SPATIAL RELATIONS BETWEEN LACUSTRINE ICHTHYOFAUNA AND A PREDEFINED PARTITION OF THE LACUSTRINE BASIN

In order to study the spatial organization of the ichtyofauna of homogeneous lakes, several seasonal fishing campaigns have been carried out in two lakes of the Jura using vertical roller gill nets. This technique, which prospects the entire depth of water wherever it is disposed, allows to make a rigourous sampling strategy by dividing the plan of the lake according to pre-defined topogaphic descriptors considered as poles which creat a differential attraction on the different species of fishes. For each sampling campaign, the simultaneous prospection of all the different attraction poles have been repeated six times. Global, then inter and intra-group correspondence analysis have been made on every seasonal series of catches per unit effort grouped by pole in order to estimate spatial variability, and by sampling sequences in order to analyse the temporal variability. This approach shows a strong logic organization of species around the posts prospected and the dynamic aspect of the attraction of the pre-defined poles.