Nonlethal, Epigenetic Age Estimation in a Freshwater Sportfish, Florida Bass (Micropterus salmoides)

Black basses (Micropterus spp.) are the most popular freshwater sportfishes in North America, with high recreational, societal, and economic value. The conservation and management of black bass fisheries rely on the generation of age data to estimate population dynamics. Age data are typically produced via counts of opaque zones in otolith sections, a necessarily lethal process. The development of an accurate, nonlethal age estimation method would expand opportunities for collecting age-related information in cases where sacrificing fish is either not an option (e.g., tournaments) or undesirable (e.g., trophy-sized fish). An epigenetic clock was developed for Florida bass (Micropterus salmoides) using DNA extracted from fin clips and enzymatically converted restriction site-associated DNA sequencing (EC-RADseq). CpG sites exhibiting age-correlated DNA methylation were identified using Bayesian generalized linear models in individuals (n = 176; age range: 0.84-13.21 years) captured from six different water bodies across Florida, USA, and potential environmentally influenced, age-predictive sites were identified and removed. The epigenetic clock developed using elastic net regression was highly accurate (mean absolute error, MAE = 0.28 years) and precise (R ² = 0.98). Overall, results demonstrate an accurate, nonlethal alternative to otolith-based age determination of Florida bass and could likely be applied to other black basses. In addition, when compared to traditional age estimation via hard structures, epigenetic age estimation is relatively rapid and cost-effective, with important implications for black bass assessment, management, and conservation.