The relationship between the size of some salmonid fishes and the intensity of their acanthocephalan infections.

In Lake Michigan, abundance of c8000 worms, mostly Echinorhynchus salmonis, was independent of the age (weight) of coho salmon Oncorhynchus kisutch, chinook salmon. O. tshawytscha and lake trout Salvelinus namaycush. Other E. salmonis infection patterns include steady increase in abundance with host age and a maximal increase in mid-age. A decrease in abundance with host age was demonstrated in other acanthocephalan species. Such patterns were primarily related to host feeding behavior as well as spatial and seasonal distribution of invertebrate and vertebrate larval hosts. A progressive increase in the abundance of Echinorhynchus through mid-age or through life is associated with a stable intake of an invertebrate diet, including the infected intermediate host, in larger volumes by older fish. -from Author