LES FRAYÈRES POTENTIELLES DE L’ESTURGEON EUROPÉEN ACIPENSER STURIO L. 1758 DANS LE BASSIN GARONNE-DORDOGNE. MÉTHODES D’INVESTIGATION, ÉTAT ACTUEL ET PERSPECTIVES.

Abstract

Within the framework of the programme of restoration of the European sturgeon Acipenser sturio L. 1758, we listed and characterized the whole of the potential spawning grounds of this species in the Garonne and Dordogne rivers. The objective of this work was to carry out a first assessment on the current status of these zones and to evaluate their possible use as spawning ground. Before this work, the only available data consisted of a list of spawning grounds and spawner fishing zones indexed in 1952 and 1980 by investigations of the fishermen. An analysis of the data published on the other species of sturgeons made possible to determine the main physical characteristics of a spawning ground of sturgeons. By crossing information resulting from these 2 sources, historical and bibliographical, we retained a list of sites which were characterized at the time of field campaigns. This characterization related to bathymetry, current speed, nature of the substrate, position in the landscape and immediate anthropic impacts.The results of this study showed that the majority of the 28 studied sites met the characteristics of a spawning ground of sturgeons in term of current, depth and substrate. They could thus be regarded as potential spawning grounds, and their yield capacity potential was sufficient in the mid-term. Nevertheless, it appears necessary to protect the whole sites according to the regulations in order to withdraw them from the negative impacts of anthropic activity. / Dans le cadre du programme de restauration de l'esturgeon europÈen Acipenser sturio L. 1758, nous avons recensÈ et caractÈrisÈ l'ensemble des frayËres potentielles de cette espËce sur les fleuves Garonne et Dordogne. L'objectif de ce travail Ètait de rÈaliser un premier bilan sur l'Ètat actuel de ces zones et d'Èvaluer leur possible utilisation comme frayËre. Les rÈsultats de cette Ètude ont montrÈ que la majoritÈ des 28 sites ÈtudiÈs rÈpondait aux caractÈristiques d'une frayËre d'esturgeon en terme de courant, profondeur et substrat. Ils pouvaient donc Ítre considÈrÈs comme frayËres potentielles et leur capacitÈ d'accueil Ètait suffisante ‡ moyen terme. NÈanmoins il apparaÓt nÈcessaire de protÈger rÈglementairement l'ensemble de ces sites afin de les soustraire aux impacts nÈgatifs d'activitÈ anthropiques.