Return migration of Atlantic Salmon in the River Tana: Phases of migratory behaviour |
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Authors: | F. Ø klamd,§ ,J. Erkinaro,&dagger ,K. Moen,&Dagger ,E. Niemelä ,¶ ,P. Fiske,R.S. McKinley,| E. B. Thorstab |
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Affiliation: | Norwegian Institute for Nature Research, Tungasletta 2, No-7485 Trondheim, Norway;Oulu Game and Fisheries Research, Finnish Game and Fisheries Research Institute, Tutkijantie 2, FIN-90570 Oulu, Finland;Department of Environmental Affairs, Office of the County Governor of Finnmark, Damsveien 1, No-9815 Vadsø, Norway;River Tenojoki Fisheries Research Station, Finnish Game and Fisheries Research Institute, FIN-99980 Utsjoki, Finland;Department of Biology, University of Waterloo, Waterloo, Ontario, Canada, N2L 3G1 |
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Abstract: | From a total of 174 multi-sea-winter Atlantic salmon radio tagged in the Tanafjord (northern Norway, 70°N) during 1992 and 1993, 48 Atlantic salmon were followed from entering the River Tana until spawning. Three phases were identified: (1) migratory, direct or stepwise migration to, or close to the position held at spawning; (2) search, movements both up and down river at or close to the position held at spawning; (3) holding, a period without movements prior to spawning. During the migratory phase, Atlantic salmon migrated directly to near the spawning area, or stopped between one and nine shorter periods during the upstream migration. Number of stops increased with increasing migratory distance in 1993, but no such correlation was found in 1992. The highest migratory speeds were recorded in the lower parts of the river. A distinct change in migratory pattern was found in 67% of the Atlantic salmon near or at the area held at spawning. Most common was a search phase of erratic movements with more than one down river movement. After the movement terminated, 96% of the Atlantic salmon had a period when no or little movement was recorded until spawning (on average 55 days in 1992 and 51 days in 1993). There was no preference for staying at, up or down river from the spawning area during this holding period. Early ascending Atlantic salmon migrated to spawning areas further from the mouth than the later arriving Atlantic salmon in 1993, but not in 1992. The proportion of time spent on the migratory phase increased, while the proportion of time spent on the holding phase decreased with increasing distance to the spawning area. |
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Keywords: | Salmo salar migratory behaviour spawning radio tagging telemetry |
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