Parasites of herring (Clupea harengus L.) larvae from a local Norwegian fjord stock

A parasitological examination was performed on 2444 juvenile herring Clupea harengus (11-54 mm) trawled from Osterfjorden, west Norway in May 2000. Most (99.3%) were larvae (<40 mm), whereas 18 fish were at transition stage or metamorphosed. We found five endoparasite species: Lecithaster gibbosus (Digenea), a juvenile didymozoid (Digenea), tetraphyllidean and pseudophyllidean cestode larvae and Hysterothylacium aduncum (Nematoda) larvae. The only ectoparasite detected was a Caligus elongatus (Copepoda) chalimus larva. Lecithaster gibbosus, Hysterothylacium aduncum and Caligus elongatus larvae have previously been shown to kill cultured herring larvae by causing mechanical damage. The rarity of metazoan parasites in herring larvae from this locality suggests that these are not a significant cause of natural mortality in this area.