Observations sur le comportement migratoire des Aloses (Alosa alosa L.) dans le canal artificiel de l'usine de Golfech

Abstract

For 4 consecutive years, daily fishing over the period of upstream migration of alewives (Alosa alosa L.) were performed on the site of Golfech: an hydroelectric plant on the Garonne river. This paper presents observations on the migratory behaviour of this fish in the artificial canal located between the plant and the confluence.The migration develops in spring when the water temperature reaches approximately 16° C and, above this level, the maximal affluence of alewives corresponds with increasing temperature phases.The relationship between water temperature and capture abundance is significant if one consider the beginning of the migration, then becomes inconsistent when the migration reaches the maximum.Similar to the thermal factor, there are hydraulic characteristics which influence the alewive migration (water flow through the different turbines, downstream level…).The evaluation of the fish stock, using marking techni is not satisfactory because of the small number of fish recaptured.Analysis of daily fishing data demonstrates that there is no accumulation of alewives day after day, in front of the factory. © Masson, 1985.