The Prevalence, Abundance, and Density ofPseudoterranovasp. (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

Erlingur Hauksson

doi:10.1155/2011/235832

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 forPseudoterranova 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 ofPseudoterranovalarvae 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 ofPseudoterranovalarvae 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.

Highlights

Nematode infestation of cod (Gadus morhua) causes losses to fisherman and to fish merchants alike and, in consequence, necessitated special precautions, which may add considerably to the production or processing costs [1]
Abundance and density of Pseudoterranova larvae were highest in the fish caught closest to shore, which was in closest proximity to grey seal colonies and in the shallowest waters
The life cycle of Pseudoterranova krabbei is similar to the life cycle of P. decipiens, which has been described by McClelland et al [12]

Summary

Introduction

Nematode infestation of cod (Gadus morhua) causes losses to fisherman and to fish merchants alike and, in consequence, necessitated special precautions, which may add considerably to the production or processing costs [1]. Grey seal (Halichoerus grypus) is considered to be the most important final host for Pseudoterranova krabbei and common seals (Phoca vitulina) for P. decipiens sensu stricto [4]. In Icelandic waters grey seal is recognized as the main final host for Pseudoterranova larvae and common seals are believed to contribute not as much, as the grey seal, to the infestation of cod and other commercially important fish [5, 6]. The life cycle of Pseudoterranova krabbei is similar to the life cycle of P. decipiens, which has been described by McClelland et al [12]

Methods

Results

Conclusion