Les structures d'un grand cours d'eau à Salmonidés: La Loue (massif du Jura) essai typologique et problèmes des relations entre espèces et milieu

Abstract

Typological studies have been done on a large salmonid river in Jura mountain (the river Loue), by means of a factor analysis.This method is used for the analysis of longitudinal variations of 18 physical and chemical properties and for studying the distribution of 135 fresh-water species: Fish (18 species), Plecoptera (27 species), Ephemeroptera (33 species) and Trichoptera (57 species), located on 18 stations distributed all along the river (126 km).The biological "structures" are determined separately for each order, then for all the fauna: 4 groups and 12 sub-groups of "ecological affinities" are established.The analysis of the abiotic environment indicates a hierarchical participation of the components but also the absence of a clear abiotic "structure" which conforms to the theory of the "équivalent ecological combinations" and emphasises the integral nature of the species.The results obtained at the species level, from the water course, and from the physical and chemical components are discussed and compared. The value of the typological research is pointed out together with the relative character of the causation of the species and their groupings. © 1974 Masson.