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Report: Yalakom River Fish Inventory Update COA-F20-F-3030

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The Bridge River project was developed in the 1940s to provide hydropower to the greater Vancouver area. The project is comprised of two dams; LaJoie Dam, located on the upper river near GoldBridge, B.C., and Terzaghi Dam, located 40 km upstream from the Bridge Rivers confluence with the Fraser River.

Author:  Coldstream Ecology Ltd. Melissa Evans

Old Reference Number:  COA-F20-F-3030

Old Reference System:  FWCP - Fish Wildlife Compensation Program Coastal

Date Published:  Mar 2020

Report ID:  58709

Audience:  Government and Public

Terzaghi Dam was designed to hold and divert all water from the Upper/Middle Bridge River to hydropower generating stations in the adjacent Seton River watershed; however, two major operational changes have occurred at Terzaghi in recent years: (1) the initiation of continuous flow releases from the dam, and (2) nearannual high-flow spill events. The effects of flow releases on the aquatic ecosystem downstream of Terzaghi Dam are complex but have included declining juvenile salmonid fish abundances. The Yalakom River is the only salmonid fish-bearing tributary downstream of Terzaghi Dam and as such, has been posited as potential refuge and enhancement area for the salmonid fishes impacted by hydropower operations on the mainstem Bridge River. However, recent information on salmonid fish species occurrence and habitat use in the Yalakom River is lacking. This project is aimed at updating salmonid fish occurrence and distribution data for the Yalakom River, with the longer-term goal of informing restoration planning processes for the Yalakom-Lower Bridge watershed. During October 2019, we conducted electrofishing surveys at 12 spatially distributed sites on the Yalakom River. In total, we documented four fish species; Chinook salmon (Oncorhynchus tshawytscha) and coho salmon (O. kisutch), bull trout (Salvelinus confluentus), and O. mykiss (rainbow trout/steelhead). Bull trout and rainbow trout/steelhead were the most abundant and widelydistributed species observed during our surveys. Coho and Chinook salmon were observed in the lower Yalakom River and at relatively low abundances. We were unable to sample above river km 32 because cold water temperatures precluded the implementation of electrofishing surveys; thus, fish habitat use in the upper Yalakom River will require additional research. In future years, we recommend that juvenile surveys be conducted in the spring and late summer months, which would allow for sampling of emerging salmon and O. mykiss fry, respectively. Additional, complementary survey modalities should also be considered in future years, including the use of eDNA technology and spawning ground surveys, which would improve our ability to identify critical habitats for natural production and rearing and provide insight into the potential impacts of putative fish passage obstructions within the Yalakom River on spawning/rearing habitat use.

Report Type
  Fish and Aquatic Habitat Information
  Fish Species - Bull Trout - Salvelinus confluentus
  Fish Species - Chinook Salmon - Oncorhynchus tshawytscha
  Fish Species - Coho Salmon - Oncorhynchus kisutch
  Fish Species - Rainbow Trout - Oncorhynchus mykiss
  Region - Thompson-Nicola
  Fish and Fish Habitat - Fish Inventory
  Watershed Groups - 100 - Fraser

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