Description d'une frayère et comportement de reproduction de la grande Alose (Alosa alosa L.) dans le cours supérieur de la Loire

Abstract

A spawning ground of Allis Shad (Alosa alosa L.) was described in the upper R. Loire and the reproductive behaviour was observed during the course of spawning season in 1988. The spawning ground was characterized by the présence of a groyne and by the abundance of fine materials in the substrate (sand an gravel). Reproduction was mainly nocturnal with a stronger intensity at mid-night. The spawning activity was correlated negatively with the daily flow rate and was not influenced by water température. The number of adults was estimated to about 34.200 individuals. Results showed that this spawning ground could be a campelled spawning ground, not typical for Allis Shad, and was one of the most important observed in large French streams.