Habitat and food choice of Arctic charr in Linnevatn on Spitsbergen, Svalbard: the first year-round investigation in a High Arctic lake

Habitat and diet of Arctic charr Salvelinus alpinus (L.) were studied by monthly sampling from late autumn to early summer in Linnevatn, Svalbard (78 degrees 3'N, 13 degrees 50'E). This is the first year-round study of a population of charr in the High Arctic, with samples being taken every 5-7 weeks. The ice cover lasted for more than 9 months, from mid-October to late July, with the greatest thickness in mid-May. Although most charr occupied the littoral zone during winter, the highest densities in April and October were found in the deeper areas (20 m) of the lake. The fish fed at all times of the year, but the number of stomachs with food and the stomach-filling indices were lowest during the darkest part of the season. The diet of smaller charr (< 15 cm) varied strongly with season, showing a dominance of zooplankton in late autumn and chironomids in winter (larvae) and summer (pupae). The food choice was in accordance with the density of food items available. Larger fish (>= 15 cm) were mostly cannibalistic during the entire year.