Reproductive output and population biology of Cystidicola stigmatura (Leidy) (Nematoda) in Arctic char, Salvelinus alpinus (L.) (Salmonidae)

Abstract

The reproductive output and population biology of the swim bladder nematode, Cystidicola stigmatura, were examined in Salvelinus alpinus in Gavia Lake, Northwest Territories, Canada. The size and number of gravid female nematodes increased with fish age, supporting the suggestion that worms are long-lived and grow throughout their lives. Fecundity was linearly related to the length of gravid female nematodes. Reproductive output of parasites in individual fish (estimated by the number of free eggs in swim bladders) was overdispersed in the host population and was concentrated in the oldest age-classes of char. The latter feature makes populations of the parasite susceptible to exploitation of their fish hosts. It was estimated that in Gavia Lake exploitation of larger fish decreased nematode egg production by about one half over a 7-year period. Decline of fish stocks has probably resulted in extinction of populations of C. stigmatura in at least nine lakes in southern Ontario and northern New York State.