Some remarks on the ecology of Echinorhynchus salmonis Muller 1784

The acanthocephalan Echinorhynchus salmonis showed a marked seasonality of occurrence in the yellow perch Perca fluviatilis in the Bay of Quinte, Lake Ontario. The incidence of the parasite started increasing in autumn and reached a peak in late winter. It started decreasing in March and fell to zero in August or September. Such seasonality has been previously observed for acanthocephalans in bodies of water which freeze, as does the Bay of Quinte. There is a single egg maturation period for the parasite in early summer, after which the parasites die. Infestation of intermediate hosts occurs in spring when the population of the hosts is high. The subsequent warm period ensures rapid development of the parasite. Within the fish the parasite is less affected by the lower temperatures prevailing in winter. No influence was apparent between the maturity and seasonality of the parasite and the food and breeding cycle of the fish.