Numerous metal pollutants naturally find their way into estuaries, where many of them build up in the bodies of fish. While otoliths can give a historical record of pollution exposure, metal concentrations in soft tissue and water samples require ongoing, long-term sampling procedures. Fish have otoliths, which are three pairs of ear bones called the sagitta, lapillus, and asteriscus. The chemical makeup of these otoliths can be a useful tool to determine the presence of hazardous substances in fish because the physiological activity of fish is controlled by a variety of environmental factors. The possible use of otoliths as inorganic tracers of metal contamination will be covered in this chapter.