Anisakid (Nematoda) infestations in Icelandic grey seals (Halichoerus grypus Fabr.)

Abstract

Anisakid nematode infestations in stomachs of 196 grey seals from Icleandic waters were examined during the period 1989-93, and Pseudoterranova decipiens s.l., Contracaecum osculatum s.l., Phocascaris cystophorae and Anisakis simplex s.l. were found in seals from all areas and seasons. No difference in nematode abundance was observed between the sexes of grey seal but the number of worms increased with the weight of the seals. Abundance of P. decipiens and C. osculatum showed geographical and seasonal differences. Seals from the Breidafjord and Faxafloi areas had greatest abundance of P. decipiens with an increasing trend from spring to autumn, reaching the highest levels during period of reduced feeding in the breeding season in October to December. Abundance of C. osculatum was greatest in seals from the Breidafjord area and decreased from spring to autumn. The abundance was low in seals from the Faxafloi area and remained unchanged from spring to autumn. Most samples from the south coast were collected from August to December and showed low and declining abundance of all anisakid species during the breeding season. No indications of changes in P. decipiens abundance were observed in grey seals from West Iceland between 1979-82 and 1989-93. Proportions of adult P. decipiens and C. osculatum showed a decreasing trend when abundance of each species in the seal stomachs was increasing.