Previously spawned Atlantic salmon ascend a large subarctic river earlier than their maiden counterparts
Abstract:Spawning migration timing of maiden Atlantic salmon Salmo salar and previous spawners was analysed in the catches in 1989–2004 in the large subarctic River Teno in the northernmost parts of Finland and Norway. The hypothesis was that the migration timing of previous spawners and their maiden counterparts is similar, with the migration timing similar between sexes. In most cases, however, previous spawners were observed to migrate into the River Teno and its tributaries earlier than their maiden counterparts. The difference in run timing was especially evident between maiden one-sea-winter (1SW) Atlantic salmon and the corresponding group of previous spawners [1S1, 1 year at sea (1) followed by first spawning (S) and reconditioning period of 1 year (1) at sea and second spawning run] for both sexes in the River Teno and in its two tributaries. The same was also evident between 2SW maiden and 2S1 previous spawning female Atlantic salmon in the River Teno. Females showed earlier spawning migration than males both in previous spawners and maiden Atlantic salmon. Different maiden sea-age classes also showed differences in run timing as multi-sea-winter fish (2–4SW) ascended earlier than 1SW fish but the timing of 1S1 and 2S1 previous spawning females coincided. The results suggest that run timing of Atlantic salmon may not be strictly genetically fixed as previous spawners ascend earlier than they did on their first spawning migration as maiden fish, and indicated that the closeness of the reconditioning area of postspawners to the river of origin resulted in an early ascent. Run timing of different sea-age groups has major management implications if the populations are heavily exploited with numerous fishing methods in different periods of the fishing season, as in the River Teno system.
Document Type: Regular Paper
Affiliations: 1: Finnish Game and Fisheries Research Institute, Oulu Game and Fisheries Research, Tutkijantie 2E, 90570 Oulu, Finland, 2: Fisheries and Oceans Canada, Science, Oceans and Environment Branch, St John’s, Newfoundland, Canada, 3: Office of the County Governor of Finnmark, Department of Environmental Affairs, Damsveien 1, N–9800 Vadsø, Norway 4: Norwegian Institute for Nature Research, Department of Arctic Ecology, NINA Tromsø, Polar Environmental Center, N-9296 Tromsø, Norway
Publication date: October 1, 2006