Comparison of lethal and non-lethal aging structures for Largemouth Bass and influence of reader experience

Abstract

Accurate and precise estimates of fish age are crucial for calculating dynamic rate functions of a fishery that aid in making management decisions. Otoliths are often the preferred structure used when aging fish, as they typically provide accurate and precise age estimations. However, non-lethal alternatives need to be explored for when sacrificing specimens for age and growth data is not desired. Metrics of bias and precision are often compared to assess differences in aging structures, but the influence of reader experience and subjectivity on these metrics has not been well-studied. We assessed bias and precision between whole-viewed sagittal otoliths, scales, dorsal fin spines, and anal fin spines of Largemouth Bass Micropterus nigricans, and compared metrics of bias and precision between experienced and inexperienced readers. Inexperienced readers produced higher coefficient of variation values across nearly all structures compared to experienced readers. However, reader experience had a negligible influence on accuracy, which varied between structures. Our results indicate that incorporating quality control and training protocols into aging analysis could increase precision and decrease bias. Age estimations obtained from sectioned sagittal otoliths were the most precise and are recommended for aging analysis if sacrificing the specimen is acceptable. Age estimate precision from scales was similar to that from anal fin spines, but scales provided better accuracy. Therefore, we recommend the continued use of scales as non-lethal aging structures in Nebraska. It would be prudent for researchers in other regions to assess bias and accuracy limitations of aging structures from local Largemouth Bass fisheries to determine which structure best suits their purposes.