Restauration de la Biodiversité : le cas des poissons migrateurs dans la Meuse.

During the 19th century amphibiotic anadromous migratory fish (sea lamprey Petromyzon marinus; river lamprey Lampetra fluviatilis; european sturgeon Acipenser studio; Atlantic salmon Salmo salar;sea trout Salmo trutta trutta; hooting Coregonus oxyrhinchus; allis shad Alosa alosa; twaide shad Alosa fallax) were widespread in the entire River Meuse basin, and commercial fisheries were prosperous in France, Belgium and the Netherlands. From 1800 onwards, the bulding of navigation weirs on the the River Meuse, the increase of industrial and urban water pollution, and the overexploitation of riverine fish stocks caused the regression and extinction of these migratory fish populations (the Atlantic salmon became extinct in the 1930's). The capture of several individuals of sea trout in 1983 in a small tributary the Meuse at the Belgian -Dutch border triggered the idea of attempting to restore an Atllantic salmon run in the Meuse river system. A "Meuse 2000 Project" started in 1987 as a contribution of Wallonia to the European Year of Environnement .A first facet of this program consisted in assessing the carrying capacity of nursery streams in the Belgian Ardennes by means of of experimental reintroduction stockings (with fish from Scottish, Irish and French origin) into selected salmonid streams in order to demonstrate the good ecological quality of these habitats. The second, most difficult and expensive facet of the program me focused on the restoration of fluvial connectivity and free circulation of upstream migrating adult fish. In 1998-2001, modern fish-passes have been built at three navigation weirs on the Belgian Meuse between the Belgian-Dutch border and Liege, complementing a series of new fishways constructed since 1989 at five of the seven weirs obstructing the Dutch Meuse. Since 2000 , the International Commission for the Protection of the Meuse has been coordinating actions towards restoring the free circulation (upstream and downstream) of Atlantic salmon and other amphibiotic species such as sea trout and European eel ( Anguilla anguilla) in the River Meuse basin including the French upper course. This communication reports on the long genesis, wide partnership, first successful results (92 new Meuse salmon recorded in the Dutch Meuse since 1994; 13 returning salmon caught in fish-passes in the Belgian Meuse at Lixhe and the Bewinne at Berneau in October 2002 -January 2003), and great future ecological prospects (recovery of other anadromous migratory fish) of an historical operation which has succeeded in re-estblishibg the presence of S. salar in the Belgian Meuse about seventy years after it became extinct.