Return migration of one-sea-winter Atlantic salmon in the River Tana

摘要

Fifty-three one-sea-winter Atlantic salmon Salmo salar (45-63 cm L-T) were radio-tagged in the Tana fjord, Barents Sea, in 1995. Thirty-seven fish (70%) entered the freshwater zone of the River Tana in an average of 3 days after release in the fjord. The migration speeds in the lowest river section below the first riffle area were significantly higher than in the subsequent river section below the second riffle area. Similarly, the observed time spent in the first riffle area was significantly lower than in the next riffle area. The majority of Atlantic salmon entered the river during the hours of high tide and the subsequent ebb tide. In addition, most river entries were recorded around midnight. No effects of river flow on the river entry or migration speed were detected, but the migration speed of Atlantic salmon in both river sections examined was greater at lower temperatures. Twenly-eight fish (72%) were recaptured in the river, 71% of them with weirs and gillnets, and 29% by rod and line. Over half of the Atlantic salmon (54%) were recaptured within 3 weeks following river entry, and within the first 100 kin of the river (56%). The results are discussed in relation to earlier studies oil multi-sea-winter Atlantic salmon in the River Tana