| Summary: | Arctic charr, fish, population structure Landlocked Arctic charr (Salvelinus alpinus) populations in sub-Arctic and Arctic Greenland lakes were sampled with multi-mesh-sized survey gillnets. The study covered a range of small shallow lakes (0.01 km2, maximum depth <3.3 m) to large deep lakes (43 km2, maximum depth >200 m). Arctic charr were found in one to three di€erent forms in lakes with maximum depths >3 m. A dwarf form occurred in all lakes in- habited by Arctic charr and was the only form in lakes with maximum depths <8 m. In deeper lakes with maximum depths >20 m and a surface area <0.5 km2, larger charr were found, although in low numbers, the length-frequency distribution being unimodal with a tail towards large sizes. In lakes with a maximum depth >20 m, large-sized charr were more abundant, and the length-frequency distribution of the population was bi- modal, with a ®rst mode around 10±12 cm and a second mode around 26±37 cm. In a single large and deep lake, a distinct medium-sized pelagic zooplankton-eating charr form occurred. Maximum size of individual charr was signi®cantly positively correlated with lake maximum depth and volume, and the mean size of large-sized charr was signi®cantly positively correlated with lake volume. Our study indicates that the charr population structure became more complex with increasing lake size. More- over, the population structure seemed to be in¯uenced by lake-water transparency and the presence or absence of three-spined stickleback (Gasterosteus aculeatus).
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