Estimating the Ages of Black Hills Mountain Suckers: Precision, Population Dynamics, and Management Implications

Although Mountain Suckers are considered secure across their range, they are listed as a species of greatest conservation need in some parts. Research has not identified which calcified structure yields the most precise age estimates for Mountain Sucker and little is known about their population dynamics. We compared four calcified structures to identify which structure provided the most precise age estimates for Mountain Sucker and subsequently quantified recruitment, age and size at maturation, growth, and mortality for one population of Mountain Sucker in the Black Hills, South Dakota. Polished otoliths had the highest precision of the four structures used, followed by sectioned pectoral fin rays. Recruitment of Mountain Sucker was consistent; maturation began at age-3 and nearly all fish were mature by age-5. Mountain Sucker reached 100 mm total length (TL) during their fourth growing season and reached an average maximum attainable size of 219 mm TL. Natural mortality was 25% in the Black Hills. We recommend using polished otoliths to estimate the ages of Mountain Sucker or sectioned pectoral fin rays if a non-lethal structure is desired. Knowledge of Mountain Sucker population dynamics will help with management of this species throughout its range, especially where it’s rare or declining.