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The spring distribution of larval fish stages of flatfishes in the Dover Strait (eastern English Channel) was studied in 1995 and 1999. Fish larvae were identified and sorted according to developmental stages in order to study their ontogenic distribution. The French coastal waters are characterised by an unstable tide-dependent front, which influences larval dispersion. In spring, the French coastal waters have a high phytoplanktonic production. They have higher temperatures, lower salinities and differences in current intensity compared with the central English Channel waters. Generalised Additive Models (GAM) combined with Geographic Information Systems (GIS) were used to model the potential habitats of life stages considering data from three major surveys in this area. The models were developed by coupling presence-absence models with non-null abundance models. The potential habitat of larval stages was then mapped using a geostatistical method (kriging). This revealed different species strategies in which young stages were abundant in central waters and older ones were distributed mainly along the French and Belgian coasts. It is concluded that the central English waters are important for young stages after hatching and that coastal waters are essential nurseries for future juveniles. The models of three flatfish species having similar life cycle strategies are presented here: Limanda limanda, Platichthys flesus and Solea solea.

In this study phytoplankton pigments and fatty acids were used as biomarkers to study trophic relationships between phytoplankton and zooplankton. These markers permit the characterization of both suspended matter and copepods, allowing examination of the transfers from food to zooplankton. A drogue study was carried out to follow a water mass in the coastal waters off the eastern English Channel over a 3-day period, with samples collected every 3 h. The study focused on the dominant calanoid copepod species: Temora longicornis, Acartia clausi and Pseudocalanus elongatus. Our study was performed during the spring phytoplankton bloom when solitary cells of Phaeocystis sp. formed 90% of the total phytoplankton. Fatty acid analyses provided an indication of the low nutritive value of these algal cells; in contrast to other algal species which had higher nutritional value (e.g. colony-forming diatoms, Cryptophytes and dinoflagellates). Our results suggest that all species selectively grazed on Phaeocystis sp. and non-selectively on diatoms. Dinoflagellates were avoided by all species. Temora longicornis selectively grazed on Cryptophytes, which may be related to the nutritional value of this algae. The fatty acid composition of the three copepod species indicated an herbivorous' diet for P.elongatus and an omnivorous one for A. clausi and T longicornis, which is less opportunist.