The otolith, a calcified part in the inner ear of fish, evolves throughout the life of an individual and is generally used to estimate its age. So how do we analyze this tiny mineral particle, and what does it tell us about each species of fish? This book provides a three-dimensional (3D) description and analysis of the otolith shape of the main commercial species in the English Channel and North Sea. This innovative approach, made possible by the use of an X-ray microtomograph, makes it possible to specify otolith characteristics, differentiate fish populations and locate them geographically. Flatfish such as sole, dab, plaice and turbot, and roundfish from herring to haddock and gurnard, for each species, five individuals representative of the size range sampled in the marine environment have been selected and their otolith shape described. An invaluable resource for fisheries science, this guide offers researchers, professionals and technicians a new way of refining their knowledge of Channel and North Sea species and individuals.