Migrations and Habitat Utilization of Anadromous Arctic Charr Salvelinus alpinus

The stock size of anadromous Arctic charr in the River Hvítá, West Iceland, has collapsed during the last decade, possibly due to warming of both the freshwater and coastal areas in the period. The river is a mixture of glacial water, direct run off rivers and cold springs in the upper reaches. The river falls into a large estuary, with considerable tidal and salinity fluctuations. The main objective of the study was to map migration patterns undertaken by the charr population and its habitat utilization. The charr are mainly restricted to the main river channel, but important spawning grounds are found in a small spring fed tributary, 50 km upstream from the estuary. After spawning, the adult fish migrates downstream to the lower reaches of R. Hvítá and its tributaries. Frequent migrations occur between the estuary and the lower reaches of R. Hvítá during winter, but in the spring and early summer the Arctic charr stays in the estuary for a longer period. The majority of the population seems to migrate to the estuary for the first time as one and two years of age and the individuals become sexually mature mostly two to four years old.