Mean age and migration patterns of Anguilla anguilla (L.) glass eels from three French estuaries (Somme, Vilaine and Adour Rivers)

Glass eels were sampled, according to the 1991 EIFAC Working Party recommendation (Anon., 1991), in three estuaries, about 800 km apart along the French coast. Only preliminary data are presented here for the peak of immigration in February - March 1992. Biometrics, otolith structure and estimates of larval duration lead to several assumptions on the early life dynamics. Results show that: i) the body size, the otolith development and the mean age are not correlated with the latitude; ii) the migration over the continental shelf is not reflected in the otolith proportionally to the shorter distance from the shelf edge to the estuary; iii) marginal structures of the otolith could be related to the delay before entering freshwater.