Anisakid nematodes in the common seal (Phoca vitulinaL.) in icelandic waters

Abstract

The occurrence of anisakid nematodes in the common seal in Icelandic waters was studied by investigating digestive tracts of 95 seals during 1979-82. The most abundant adult species was Pseudoterranova decipiens. Contracaecum osculatum, and Phocascaris cystophorae were less frequent. In addition larvae of Anisakis simplex were common. The prevalence and abundance of these nematode species did not differ significantly between seasons. The prevalence and abundance of P. decipiens showed marked geographic variations, with higher frequency and higher numbers in common seals from the west and northwestern coast, than from other coastal areas of Iceland. Male common seals had higher abundance of P. decipiens than females, and the number of P. decipiens worms was positively correlated with age in male seals. The sex ratios of P. decipiens and C. osculatum worms were close to 1: 1, but the sex ratio of P. cystophorae was close to 1: 1.7, in favour of females. A significant positive correlation was observed between numbers of P. decipiens and C. osculatum.