Landlocked Arctic charr ( Salvelinus alpinus ) population structure and lake morphometry in Greenland - is there a connection?

Abstract

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 km 2 , maximum depth 200 m). Arctic charr were found in one to three diAerent 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 20 m and a surface area 20 m, large-sized charr were more abundant, and the length-frequency distribution of the population was bi- modal, with a first 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 significantly positively correlated with lake maximum depth and volume, and the mean size of large-sized charr was significantly 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 influenced by lake-water transparency and the presence or absence of three-spined stickleback (Gasterosteus aculeatus).