Growth benefit from habitat change by juvenile high-Arctic char

Migration and growth by parr of Arctic char Salvelinus alpinus were studied in the high-Arctic Dieset watercourse (79 degrees 10'N) on Spitsbergen Island, Svalbard, Norway. Our results showed a rapid parr emigration from the lake into the river during the ice breakup in late June. The habitat change was almost completed by mid-July for parr with body lengths ranging from 70 to 180 mm. Migrating parr were 2-8 years of age and 63-200 mm in length, whereas parr remaining in the lake were 0-4 years old and 23-116 mm in length. Parr migrating into the river were significantly larger than lake-dwelling parr of corresponding age. The migrating parr exhibited a mean daily increase in body weight from 1.22% (age 3 years) to 0.37% (age 8 years). Our results indicated that an early descent into the river is favorable for a body weight increase.