The occurrence of some metazoan parasites of Atlantic cod, Gadus morhua L., in relation to age and sex of the host in Balsfjord (70 degrees N), NorthNorway

Age and sex differences in the occurrence of some metazoan parasites were i nvestigated in 243 cod (Gadus morhua L.) from Balsfjord, a subarctic fjord in northern Norway. Thirteen species of parasite were studied. comprising s even nematodes, three parasitic copepods, one acanthocephalan, one cestode and one digenean. The nematode Anisakis simplex showed significant increase s in both prevalence and mean abundance with host age, while the digenean H emiurus levinseni showed a significant increase in mean abundance with age. The increases probably result from a long parasite life-span for A. simple x and changes in the feeding pattern of cod with age for H. levinseni. Prev alence of the nematode Contracaecum sp. and mean abundance of the acanthoce phalan Echinorhynchus gadi were significantly higher in male than in female cod, whereas mean abundance of H. levinseni was significantly higher in fe male cod. These results suggest that there may be differences in feeding be haviour between male and female cod in Balsfjord.