The objective of this study is to understand the influence on larval transport of the different hydrodynamic factors present in the English Channel. A population of annelid polychaetes, Pectinaria koreni, and a site, the Seine Bay, were chosen as being particularly appropriate for such a study. Different patterns of larval transport were observed during an intensive sampling season in 1987. The first pattern corresponds to the average residual transport which is dominated by tide: larvae are mainly transported northward. and a larval retention exists near the mouth of the estuary due to the interaction between the vertical current structure and the vertical distribution of larvae. The other patterns are wind-driven. Larvae are transported northward with westerly winds, without retention near the estuary. With easterly winds, larvae are transported westward, with or without retention. The speed with which the larvae are transported varies also with the wind direction: easterly winds cause a faster transport of larvae. In conclusion, even though tides are very important in the English Channel, most the variability in larval transport is probably due to the winds.