Population dynamics and interrelationships of some Dactylogyrus and Gyrodactylus species on Cyprinus carpio.

During 1986/87, 922 carps have been examined for ectoparasitic helminths. Altogether 6 species of Gyrodactylus and 4 species of Dactylogyrus were found. The most frequent parasite on the gills was D. extensus; it shows a great tolerance to the water temperature with two peaks of infestation between 2 and 9 degrees C. Additionally, relationships between the seasonal dynamics of the invasion cycle of D. extensus and D. anchoratus were recognized. In addition to Dactylogyrus 2 species of Gyrodactylus, G. shumani and G. sprostonae occurred on the gills. G. shulmani tends to show rapid population growth in the warmest months in summer. The highest number of helminths were found in the beginning of September. It is conceivable that G. shulmani will be an agent of a new helminthosis in the GDR. The infestation by G. shulmani is often accompanied by the occurrence of D. vastator. Both species reach the maximum values approximately at the same time. G. sprostonae reached high intensities already in June and August. The common infestation increased by G. katharineri, G. stankovici and G. kherulensis on skin nd fins. G. katharineri seems to have the most favourable conditions in April. The indices dropped to a minimum in summer and autumn. G. stankovici has likely similar ecological claims as G. katharineri and shows a peak of incidence in April, too.