On the occurrence and morphology of Gyrodactylus pterygialis from saithe Pollachius virens in a Norwegian fjord.

A total of 308 Pollachius virens from a fjord near Bergen, western Norway, were examined for Gyrodactylus pterygialis over a 14-mo period; G. pterygialis showed the highest prevalence and density in winter/spring (November, January, March, and April pooled) but was absent in some months (August, September, and November). The morphology of the opisthaptoral hard parts of G. pterygialis were studied throughout the survey, and their variation is discussed with respect to host species, host locality, and different temperatures. On the basis of the present and previous descriptions, it is suggested that G. pterygialis is a parasite infecting gadine fishes of the genera Pollachius and Gadus, and that records from Pacific Eleginus and White Sea herring are distinct from G. pterygialis sensu Bychowsky and Poljansky, 1953.