Biological and physiological characteristics of glass eels (Anguilla anguilla) in the Bay of Biscay

Abstract

The purpose of this work was to characterize the quality of glass-eel recruitment during season of migration and transition from the marine to the continental environment. Glass eels were sampled, in the south of the Bay of Biscay from November 1999 to March 2000. The individual degree of slimming was measured from the ratio DNA/dry weight and the water content. The larval history was studied by interpretation of the microstructures registered on the otoliths. During the sampling season, glass eels changed in pigmentation and length and weight decreased. Their energy and water budget remained constant but large individual variations inside each groups were observed. A slimming between glass eels captured at sea and in estuary was observed in December only whereas they were not pigmented. Samples of glass eel otoliths collected on different areas and periods presented microstructural differences. The otoliths of glass eels caught at sea in February presented a smaller radius and a transition mark in estuary. Monthly measurements of growth zones of otoliths showed a similar larval history during the transoceanic migration. These results indicate a mixing of flows of the glass eels between the marine and continental environment at the end of sampling season. © 2002, The Japanese Society of Fisheries Science. All rights reserved.