Otolith Chemistry Distinguishes the Estuarine Nurseries of Summer Flounder

The summer flounder is an important fisheries species along the US east coast. Juvenile summer flounder use the east coast estuaries as nursery grounds during the summer, thereby incorporating chemical signatures unique to the estuary within their calcified structures. Otolith chemistry is a widespread technique that uses these signatures to answer many questions related to life history and stock structure. We test the hypothesis that the chemical signatures in the otoliths can be used to differentiate between estuaries. We used Laser-ablation inductively-coupled plasma mass spectrometry to analyze ⁷Li, ²⁵Mg, ⁴⁸Ca, ⁵⁵Mn, ⁸⁵Rb, ⁸⁸Sr, ⁸⁹Y, and ¹³⁸Ba, and an automated Isoprime Micromass carbonate analyzer for stable isotopes δ¹³C and δ¹⁸O. A multivariate analysis of variance showed that there are area-scale differences in the overall chemical signatures, while univariate ANOVA’s showed that those differences resided in all of the studied elements. Discriminant function analyses on all possible combinations of elements showed that a five-variable model utilizing Li, Mg, Y, C, and O provides the highest classification accuracy. We conclude that otolith chemistry in general and the discriminant functions obtained in particular are useful tools in distinguishing between summer flounder growing in the different estuaries along the US east coast.