An investigation into the metazoan parasites of the spiny dogfish (Squalus acanthias L.), off the west coast of Ireland

The present study was undertaken to examine the parasite fauna of spiny dogfish, and to determine seasonal variations in infection rates and faunal composition. A total of 10 metazoan parasite species was recorded, of which four species occurred in the intestine, three species were parasitic on the gills, two species occurred on the skin, and one species parasitized the spiracle. However, a cumulative parasite species richness curve indicated that a larger sample may have yielded additional parasite species. The parasite assemblage consisted of five species of copepods (Eudactylina acanthii Scott, Caligus curtis Müller, Pandarus bicolor Leach, Echthrogaleus coleoptratus (Guerin-Meneville) and Pseudocharopinus bicaudatus (Krøyer)), two species of nematodes (Anisakis simplex Rudolphi and Hysterothylacium aduncum (Rudolphi)), two species of cestodes (Trilocularia gracilis Olssen and Gilguina squali (Fabricius)), and one species of monogenean (Erpocotyle abbreviata (Olssen)). The parasite fauna was found to be similar to that of S. acanthias from the North Sea, and from New Zealand waters. Results obtained during the present study indicate that the infection rates of certain parasite species display seasonal cycles, most species displaying their greatest prevalence in spring and their lowest prevalence in autumn.