Footprint Impacts of BC Hydro Dam on Rainbow Trout in the Columbia River Basin

Author: S. Arndt

Distribution and abundance of the fluvial ecotype in the basin has been greatly reduced due to inundation of most of the large river and some medium-sized river habitat from Kinbasket Reservoir downstream to Keenleyside Dam. Significant remaining fluvial populations in the West Kootenay are limited to the remaining 68 km of the Columbia/Kootenay rivers downstream of Keenleyside and Brilliant dams (robust population) and small populations in the Salmo and Slocan rivers. This major, direct impact of dams has not been addressed by the FWCP to date, except on a very small scale.

Loss of access to stream habitats due to inundation or blocked migration also significantly reduced spawning and rearing habitats for adfluvial ecotypes (insectivorous and piscivorous) with uncertain effects on their abundance in associated lakes and reservoirs. Major habitat losses affected trout from Arrow and Kootenay lakes, the two most important large lake habitats in the basin. In the Arrow lakes, a unique indigenous “yellowfin” rainbow trout was extirpated. These fish are believed to have spawned in Camp Creek above Mica Dam; access to their historical adult habitat was blocked, and Kinbasket Reservoir apparently was not suitable for their survival at least in the early years. In Kootenay Lake, an important spawning area for piscivorous adfluvials was lost due to Duncan Dam. Recent observations have shown that some spawning persists below the dam; however, it is not known whether these fish are the same (genetically) as the original stock. In addition to the losses of stock diversity, abundance of piscivores may have declined without intervention to support the prey species, kokanee, which was affected by changes in the productivity of Kootenay and Arrow lakes related to nutrient retention in upstream dams.

Extensive fragmentation by dams has blocked historical habitat connections that previously allowed extensive migrations and interactions between fluvial and adfluvial populations in different parts of the basin. This has resulted in a substantial reduction in rainbow trout life history diversity with accompanying reductions in phenotypic and likely genetic diversity. Genetic integrity has also been compromised in Arrow Lakes Reservoir by stocking programs aimed at compensating for lost natural production. Isolated fluvial populations (e.g., Salmo River) may be less productive because they no longer have access to larger river habitats.

Several small-lake adfluvial populations were lost due to inundation of their habitats, including some productive lakes capable of producing fish >2 kg. Loss of river fishery options and small lakes represent a significant lost opportunity for the region in terms of fisheries management, recreation, and biodiversity. The stream-resident ecotype was affected to a relatively minor degree by habitat loss because they are typically found above the flooded zone, however, smaller hydropower plants that divert water from upper stream reaches have reduced stream capacity in some areas.

Distribution and abundance of the fluvial ecotype in the basin has been greatly reduced due to inundation of most of the large river and some medium-sized river habitat from Kinbasket Reservoir downstream to Keenleyside Dam. Significant remaining fluvial populations in the West Kootenay are limited to the remaining 68 km of the Columbia/Kootenay rivers downstream of Keenleyside and Brilliant dams (robust population) and small populations in the Salmo and Slocan rivers. This major, direct impact of dams has not been addressed by the FWCP to date, except on a very small scale.

Loss of access to stream habitats due to inundation or blocked migration also significantly reduced spawning and rearing habitats for adfluvial ecotypes (insectivorous and piscivorous) with uncertain effects on their abundance in associated lakes and reservoirs. Major habitat losses affected trout from Arrow and Kootenay lakes, the two most important large lake habitats in the basin. In the Arrow lakes, a unique indigenous “yellowfin” rainbow trout was extirpated. These fish are believed to have spawned in Camp Creek above Mica Dam; access to their historical adult habitat was blocked, and Kinbasket Reservoir apparently was not suitable for their survival at least in the early years. In Kootenay Lake, an important spawning area for piscivorous adfluvials was lost due to Duncan Dam. Recent observations have shown that some spawning persists below the dam; however, it is not known whether these fish are the same (genetically) as the original stock. In addition to the losses of stock diversity, abundance of piscivores may have declined without intervention to support the prey species, kokanee, which was affected by changes in the productivity of Kootenay and Arrow lakes related to nutrient retention in upstream dams.

Extensive fragmentation by dams has blocked historical habitat connections that previously allowed extensive migrations and interactions between fluvial and adfluvial populations in different parts of the basin. This has resulted in a substantial reduction in rainbow trout life history diversity with accompanying reductions in phenotypic and likely genetic diversity. Genetic integrity has also been compromised in Arrow Lakes Reservoir by stocking programs aimed at compensating for lost natural production. Isolated fluvial populations (e.g., Salmo River) may be less productive because they no longer have access to larger river habitats.

Several small-lake adfluvial populations were lost due to inundation of their habitats, including some productive lakes capable of producing fish >2 kg. Loss of river fishery options and small lakes represent a significant lost opportunity for the region in terms of fisheries management, recreation, and biodiversity. The stream-resident ecotype was affected to a relatively minor degree by habitat loss because they are typically found above the flooded zone, however, smaller hydropower plants that divert water from upper stream reaches have reduced stream capacity in some areas.