Validation of Annulus Formation in Otoliths of Notchlip Redhorse (Moxostoma collapsum) and Brassy Jumprock (Moxostomasp.) in Broad River, South Carolina, with Observations on their Growth and Mortality

Abstract

Moxostoma collapsum (Notchlip Redhorse) and the undescribed Moxostoma sp. (Brassy Jumprock) form a large component of the fish assemblage in the Broad River, SC, but little is known about their population characteristics, nor has an aging method been validated for either species. We validate that one annulus is formed each year in the lapillus otolith of the two species and identify spring as the period of annulus formation, using chemical marking and marginal increment analyses, respectively. Notchlip Redhorse and Brassy Jumprock are long-lived, with observed maximum estimated ages of 17 and 21, respectively. Both species grow quickly during their first few years; little growth occurs after age 7. Instantaneous total mortality of each species was low (Z ≤ 0.35), suggesting there is little exploitation of either species in the Broad River, SC.