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Migratory Behavior of Ascending Adult Salmon (Salmo Salar) in the Outlets of Hydropeaking Power Plants

Author(s): Teppo Vehanen; Aki Maki-Petays; Ari Huusko; Panu Orell

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Abstract: The effect of dams on natural river ecosystems has been damaging. Dams change both the geomorphology and hydrology of rivers. For the anadromous fish species, like the Atlantic salmon (Salmo salar), dams are alsomigratory barriers. In situations when it is not possible to remove a migratory barrier, a fishway or a by-pass channel is constructed to allow fish-passage. For the planning of fish-passage structures it is important to know the patterns of fish behaviors below the dam: when fish are actively finding the way upstream. Upstreammigration may also be guided by environmental factors, like changes in discharge. In this study we used telemetry to study the migration patterns of ascending adult salmon in two large rivers in Finland, RiversKemijoki and Iijoki. Altogether 121 salmon were captured during their spawning run, tagged with telemetry tags, and released below six hydropower stations in small groups. Stationary telemetry antennas were used to observe fish behavior below the dams. A clear pattern was found as fish moved upstream below the dam at higher discharge during daylight and descended downstream at lower discharge and darkness. The effect of temperature was less significant. Our results add to knowledge needed in re-building of salmon stocks inregulated rivers.


Year: 2018

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