Host and Seasonal Associations of Echinorhynchus salmonis (Acanthocephala: Echinorhynchidae) in Lake Michigan Fishes

Abstract

Echinorhynchus salmonis Müller was the dominant intestinal parasite infecting 14 species of southwestern Lake Michigan fishes. New host records are reported for chinook salmon, Oncorhynchus tshawytscha, and slimy sculpin, Cottus cognatus. Infections were heaviest in members of the Salmonidae. Host–parasite relationship in smelt was most closely analyzed. No pronounced seasonal periodicity in the rate and intensity of infection or worm maturation was observed. Recruitment and maturation occurred throughout the year but were, however, enhanced by colder and warmer temperatures, respectively. Sex ratio was nearest to even in winter. Fifty percent or more of worms were localized in the posterior-most region of host intestine and posterior migration with maturation was indicated. Heavier infections were noted in larger (older) fishes. Alternative routes of infection of the larger piscivorous salmonids via transfer hosts are suggested. Female hosts were more heavily infected than males. Echinorhynchus salmonis was not shown to seriously threaten its host's health or survival.