The helminths in the gut of perch (Perca fluviatilis L.) in a small oligotrophic lake in southern Norway.

A total of 311 perch were examined for gut parasites during the period from April 1972 to December 1973. Four different metazoan parasites were found; Proteocephalus percae (Müller, 1780), Bunodera luciopercae (Müller, 1776), Acanthocephalus lucii Müller, 1776 and Camallanus lacustris Zoega, 1776. B. luciopercae and P. percae exhibited similar seasonal cycles in appearance and abundance. They were both absent from the fish population during June/July. A. lucii and C. lacustris on the other hand had a peak in infection intensity and incidence during the summer and autumn months. From September/October one year to May/June the following year B. luciopercae was the dominating parasite species showing the highest incidence (approximately 95%) and intensity (a mean of about 25 parasites per infected fish). When 2 times 2 contingency tests were applied on the material from this period a significant negative correlation between the presence of P. percae and A. lucii could be pointed out while there was no correlation between the presence of any of the other 3 parasite species.