EFFECTS OF ACIDIFICATION ON NORMAL AND DWARF ARCTIC CHARR SALVELINUS-ALPINUS (L) IN A NORWEGIAN LAKE

We investigated the effects of acidification on two morphs of Arctic c harr Salvelinus alpinus in Lake Sirdalsvatn, southwestern Norway. Thes e morphs, dwarf and normal charr, differed in body size and morphology , age at maturity, and habitat use during feeding and spawning. The se gregation during spawning appeared to be almost complete, corroboratin g the results of a preview enzyme electrophoretic study (Hindar et al. , 1986 Biol. J. Linn. Soc., 27, 269-85) which suggested that the two c han morphs represent sympatric populations with a restricted amount of gene flow between them. Both morphs showed a positive correlation bet ween year-class strength and minimum pH in spring/summer of that year, hence both morphs appeared to be affected by acidification. If is sug gested that addition of limestone to the spawning substrate used by ch arr may be one way to protect the unique genetic and ecological variab ility of Arctic charr in this lake.