Event Title

Concurrent Sessions B: Case Studies - The Importance of Near-Natural Bypass Channels as Compensatory Habitat and Migration Corridors at Hydropower Plants

Location

Agriculture Production Theater, Oregon State University

Start Date

27-6-2013 10:25 AM

End Date

27-6-2013 10:45 AM

Description

Hydropower plants highly contribute to the fragmentation of rivers. Therefore many fish ladders were built. However they are often very technical and near-natural bypasses were promoted to reestablish the river corridor and act as a compensatory habitat. Although upstream migration in near-natural bypasses was often documented little is known about their use for downstream migrating fish. We studied two near-natural bypass channels: a 90 m long bypass at a small hydropower plant (Birs River) and a 1200 m long at a big hydropower plant (Aare River). To detect fish migration, we PIT tagged fish. Antennas were installed at the lower and upper end of the bypasses. 451 individuals were tagged in a bypass channel of the Aare River and 561 individuals in the Birs River. Movements were recorded between 125-140 days. Groups of translocated fishes were released upstream of the power plants in order to document downstream migrations through the bypass. The bypass in the Aare River was rich in fish species (22 species). Mainly barbels and chubs were studied. Chubs mainly migrated downstream (day and night), whereas barbels preferred to migrate at night in both directions. The migrating barbels were significantly bigger than resident barbels.14 % of the translocated fish returned into the bypass (half of them through the upper antenna). In the bypass of the Birs River we could show that the direction of migration depends on the fish length. Small brown trout were resident or migrated downstream, whereas bigger trout migrated upstream. Out of the 215 translocated brown trout only 3 % entered the bypass from the upstream direction. Our studies documented the importance of the bypass systems as compensatory habitat, and as migration corridor for upstream migrating fish. But near-natural bypass channels only had a marginal importance as a corridor for downstream migrating fish.

Comments

Armin Peter, fish ecologist, studies in biology at the Swiss Federal Institute of Technology, postdoc at the University of British Columbia, Vancouver B.C., senior researcher with the focus on river restoration and fish migration bypass channels, connectivity, fragmentation, stream restoration.

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Jun 27th, 10:25 AM Jun 27th, 10:45 AM

Concurrent Sessions B: Case Studies - The Importance of Near-Natural Bypass Channels as Compensatory Habitat and Migration Corridors at Hydropower Plants

Agriculture Production Theater, Oregon State University

Hydropower plants highly contribute to the fragmentation of rivers. Therefore many fish ladders were built. However they are often very technical and near-natural bypasses were promoted to reestablish the river corridor and act as a compensatory habitat. Although upstream migration in near-natural bypasses was often documented little is known about their use for downstream migrating fish. We studied two near-natural bypass channels: a 90 m long bypass at a small hydropower plant (Birs River) and a 1200 m long at a big hydropower plant (Aare River). To detect fish migration, we PIT tagged fish. Antennas were installed at the lower and upper end of the bypasses. 451 individuals were tagged in a bypass channel of the Aare River and 561 individuals in the Birs River. Movements were recorded between 125-140 days. Groups of translocated fishes were released upstream of the power plants in order to document downstream migrations through the bypass. The bypass in the Aare River was rich in fish species (22 species). Mainly barbels and chubs were studied. Chubs mainly migrated downstream (day and night), whereas barbels preferred to migrate at night in both directions. The migrating barbels were significantly bigger than resident barbels.14 % of the translocated fish returned into the bypass (half of them through the upper antenna). In the bypass of the Birs River we could show that the direction of migration depends on the fish length. Small brown trout were resident or migrated downstream, whereas bigger trout migrated upstream. Out of the 215 translocated brown trout only 3 % entered the bypass from the upstream direction. Our studies documented the importance of the bypass systems as compensatory habitat, and as migration corridor for upstream migrating fish. But near-natural bypass channels only had a marginal importance as a corridor for downstream migrating fish.