Can Amino Acid Racemization Be Utilized for Fish Age Validation?

We investigated the relationship between aspartic acid D:L ratios and otolith-derived age estimates in Gulf of Mexico red snapper, Lutjanus campechanus, (ages 1-26 y; R^2 = 0.89) and Caribbean yellowtail snapper, Ocyurus chrysurus (ages 2-17 y; R^2 = 0.84). The estimated racemization rate was 0.61 x 10^-3 y^-1 for red snapper and 1.28 x 10^-3 y^-1 for yellowtail snapper, reflecting temperature differences between study regions. Mean jackknifed error in ages predicted from aspartic acid D:L was 1.70 ± 0.39 y for red snapper and 1.57 ± 0.41 y for yellowtail snapper. Results suggest amino acid racemization may be an effective tool for direct age estimation and potentially age validation, in fishes.