Determining fish origin by mining the otolith

Otoliths are commonly used as natural tags, yet current research focuses on trace element chemistry as the sole discriminatory factor in determining origin. Nursery areas can vary within systems and otoliths chronologically incorporate this information from both environmental and ontogenetic changes influenced by habitat. In this study, we consider a suite of parameters beyond trace elements from juvenile spotted seatrout (Cynoscion nebulosus) otoliths to give a comprehensive signature of seagrass habitats in the Chesapeake Bay. In addition to trace elements, we include oxygen and carbon stable isotopic composition to describe the oceanographic differences between areas. Additionally, we include juvenile growth rates to account for differences in habitat quality. We show that mining many parameters from a single otolith increases the resolution of the habitat signature. By extracting the full suite of life history information from the otolith, classification to natal seagrass beds is greater than discriminating using trace element chemistry alone. These methods have far reaching implications as classification to natal area is central to determining population structure in fish.