L'état des communautés exploitées au large des côtes de France. Application d'indicateurs à l'évaluation de l'impact de la pêche.

Since about twenty years, Ifremer have carried out fishery surveys along the French coasts. A dynamic indicator-based approach to the assessment of multi-stock fisheries has been applied to these data series. Reference points for non-commercial populations and community indicators are seldom available, but reference directions are well established: it is known whether fishing will increase or decrease the indicator, hence the direction that should be avoided. A set of simple indicators of fishing impacts on fish populations and communities were estimated from time-series data provided by scientific surveys (population abundance and average length, community total biomass and number, average length and weight, and size spectrum). Trends in these indicators were assessed within a hypothesis testing framework. The result of the assessments was a table where desirable trends were scored “green” and undesirable trends were scored “red” to draw attention on the changes in the fish community. The method is demonstrated for several coastal and shelf sea communities monitored by French surveys. The Gulf of Lions and the Celtic Sea were found to be the communities most impacted by fishing, whereas climate changes seem to be responsible for changes in the East-Atlantic ecosystems. In the English Channel and the North Sea, the calculated indices are very sensitive to recruitment variations.