Effects of acidification on normal and dwarf Arctic charr Salvelinus alpinus (L.) in a Norwegian lake Original Research Article

We investigated the effects of acidification on two morphs of Arctic charr Salvelinus alpinus in Lake Sirdalsvatn, southwestern Norway. These morphs, dwarf and normal charr, differed in body size and morphology, age at maturity, and habitat use during feeding and spawning. The segregation during spawning appeared to be almost complete, corroborating the results of a previous enzyme electrophoretic study (Hindar et al., 1986 Biol. J. Linn. Soc., 27, 269-85) which suggested that the two charr morphs represent sympatric populations with a restricted amount of gene flow between them. Both morphs showed a positive correlation between year-class strength and minimum pH in spring/summer of that year; hence both morphs appeared to be affected by acidification. It is suggested that addition of limestone to the spawning substrate used by charr may be one way to protect the unique genetic and ecological variability of Arctic charr in this lake.