Ascaridoid Nematodes from the Stomach of Harp Seals, Phoca groenlandica, from Newfoundland and Labrador

Abstract

Stomachs of 488 harp seals, Phoca groenlandica, collected off Newfoundland and Labrador during 1984–88, contained four species of ascaridoid nematodes. Seals had high prevalences and abundances of Contracaecum osculatum B and Phocascaris sp. but were rarely infected with Anisakis simplex B or Pseudoterranova decipiens B (sealworm). Nematode abundance increased with age, and distribution of each species among seals was highly aggregated. Gastric lesions, often associated with clusters of nematodes, occurred in 13.8% of 405 seals. Female seals with large numbers of nematodes had a higher body condition index (sculp weight) than lightly infected females. Overall sex ratios of C. osculatum B and Phocascaris sp. were biased toward females, but sex ratios of adult nematodes among individual seals were heterogeneous. Most nematodes recovered were third- or fourth-stage larvae; adults of C. osculatum B and Phocascaris sp. were also common, but no mature females of A. simplex B or P. decipiens B were found. Harp seals are probably unimportant in the transmission of A. simplex but may be partly responsible for sealworm found in fish stocks off Newfoundland and Labrador. More information on other pinniped species is needed to assess more precisely the relative importance of harp seals in sealworm transmission.