Comparison of Otolith and Pectoral Fin Spine Ages of Black Bullhead Ameiurus melas

Abstract

Black bullhead Ameiurus melas are an environmentally tolerant fish that are often the target of population-level management efforts due to overabundance and potential negative influences on sport fishes. Descriptions of black bullhead growth and life history have been limited in part due to challenges in age estimation. Pectoral fin spines have been validated as age estimation structures for other ictalurids, but not black bullhead. We evaluated the precision of black bullhead pectoral fin spine and whole otolith age estimates from a northern Wisconsin lake. Age bias of pectoral fin spines was evaluated relative to whole otoliths using age estimates from two readers. Age estimates from both structures were applied to produce von Bertalanffy growth models. Precision of both structures was similar for both readers (66% and 58% agreement, 89% and 87% within 1 year). Pectoral fin spine age estimates showed higher between-reader agreement (59%, 95% within 1 year, CV = 9.2) than whole otolith age estimates (45%, 91% within 1 year, CV = 15.1). Pectoral fin spines may underestimate age relative to whole otoliths, particularly in older fish. von Bertalanffy growth model parameters were similar using both structures. Our findings suggest pectoral fin spine and whole otolith age estimates provide utility for age estimation in black bullhead, but modified methods of otolith processing and known age fish are needed to evaluate the accuracy of each structure.