Origine et caracteristiques de la distribution de l'ombre commun, Thymallus thymallus (L., 1758) en Europe et en France

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Summary

The natural distribution of the grayling, Thymallus thymallus (L.), includes the central and northern countries of Europe. If its presence in many of them, especially in the northern part of the continent, is a consequence of the recent ice-cover, its distribution in central Europe has an earlier origin and is the result of the connection between the Rhone, the Rhône and the Danube at the end of the Tertiary era.

The presence of an isolated population in the Loire drainage basin is more difficult to explain. The grayling never spontaneously occurred in the Seine or Garonne rivers, and the Loire population can only draw its origin from the Rhone river, in spite of the fact that no such connection is known to have existed since the end of the Tertiary era. This seems to confirm the rather early presence of the grayling in Europe. No other fish shows a present distribution similar to that of the grayling, except perhaps the burbot (Lota lota L.), but the natural area of our fishes has been modified by the construction of the canals during the XVIII^th century.