Development of a fish-based index to assess the ecological quality of transitional waters: the case of French estuaries.

The Water Framework Directive requires the assessment of the ecological status of transitional waters considering the fish component. An original methodology, based on a pressure-impact approach, was established to develop a multimetric fish-based index to characterize the ecological quality of French estuaries. An index of contamination, based on the chemical pollution affecting aquatic systems, was used as a proxy of anthropogenic pressure. The fish metric selection was based on their response to disturbances tested via statistical models (generalized linear models) taking into account sampling strategy and estuarine features. Four metrics, for which discriminating responses to level of pressure were demonstrated, were retained to constitute the estuarine multimetric fish index. This new tool appeared particularly relevant to detect the contamination effects on fish communities in estuaries. It could help managers to take decisions in order to maintain or reach the good status required by the Water Framework Directive for 2015.

Contamination of fish from different areas of the river Seine (France) by organic (PCB and pesticides) and metallic (Cd, Cr, Cu, Fe, Mn, Pb and Zn) micropollutants.

Organochlorine and metal pollution were studied in fish from different sites of the river Seine situated upstream and downstream of Paris. The metal content in roach were similar to those usually found in freshwater fish species. The PCB and the Pb pollutant levels in the fish evolved similarly along the river: from 1300 to 16,000 micrograms/kg dry weight for the PCBs and from 0.3 to 9.5 mg/kg for Pb, while the content of other metals did not change. The stations with the highest organochlorine contents are situated downstream from the Parisian discharges where there is a reduction of fish species present from 31 to 18. Fish caught at one station situated downstream from an industrial area (Guernes) contained a higher proportion of tri- and tetrachlorobiphenyls than fish from the other stations. Their muscle contents are above the French Food Standard of 2 ppm for PCB in fresh muscle.