of greatest conservation need in South Dakota. To our knowledge, no research has identified which calcified structure yields the most precise age estimates for Mountain Sucker and little is known about Mountain Sucker population dynamics. We compared scales, sectioned fin rays, whole otoliths, and polished otoliths to identify which structure provided the most precise age estimates for Mountain Sucker in the Black Hills of South Dakota. Additionally, we quantified recruitment, growth, age and size at maturation, and mortality for one population of Mountain Sucker in the Black Hills. Polished otoliths had the highest precision of the four structures used, followed by sectioned pectoral fin rays. Recruitment of Mountain Sucker was consistent with many strong year classes present. Mountain Sucker reached 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. Natural mortality was estimated to be 25% in the Black Hills. We recommend using polished otoliths to estimate the ages of Mountain Sucker. If a non-lethal structure is desired to estimate the ages of Mountain Sucker, we recommend using sectioned pectoral fin rays. Despite being listed as a species of greatest conservation need in South Dakota, some populations of Mountain Sucker in the Black Hills are stable. Future research should be directed to fill in the many knowledge gaps in the biology and ecology of Mountain Sucker. As these knowledge gaps are filled, management actions could be taken to conserve this species in the parts of its range where it is declining.

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