Report on the programmes for migratory fish throughout the Garonne and Dordogne basins.

The Garonne and Dordogne basins cover an area of about 83,000 square kilometres. As in most of Europe's hydrographic systems, a sharp drop in these fish populations has been noted over the past century. The principal causes have been conflicting management needs, industrial use of the water courses, the appearance of urban and industrial pollution, and, in certain cases, over-fishing. In 1978, at the prompting of the Environment Ministry, the first co-ordinated operations for the restoration of migratory fish got under way in the Garonne and Dordogne basins with a << Salmon Plan >>. At that period, seven of the eight large migratory species were still present : the European sturgeon (Acipenser sturio), allis shad (Alosa alosa), twaite shad (Alosa fallax), the common eel (Anguilla anguilla), the river lamprey (Lampetra fluviatilis), sea lamprey (Petromyzon marinus) and the sea trout (Salmo trutta). Only the Atlantic salmon (Salmo salar) had completely disappeared. In 1999, an evaluation of the main features of the restoration plans revealed the following improvements. On the statutory plane, protection of part of their spawning habitats had been assured for several species, and fishing for three threatened species (sturgeon, salmon and sea trout) had been banned. On the water management plane, freedom of passage had been re-established over large stretches of the Rivers Dordogne, Vezere, Garonne, Ariege, Tarn and Aveyron, thus giving migratory fish access to the breeding grounds in the upper waters. On the biological plane, efforts to restore Atlantic salmon stocks had begun, with structural and organisational backing which held out hope of full re-establishment in the long term (including a reconditioning centre and fish farms). As for keeping check on the populations, control points had been set up at several strategic sites within the river basins, providing information about their colonisation. The first population figures had demonstrated a progressive installation of salmonidae in both the Garonne and Dordogne axes. However, the tracks kept on the migratory fish leave certain important questions open as regards evaluation of the stocks and the data are still insufficient to appraise the dynamics of each individual population.