FREQUENCY-DISTRIBUTIONS OF FISH PARASITES IN THE PERCH PERCA-FLUVIATILIS L FROM LAKE CONSTANCE

Seventy perch (Perca fluviatilis) caught in Lake Constance at Langenar gen in May 1990 were examined for parasites. The frequency distributio ns of the eyefluke Diplostomum spathaceum (Rudolphi, 1819), and the ta peworms Proteocephalus percae (Muller, 1780) and Triaenophorus nodulos us (Pallas, 1781) fitted closely to a negative binomial. Only a few fi sh were highly parasitized. These fishes are devoured by the final hos ts: gulls (Diplostomum spathaceum) or the pike (Triaenophorus nodulosu s). The fish population was influenced negligibly and the parasite pop ulation stayed at a moderate level. During the spawning period female perch were infested with Proteocephalus percae more than the males. Th is may be because the females had a higher food consumption and became more infected by copepods (intermediate hosts). In contrast, Diplosto mum spathaceum, Ichthyocotylurus variegatus, Triaenophorus nodulosus, and Tylodelphys clavata did not occur in different numbers in female a nd male perches. The frequency distribution of Ichthyocotylurus varieg atus (Creplin, 1825) and Tylodelphys clavata (Nordmann, 1832) did not conform to a negative binomial.