Recrutement des civelles (Anguilla anguilla) sur la cote Mediterraneenne Française: Analyse comparee des caracteristiques biometriques et pigmentaires des saisons 1974-75 et 2000-01

Abstract

A sampling of glass eels, Anguilla anguilla, took place at the Fourcade sluice (Saintes-Maries-de-la-Mer, French Mediterranean coast) between November 2000 and May 2001. Glass eels were captured throughout the sampling period but abundance maxima occur in January-February and, to a lesser degree, in April. In order to optimise recruitment in the interior coastal lagoons, the suggested management measure would therefore be to open the sluice gates in mid-winter. The monitoring of monthly proportions of different pigmentation stages (from V A to VI A4) allows to conclude that there is a general aging of recruited glass eels from November to March followed by a second influx of young glass eels in April. At the same time, a clear reduction in mean monthly masses and lengths is observed even when considering a single pigmentation stage (V B). These results on the evolution of biometric and pigmentation characteristics support the conclusions of studies already carried out on the French Mediterranean coast (1930's and 1970's) as well as published data from different sites on the Atlantic coast. A comparative analysis of these data with those resulting from the most recent study on the French Mediterranean coast (Bages-Sigean, Languedoc-Roussillon, 1974-75, LECOMTE-FINIGER, 1976) shows a completely different monthly pigmentation composition and reveals a significative decline in the length of glass eels in the range of 5 % over 25 years.