Footprint Impacts of BC Hydro Dams on Rainbow Trout in the Columbia River Basin, British Columbia Prepared by: Steve Arndt, M.Sc Fish and Wildlife Compensation Program – Columbia Basin 103-333 Victoria St., Nelson, British Columbia September 2009 Footprint Dam Impacts on Rainbow Trout Executive Summary The Fish and Wildlife Compensation Program (FWCP) – Columbia Basin has undertaken a project to assess the footprint impacts of BC Hydro dams in the Columbia River drainage in British Columbia. This review includes a primary productivity assessment (Moody et al. 2007), habitat gain/loss (Thorley 2008), and several species impact reviews. This report provides an impact assessment for rainbow trout, Oncorhynchus mykiss. Available information on population status before and after dams is summarized and compensation options for addressing losses are provided. Rainbow trout are a highly diverse species with respect to habitat use, life history, and phenotype. Five rainbow trout ecotypes are used to describe impacts in the basin (small-stream resident, fluvial, small lake adfluvial, large lake insectivorous, large lake piscivore). This species is arguably the most important fish in the basin in terms of its recreational and food use that contributes to quality of life and economic activities in the region. In large lakes and reservoirs, it occupies an important niche as one of the main species preying upon kokanee, Oncorhynchus nerka. Conservation status for the species as a whole is ranked as yellow (not at risk) in BC. Conservation status is not currently evaluated for individual ecotypes, but adfluvial piscivore and large river fluvial fish are relatively rare provincially. Prior to dams, rainbow trout were indigenous throughout the Columbia River drainage, and in the Kootenay River drainage below Kootenai Falls, Idaho. Introductions of rainbow trout in recent years, primarily into Koocanusa Reservoir (Montana) have resulted in an expansion into the upper Kootenay River drainage. Evaluation of footprint dam impacts was hindered by a lack of comparable information from the pre-dam era, potential interactions between footprint and operational effects, impacts of non-BC Hydro dams, and significant anthropogenic impacts not related to dams in some units including phosphorus enrichment from a fertilizer plant, and introductions of mysids, an important competitor with kokanee. As a result, in many cases it was not possible to compare population abundance in the pre- and post-dam eras, and in some cases the cause of a population change was uncertain. Nevertheless some general conclusions can be made. 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 Fish and Wildlife Compensation Program - Columbia Basin ii Footprint Dam Impacts on Rainbow Trout 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. Compensation measures proposed for loss of river habitats are by necessity off-site (i.e., in remaining rivers outside the flood zone). These include in-stream habitat and riparian restoration, reconnection of isolated habitats, and nutrient additions to enhance productivity and viability of remaining fluvial populations. Stream flow conservation through conservation water licences is proposed to protect discharge in remaining stream habitat. The East Kootenay provides many opportunities for river enhancement with a closely related indigenous species, westslope cutthroat trout, Oncorhynchus clarkii lewisi. Rainbow trout are not indigenous to this area. Preservation of existing high quality habitats through conservation covenants, land purchases, and provision of information on key habitats to resource regulators may be the most cost- effective way of ensuring the maintenance of remaining genetic and ecotypic diversity in the region. Measures to compensate for lost spawning and rearing habitat for adfluvial fish include spawning channels, stream gravel additions and artificial propagation. Before large investments are made, however, sources and levels of remaining natural reproduction should be determined to judge whether spawning and early rearing habitat is likely to be limiting to the target population. In large lake habitats downstream of reservoirs continued support for nutrient additions is recommended, as well as kokanee population management. Operational changes may also have potential to mitigate effects of upstream and downstream dams (investigated under Water Licence Requirements). Small lake enhancement projects could include habitat restoration, nutrient additions, or fish stocking in remaining lakes with fish. Also there is the possibility of developing new fishery opportunities in lakes currently without fish by introducing sterile hatchery fish, if risks to other species (amphibians, invertebrates) are low. Fish and Wildlife Compensation Program - Columbia Basin iii Footprint Dam Impacts on Rainbow Trout Table of Contents Executive Summary ....................................................................................................................................ii Table of Contents .......................................................................................................................................iv List of Tables and Figures........................................................................................................................vii 1.0 INTRODUCTION.................................................................................................................................1 2.0 METHODS ............................................................................................................................................2 2.1 Consultation and Literature Review................................................................................................................2 2.2 Definitions of Footprint Impacts ......................................................................................................................3 2.3 Societal Values Affected by Footprint Impacts...............................................................................................4 3.0 HISTORICAL DISTRIBUTION IN THE COLUMBIA RIVER BASIN ......................................5 4.0 LIFE HISTORY....................................................................................................................................7 4.1 Life History Ecotypes and Genetic Diversity ..................................................................................................7 4.2 Life History Patterns Among Ecotypes............................................................................................................9