Parasites of fingerling herring Clupea harengus L.: ecology and fine morphology

The parasite fauna of young-of-the-year herring Clupea harengus L., off Gullmarsfjord and Brofjorden, west coast of Sweden, was studied between May and October for 4 years, from 1994 to 1997. Fifteen species of parasites were found: two Protozoa - Trichodina sp. and Ceratomyxa auerbachi; one species of uncertain affinity - Ichthyophonus hoferi; two Monogenea - Gyrodactylus harengi and Pseudanthocotyloides heterocotyle; five Digenea - Cryptocotyle lingua metacercariae, Cercaria pythionike metacercariae, Hemiurus luehei, Lecithaster confusus and Pseudobacciger harengulae; three Cestoda plerocercoids - Bothriocephalus sp., an acrobothriid and a tetraphyllid; one Nematoda - Hysterothylacium aduncum larva; and one Copepoda - Caligus elongatus. The number of species found in this study represents more than one-sixth of all parasites reported in herring worldwide and all parasites were acquired locally. The parasite fauna of herring from the west coast of Sweden is compared with that of herring from the Baltic Sea and other areas of the north-east Atlantic. The prevalence and intensity of parasites are presented and discussed. Morphological descriptions are based on both light and scanning electron microscopy and new features are described. Possible applications of this new information about the parasite fauna, in different areas of fisheries and fish biology studies, are discussed.