INFECTION OF SALMINCOLA-EDWARDSII (COPEPODA, LERNAEOPODIDAE) IN AN AGE-STRUCTURED POPULATION OF ARCTIC CHARR - A LONG-TERM STUDY

The parasite-host relationships between Salmincola edwardsii (Copepoda : Lernaeopodidae) and Arctic charr Salvelinus alpinus were studied in lake Takvatn, northern Norway, over an 8-year period. The infection le vels were modest, with an overall prevalence of 16.1% and an abundance of 0.5 parasites fish(-1). Most of the infected fish (54.1%) had only one parasite attached, whilst only 43% had more than 10. In general, parasite infection increased with increasing age, and hence size of th e fish. The increase was modest up to age 7, whereafter a steep increm ent in parasite burdens occurred. Within each age class there was litt le effect of either fish size, gender, maturation or choice of macroha bitat upon parasite abundance. There was also little year-to-year vari ation in infection of the different age classes, indicating a high deg ree of stability of the parasite-host interactions in this system. The infection levels exhibited seasonal changes, being lowest in early su mmer and highest during winter. The infection rates seemed to be relat ed to seasonal and ontogenetic habitat shifts of the charr. (C) 1997 T he Fisheries Society of the British Isles.