A partir de données morphologiques et de mesures de salinité, un modèle numérique de mélange des eaux dans l'estuaire du Bou Regreg a été élaboré. L'estuaire a été divisé en 23 tronçons d'un kilomètre de long pour lesquels le modèle permet de calculer l'évolution dans le temps des salinités moyennes à mi-marée. Au cours de la période étudiée, les échanges entre les 23 tronçons paraissent largement dominés par la dispersion. Le modèle reproduit correctement l'évolution de la salinité après une crue artificielle due à un lâcher de barrage mais également dans d'autres situations.

By-catch of 0-group flounder, Platichthys flesus L. 1758, in the Loire glass-eel fishery was estimated for 1987 and 1988. Samples were taken throughout the estuary but the by-catch mainly occurred in the Central area. This pattern was observed in both surveys despite different hydrological conditions. The overall by-catch was 41 million animals for 1987 and 7 million for 1988. This difference was not only a consequence of a lowered fishing effort, it also suggests a difference in year-class strength. Recause of the great variability of postlarval distribution the accuracy of the estimates was very poor and only orders of magnitude can be discussed.

A simple laboratory method for determining Benthal Oxygen Demand is described. Results of experiments carried outon the Castletown Estuary are given. The Benthal Demand Index is calculated for all stations in the Castletown Estuaryto determine the relative effect of Sediment Oxygen Demand from the anoxic muds and Biochemical Oxygen Demand fromorganic matter in suspension.