Downstream migration of landlocked Atlantic salmon smolt in a regulated river-Effects of multiple passage at dams with programmed spill

Abstract

In many rivers, downstream-migrating salmonid smolts must pass multiple dams often with high losses as a result. Fish experience mortality both in dam and reservoir passage, and spilling water might allow fish to avoid turbine passage and hence increase migration survival. In River Klaralven, Sweden landlocked Atlantic salmon smolts migrate along a 180 km long reach passing eight dams. A previous telemetry study estimated an accumulated migration success of 16% under conditions with no or very little spill. Here we repeat this study, under a planned spill regime at a subset of hydropower dams. Overall passage success through the eight dams was 32%, which is greater than the 16% reported from the same river section in a year without spill. Most of this increase, however, was attributable to the situation at one dam, where spill constituted a large proportion of total discharge. In addition, we found that loss rates km-1 were similar over dammed reaches and the lentic habitats, but greater than in the free-flowing reference reaches. Results for migration speed paralleled this result with the highest speeds observed in the free-flowing reaches.

Keywords

acoustic telemetry; dammed river; fish passage; migration success; Salmo salar

Published in

River Research and Applications
2024, volume: 40, number: 5, pages: 821-833
Publisher: WILEY

SLU Authors

• Nyqvist, Daniel

  • Karlstad University
  • Politecnico di Torino

UKÄ Subject classification

Fish and Wildlife Management
Oceanography, Hydrology, Water Resources

Publication identifier

• DOI: https://doi.org/10.1002/rra.4276

Permanent link to this page (URI)

https://res.slu.se/id/publ/139654