Welcome to "Otoliths of North Sea Fish":

Interactive guide of identification of fish from the SE North Sea, Wadden Sea and adjacent fresh waters by means of otoliths and other hard parts.

Authors: Leopold M.F., C.J.G. van Damme, C.J.M. Philippart & C.J.N. Winter (2001).

The website allows identification of a large number of the common fish species from the North and Wadden Sea and their adjoining fresh water systems. Specific hard parts that dissolve only slowly can often still identify fish that have died and disintegrated. In bony fish, the 'ear-stones' or otoliths are particularly useful in this respect. Otoliths are made out of a very hard, calcareous material, are species-specific in their shape. Otolith size is often related to fish size. Thus, from an otolith, the species of fish and its size can be reconstructed if a good reference collection of otoliths of fish of the region can be consulted.
Otoliths may be retrieved from sediments, to reconstruct past fish fauna's, or from present-day fish predators (from stomachs or guts, regurgitates or faeces) to reconstruct their diets. For both lines of work, a referenced collection is now presented. The work contains electron microscopic photographs of otoliths of over 10,000 fish, comprising 90 species, collected in the North and Wadden Seas, as well as in some adjoining fresh waters. Data on some other hard parts, such as pharyngeal bones and chewing pads are also provided. Linked to the photographs are written accounts on identification, including special characters of the described items and pitfalls from similar species and wear of otoliths that have passed through a predator's gut; a database of regression equations relating otolith size to fish size and fish mass; and a database on known predators of that particular species of fish. Line drawings of the different fish species, as well as from 'standard' fish, fish otoliths, pharyngeal bones and chewing pads, showing how measurements were taken, are included.
After specific identification, it makes possible back-calculations of fish size and mass. The database on known predators puts identifications into a wider context of existing knowledge and will enhance confidence in identification or, in the case that the current predator was not earlier known as predator of the fish in question, form a check on the identification and add to the dissemination of new knowledge.

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