The discrimination of roach Rutilus rutilus (Linnaeus, 1758) populations in different parts of a river system. An investigation using biochemical markers

Roach populations from different parts of the network of the French Upper Rhone and from Lake Geneva were examined. Several populations were discriminated by the electrophoresis of 16 enzymes coded for by 28 gene loci. 90% of the overall genetic variation was due to intrapopulation variation. Some affinity was found between the populations of Lake Geneva and the Rhone immediately downstream, but the stocks of the Rhone farther down proved to be clearly distinct from these (genetic distance D = 0.048) and probably included several independently reproducing populations. One of these populations was only found in the channel, others inhabited a side arm (D between them = 0.035) or succeeded each other in it, presumably in connection with spawning migrations.