Ecologie d'une population de vandoises, Leuciscus leuciscus (L.) dans la rivière Ourthe (Bassin de la meuse, Belgique)

Abstract

From samples of dace taken by electrofishing from 1971 to 1976, the chief features of the population have been described and analysed: age structure (maximum age was 15 years), variations in the abundance of the different year-classes for 1958-1972, annual mortality rate (M = 38%), growth rate in length (21 cm at 5 years for the two sexes combined), sex ratio (males/females = 1.04), age of sexual maturity (3-4 years and 16 cm), absolute individual fecundity as a function of size and age, seasonal cycle of the condition and development of the gonads, length-weight relationship, spawning period. The dynamics (growth in weight, survival, fecundity and somatic production) are summarised for a typical cohort. Estimates are made for the absolute population biomass (6.3 kg/ha), somatic production (2.3 kg/ha/year), potential reproduction (35 ovules/m2) and the exploitation of the fishery (2.0 kg/ha/year). The discussion reviews the demography of dace in several european rivers. © 1981 Masson.