ANALYSIS OF FISHING GEAR FISHERY STATISTICS IN THE RHONE RIVER BASIN .2. STUDY OF THE CATCH

From the data on fish captures in the Rhone and Saone rivers declared to the fishing authorities in 1988 and 1989, we assessed a harvest from fishing gear of 238 and 272 tons per year, respectively. The captures essentially consist of large cyprinids (Abramis brama, Blicca bjoerkna, Rutilus rutilus and Chondrostoma nasus), euryhaline fishes such as mullets (essentially Liza ramada) and eels (Anguilla anguilla). Commercial (professional) fishing represents on average 72% of the captures. For certain species such as shad (essentially Alosa fallax), pike(Esox lucius), pikeperch (Stizostedion lucioperca) and catfish (Ictalurus melas), recreational fishermen (amateurs) catch quantities similar to the professionals. Moreover, they account for the majority of the yield of the upper Saone. The biomass of the captures in the deltaic Rhone is ranked second behind that of the lower Saone, situated in the center of the basin. This sector is a region of national importance for a strictly fluvial fishery. The declared captures follow a seasonal cycle related to fishing effort as explained in the first part of the paper (CHANGEUX et ZYLBERBLAT, this issue). The shads are captured when the other fisheries are closed in the month of May. The mullets are captured during the ''cold'' season and the small cyprinids (essentially Alburnus alburnus) are caught during the ''warm'' season. In the lower Saone, the analysis of the Catch Per Unit Effort (CPUE) shows significant variations between the categories of fishing as described in the first part of the paper. The use of CPUE is suggested in monitoring the stocks of the most important catches of the sector.