Precision of Five Calcified Structures for Grass Carp Age Estimation

Estimating individual age is important for defining the structure of fish populations (i.e., recruitment, growth, and mortality), including the assessment of many management objectives. Knowledge of the relative precision of age estimates using standard calcified structures is required to estimate the age of Grass Carp. Therefore, our objective was to evaluate the precision of annuli counts among two lethal (i.e., sectioned lapilli otoliths and vertebrae) and three non-lethal (i.e., anterior sinistral and dextral pectoral fin rays and anterior dorsal fin rays) calcified structures. Precision was evaluated by calculating percent exact agreement (PA), agreement within one year (PA ± 1 year), three year (PA ± 3 years) and coefficient of variation (CV) among annuli counts. Grass Carp (N = 71) were collected during 2024 and 2025 by state, federal, and commercial harvesters from pools 8, 10, and 19 of the Upper Mississippi River. Agreement between two independent readers was highest for the sectioned vertebrae, followed by sectioned pectoral fin rays, dorsal fin rays, and lapilli otoliths. Lethal methods for age estimation were more precise (i.e., vertebrae); however, sinistral or dextral pectoral fin rays may be an effective non-lethal approach with similar agreement if live release is warranted. This data provide clarity about possible age biases among different lethal and non-lethal calcified structures that have been commonly used to estimate the age of Grass Carp within invaded systems.