Determination of the emaciation state of the glass eels (Anguilla anguilla) in migration in coastal and estuarine areas).

The objective of this work is to characterise the variations fo the quality of the glass eels recruitment during a season of migration, from November till March and before and after the transition from marine to continental e nvironment. The emaciation state measured from the ratio DNA/Dry weight and percentage of body water is analysed from a sampling of glass-eels collect ed at sea and in estuary, in the South of the Bay of Biscay during the migr ation period 1999/2000. The length and the mass are taken into account, the y decrease during the season while the individuals are more and more pigmen ted. However, our work shows that groups of glass eels arriving on the coas ts of the Bay of Biscay are homogeneous from the point of view of their ene rgetic and hydride reserves with a high individual variability within these groups. Also no significant difference in losses of water and energetic re serve were observed among the individuals migrating at the beginning and du ring tide stream. Fluctuations of the biochemical indication and the percen tage of water between the glass eels caught in sea and in estuary show that the transition between maritime and continental environment is not a mobil ising event of a lot of energy for glass eels. Differences were only observ ed in December. (C) 2001 Academie des sciences Editions scientifiques et me dicales Elsevier SAS.