Chemical Composition of Fish Hard Parts as a Natural Marker of Fish Stocks

The chemical composition of calcified structures in fish (otoliths, spines, rays, scales, and vertebrae) has been identified as a useful natural marker of stock structure. This application depends on geographic variation in water chemistry or other factors (e.g., temperature) that influences the chemistry of the calcified structure such that fish that inhabit different environments exhibit differences in their chemical signature. The use of this technique in stock discrimination requires that a number of assumptions must be met, including that groups of interest possess characteristic and reproducible markers and all possible groups contributing to the group mixture have been characterized. In some instances, structural chemistry can permit observation of subtle population structure that may not be detected by genetic applications alone. Chemical analysis of calcified structures is most effective when used as part of a holistic approach to stock identification.