A survey of the parasites of walleye pollock (Theragra chalcogramma) from the northeastern Pacific Ocean off Canada and a zoogeographical analysis of the parasite fauna of this fish throughout its range

Abstract

The results of a survey of the parasite fauna of walleye pollock (Theragra chalcogramma) collected off British Columbia during September 1978 to September 1979 are presented. Forty-three species of parasites (5 Protozoa, 2 Monogenea, 12 Digenea, 9 Cestoda, 6 Nematoda, 4 Acanthocephala, 4 Copepoda, and 1 Isopoda) are reported from examination of 312 pollock. Among these are eight species previously unreported from pollock (Zschokkella hildae Auerbach, 1910; Entobdella pugetensis Robinson, 1961; Copiatestes filiferus (Leuckart in Sars. 1885); Lecithophyllum botryophorum (Olsson, 1868); Prosorhynchoides basargini (Layman, 1930) metacercaria; Bolbosoma caenoforme (Heitz, 1920); Lepeophtheirus paulus Cressey, 1969; and Rocinela belliceps (Stimpson, 1864)). Analysis of the abundances, geographical distributions, and host specificities of the 65 parasite species reported from walleye pollock throughout its range reveals a preponderance of helminths, among them many larval forms, which are ubiquitous to marine fishes throughout much of the North Pacific basin. The parasite fauna of pollock is also characterized by a paucity of host-specific forms and by the occurrence of a large number of incidental species, a reflection of the broad feeding habits of this pelagic fish.