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The nitrogen isotopes (δ¹⁵N) in the organic fraction of accretionary hard part structures, such as fish otoliths, may provide life histories of dietary change. We performed controlled experiments to validate the dynamics of the isotopic signal incorporation into biominerals following dietary shifts and also compared whole-otolith and serial sampling approaches for diet reconstruction. Laboratory-reared Atlantic croaker (Micropogonias undulatus) were switched from a high quality, high δ¹⁵N diet (δ¹⁵N = 10.7‰) to one of two lower quality, lower δ¹⁵N diets (δ¹⁵N = 5.9 or 3.7‰). Using the oxidation-denitrifier method, including cleaning protocols required for fossil otoliths, we measured both otolith-bound δ¹⁵N (δ¹⁵N_oto) of whole-otolith subsamples (δ¹⁵N_whole) and sequentially micromilled otolith powders (δ¹⁵N_micro) and compared these results to white muscle tissue and liver δ¹⁵N obtained through traditional …