[Current state of fish parasites in lake Trasimeno. I. Observations on the Tinca tinca L. population].

An investigation was carried out to identify the actual state of parasitism in the Tinca tinca population of Trasimeno lake (Umbria, Italy). It has been found: a high number of infested specimens, eleven species of parasites, of which four were not yet known to be in the lake, frequency variations of certain species, the absence of others that in the past were present. The species of parasites observed are, in various ways, distributed in the Paleartic region. Some are considered to be of allochthonous origin. The organs most frequently involved were the gills and the ureters followed by the intestine and the liver.