The Prevalence, Abundance, and Density of Pseudoterranova sp. (p) Larvae in the Flesh of Cod (Gadus morhua) Relative to Proximity of Grey Seal (Halichoerus grypus) Colonies on the Coast off Drangar, Northwest Iceland

Abstract

About 300 cod (Gadus morhua) were sampled on three different sites of different proximity to grey seals (Halichoerus grypus), which are the most important final host for Pseudoterranova krabbei, off Drangar, Northwest Iceland, in the summer of 2004. Cod caught at each station were grouped into four sizes: (1) 40–54 cm, (2) 55–59 cm, (3) 60–69 cm and, (4) >70 cm. Difference in prevalence between catch-sites were analyzed by a binary logistic regression model. Abundance, and density were investigated with multiple regressions. As expected prevalence, abundance and density of Pseudoterranova larvae were highest in the fish caught closest to shore, which was also in closest proximity to grey seal colonies and in the shallowest waters. In the closest proximity to grey seal colonies and in the shallowest water, the prevalence and abundance of sealworm larvae increased with increased length of fish. Finally, the density of Pseudoterranova larvae in cod declined exponentially with depth: 50% at 65 meters and almost zero at 210 meters. In the paper these observations were discussed in relation to sealworm eggs dispersal, depth gradient off the coast, temperature tolerance of the sealworm ovum, and behavioral types of Icelandic cod.