Habitat use of arctic charr Salvelinus alpinus in Thingvallavatn, Iceland

Habitat use by four morphs of arctic charr Salvelinus alpinus , was investigated in Thingvallavatn, Iceland, by sampling with pelagic and benthic gill nets. The habitat use by different morphs is as may be expected from their morphology and diets. Within the population of PL-charr, young and small fish are more abundant on the bottom than in the pelagic zone, and there is a surplus of females in the pelagic zone. Along the benthic profile, young, small and immature PL-charr are more abundant in deep than in shallow waters. The results are discussed in relation to food supply, competition and predation. Possible reasons for the occurrence of four arctic charr morphs are also discussed.