A fish otolith is the ear stone of a fish. Otolith are widely used for determining the age of fish. Usually, the internal otolith structure is examined. In thin-sections of an otolith, ring-like zones - like the year rings of a tree - may become visible. However, preparations are rather time-consuming and therefore expensive. Also, there is quite some room left for subjective judgements by the so called reader.

This is where otolith shape analysis comes in. While different readers may draw different conclusions on the same sample, it can be expected from a fully computerised system that such uncertainties are minimised or even avoided.

The otolith shape can be obtained unambiguously from digital images. The raw data is then introduced into highly sophisticated image analysis programs which extract relevant shape descriptors and use these against a database to find matches. If proper age-group reference databases, e.g. for different species or different habitats, are available, the identification can be performed in an almost automatic fashion.