Genetic basis of life history variations among sympatric morphs of Arctic char Salvelinus alpinus

Four morphs of arctic char, Salvelinus alpinus, which differ substantially in morphology, behaviour, and life-history characteristics, occupy different habitats in the landlocked lake Thingvallavatn, Iceland. Progeny of wild morphs reared in a common environment showed early size differences among morphs that were maintained throughout the 3-year experiment. Large benthivorous and piscivorous char progeny became larger on average than planktivorous and small benthivorous char progeny. Progeny of large benthivorous char had the highest specific growth rates whereas progeny of small benthivores tended to grow the slowest. Some male progeny of small benthivorous and planktivorous char (11 and 23%, respectively) became sexually mature 2 years after fertilization. In year 3 the majority of fish (both sexes) in both progeny groups (70 and 85%, respectively) became sexually mature, and a small proportion (14%) of male piscivorous char progeny became sexually mature. No sexual maturation was recorded in large benthivorous char progeny. We conclude that life-history differences among the morphs are partly genetically based.