Fecundity of sealworm (Pseudoterranova decipiens) infecting grey seals (Halichoerus grypus) in the Gulf of St. Lawrence, Canada: lack of density-dependent effects.

Uterine egg counts were determined by means of an electronic particle counter in individual female sealworm, Pseudoterranova decipiens (Nematoda: Ascaridoidea: Anisakidae) collected from grey seals (Halichoerus grypus) from Anticosti Island, northern Gulf of St. Lawrence, in August and September 1992. Mean number of eggs per female was 54,916.9 (+/- 51,866.4), with a maximum of 300,000. Egg counts were strongly correlated with worm length, and less so with host sex and age, sealworm sex ratio, and densities of Anisakis simplex and Phocascaris sp. No effect of sealworm density on worm egg counts was determined and competitive effects by Contracaecum osculatum on sealworm fecundity were not observed. Analyses demonstrated that variation in sealworm fecundity was greater among seal hosts within groups than between groups for host age and sex, density of sealworm, and density of C. osculatum. No evidence for density-dependent regulation of sealworm fecundity could be found. Variations in worm egg counts are attributed to individual host effects on worm growth and fecundity.