Potential Effects of Age, Population, and Latitude on Precision of Scale and Otolith Age Estimates of White Crappie in Minnesota

Abstract

Abstract We calculated between-reader precision of ages estimated with scales and whole otoliths (sagittae) of White Crappie Pomoxis annularis for 10 Minnesota populations, and determined effects of population and mean age on precision. For all samples combined, two experienced readers counted the same number of annuli on 91% of the scales and 92% of the whole otoliths. Mean coefficients of variation equaled 1.8% between scale readers and 3.0% between whole otolith readers. We detected no systematic age-bias between readers of each structure. Agreement between scale readers differed among populations, ranging from 67 to 100% among populations (median = 89%), but agreement also decreased with increasing scale age in six of these populations. Agreement between readers of whole otoliths was unaffected by increasing age of White Crappie, but agreement ranged from 39 to 100% among populations. When compared with other studies, latitude had no influence on precision of whole otolith ages because precision in the Minnesota populations differed little from precision reported for populations in Kentucky and Mississippi. Latitude could be affecting precision in scale age estimates because precision was usually better for the Minnesota populations than for populations in Oklahoma, Kentucky, and Mississippi; however, differences in viewing methods and reader competencies could also explain geographical differences.