La dévalaison des alevins de truite commune Salmo trutta L. I. Caractérisation en milieu artificiel

Abstract

A population of 500 brown trout alevins, Salmo trutta L., introduced in an artificial stream, and downstream migrants were isolated by successive trapping and fin clipped. The latter were then introduced in other artificial streams without fry and their behaviour was observed.As in nature, fry moved downstream during the night, some of them for a longer period than others. However, all surviving downstream migrants ended by taking up static swimming behaviour during the day and setting up a territorial mosaïc. But they did it later than non-migrants settfled in the first artificial stream. Downstream migrants were smaller than non-migrants at the end of the experiment. Their la te swimming and territorial behaviours and their weaker growth strengthened the hypothesis that downstream migrants undergo delayed development when compared to non-migrants. © 1980 Masson.