Marie-Noelle De Casamajor

Détermination de lˈétat dˈamaigrissement des civelles (Anguilla Anguilla) en migration en zones côtière et estuarienne

The objective of this work is to characterise the variations of 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 environment. The emaciation state measured from the ratio DNA/Dry weight and percentage of body water is analysed from a sampling of glass-eels collected at sea and in estuary, in the South of the Bay of Biscay during the migration period 1999/2000. The length and the mass are taken into account, they decrease during the season while the individuals are more and more pigmented. However, our work shows that groups of glass eels arriving on the coasts of the Bay of Biscay are homogeneous from the point of view of their energetic and hydride reserves with a high individual variability within these groups. Also no significant difference in losses of water and energetic reserve were observed among the individuals migrating at the beginning and during tide stream. Fluctuations of the biochemical indication and the percentage of water between the glass eels caught in sea and in estuary show that the transition between maritime and continental environment is not a mobilising event of a lot of energy for glass eels. Differences were only observed in December.

Passé larvaire des civelles, Anguilla anguilla (Linné, 1758) en migration en zones côtière et estuarienne (Adour, golfe de Gascogne) à partir de l'examen des otolithes

Abstract The embryonic past of glass eels was studied from the interpretation of microstructures registered on otoliths. The aim of this work is to put in evidence possible seasonal modifications of the growth of otoliths so that differences between otoliths of glass eels caught off marine and estuarine environment. So during the season 1999–2000, from November till March, otolith sampling was realised in the southwestern part of France, in an estuarine and coastal zone. We observed a spatial and temporal evolution of proportions of the three various types of otoliths taken into account. Glass eels sampled at sea sometimes have a mark on their otoliths indicating the transition in the estuary, especially at the end of the fishing season. Measures of growth marks of otoliths showed that there were no seasonal differences during phases of the transoceanic migration and the crossing of the continental shelf. The radius of otoliths of glass eels sampled at sea was significantly smaller than those sampled in estuary. These results translated homogeneous environmental modifications met by the various larvae groups during the oceanic crossing and during the principal migration season as well as a turn over of these groups during the transition between marine and continental environment.The embryonic past of glass eels was studied from the interpretation of microstructures registered on otoliths. The aim of this work is to put in evidence possible seasonal modifications of the growth of otoliths so that differences between otoliths of glass eels caught off marine and estuarine environment. So during the season 1999-2000, from November till March, otolith sampling was realised in the southwestern part of France, in an estuarine and coastal zone. We observed a spatial and temporal evolution of proportions of the three various types of otoliths taken into account. Glass eels sampled at sea sometimes have a mark on their otoliths indicating the transition in the estuary, especially at the end of the fishing season. Measures of growth marks of otoliths showed that there were no seasonal differences during phases of the transoceanic migration and the crossing of the continental shelf. The radius of otoliths of glass eels sampled at sea was significantly smaller than those sampled in estuary. These results translated homogeneous environmental modifications met by the various larvae groups during the oceanic crossing and during the principal migration season as well as a turn over of these groups during the transition between marine and continental environment.

Bioindicateurs d'impact dans les ports et les estuaires: les foraminifères

ABSTRACT This work is based on about 2,000 samples. It provides a synthetic description of the distribution patterns of foraminiferal assemblages in paralic environments and shows on two examples the effect of human activities on these assemblages. It shows that despite the great diversity of ecological parameters, foraminiferal assemblages are naturally distributed along a few major gradients. Anomalies in this distribution pattern and/or morphological abnormalities of the tests indicate anthropogenic or natural stresses. An increase in the number of individuals, specific richness and test size indicates organic pollution while chemical pollution has an inverse effect. A high dominance of Cribroelphidium excavatum and to a lesser extend of Haynesina germanica may indicate areas subjected to a strong chemical impact while the bolivinids have their maximum relative abundance in the fine sediments of the marina.

Passé larvaire des civelles, Anguilla anguilla (Linné, 1758) en migration en zones côtière et estuarienne (Adour, golfe de Gascogne) à partir de l’examen des otolithesLarval history of glass eels, Anguilla anguilla, (Linné, 1758) in migration in coastal and estuarine areas (Adour, Bay of Biscay) as revealed by otolith structure.

Abstract The embryonic past of glass eels was studied from the interpretation of microstructures registered on otoliths. The aim of this work is to put in evidence possible seasonal modifications of the growth of otoliths so that differences between otoliths of glass eels caught off marine and estuarine environment. So during the season 1999–2000, from November till March, otolith sampling was realised in the southwestern part of France, in an estuarine and coastal zone. We observed a spatial and temporal evolution of proportions of the three various types of otoliths taken into account. Glass eels sampled at sea sometimes have a mark on their otoliths indicating the transition in the estuary, especially at the end of the fishing season. Measures of growth marks of otoliths showed that there were no seasonal differences during phases of the transoceanic migration and the crossing of the continental shelf. The radius of otoliths of glass eels sampled at sea was significantly smaller than those sampled in estuary. These results translated homogeneous environmental modifications met by the various larvae groups during the oceanic crossing and during the principal migration season as well as a turn over of these groups during the transition between marine and continental environment.The embryonic past of glass eels was studied from the interpretation of microstructures registered on otoliths. The aim of this work is to put in evidence possible seasonal modifications of the growth of otoliths so that differences between otoliths of glass eels caught off marine and estuarine environment. So during the season 1999-2000, from November till March, otolith sampling was realised in the southwestern part of France, in an estuarine and coastal zone. We observed a spatial and temporal evolution of proportions of the three various types of otoliths taken into account. Glass eels sampled at sea sometimes have a mark on their otoliths indicating the transition in the estuary, especially at the end of the fishing season. Measures of growth marks of otoliths showed that there were no seasonal differences during phases of the transoceanic migration and the crossing of the continental shelf. The radius of otoliths of glass eels sampled at sea was significantly smaller than those sampled in estuary. These results translated homogeneous environmental modifications met by the various larvae groups during the oceanic crossing and during the principal migration season as well as a turn over of these groups during the transition between marine and continental environment.