Age and growth of Anguilla anguilla in the Camargue lagoons

Age and total length (LT) data from a 11 year monitoring of the Anguilla anguilla eel population of the Camargue lagoons (Rhoˆ ne delta, southern France) were collected for glass, yellow and silver eels. Three distinct models were calibrated to describe the growth process of undifferentiated eels, females and males, respectively. Uncertainty of parameter estimates was evaluated by bootstrap- ping. Females were characterized by larger asymptotic body size (LT) than males (580 50 v. 388 13 mm) and faster growth, whilst the Brody growth coefficient was larger for males than for females (means S.D. 300 103 168 103 v. 173 103 050 103). Sexual differentiation was estimated to begin at 204 38 mm mean S.D., i.e. at the end of the second year in the lagoons, well before the LT at which macroscopic differentiation became possible (c. 300 mm). Males probably leave the lagoon or die (due to either natural or fishing mortality) within the first 3 years, whilst females can remain up to 5 years. Sexual differentiation and maturation have a major role in shaping the LT structure of the population. The LT and mass (M) data were fitted by allometric curves M 1⁄4 aLTb. The calibration of distinct curves for data from different years indicated that the allometric coefficient a was subject to wider interannual fluctuations than the allometric exponent b. A negative correlation linked the average LT and the allometric exponent (r 1⁄4 058, P < 001).