Which sturgeon species should be reintroduce in the Rhône River ?

Sturgeons were common in Western Europe until the 19th century, spawning in every important river from the Baltic Sea to the Black Sea. A population of sturgeons was present in the Rhone River (southern France) until the 1970’s. This population disappeared without having been characterized genetically. Two species were present in western Mediterranean: Acipenser sturio, ubiquitous along European coasts, and Acipenser naccarii, in Adriatic Sea and western Mediterranean; so the question of their sympatry in the Rhône River remains open. Nowadays, only one population of A. sturio remains in the Gironde estuary and two populations of A. naccarii in the Po (Italy) and Buna (Albany) basins. We studied archaeological remains from the Rhône River bank (Jardin d’Hiver), near Arles (France), where around 2 500 sturgeons bones, dated from the 2nd to the 6th century BC, have been excavated. It represents a unique opportunity to study a Mediterranean population of sturgeons long before its decline. Morphometric studies have already been carried out on these remains and only the species A. sturio has been identified (Desse-Berset, 1994). We completed this first investigation by genetics analyses on some archaeological bones, which allowed to confirm the presence of A. sturio in the Rhône River some 2500 years ago (Pagès, 2008). A larger study on archaeological remains is now undertaken to confirm the absence of A. naccarii in the Rhône River. Museum specimens from the Rhône River, which are not older than 200 years old, are also under analysis. Our aim is to compare the genetic diversity of the Rhône River sturgeon population through time, in order to estimate the impact of human activities. Data acquired will be useful for conservation efforts and particularly for a possible reintroduction of sturgeons in the Rhone River.