Water Stewardship Information Sources
| ID | 121 |
|---|---|
| Citation | BC Hydro. 2012. Bridge-Seton Water Use Plan: Monitoring Terms of Reference - BRGMON-14: Deffectiveness of Cayoosh Flow Dilution, Dam Operation and Fishway Passage on Delay and Survival of Upstream Migration of Salmon in the Seton-Anderson Watershed. BC Hydro. |
| Organization | BC Hydro |
| URL | https://www.bchydro.com/content/dam/hydro/medialib/internet/documents/planning_regulatory/wup/lower_mainland/2012q2/brgmon-14_tor_2012-01-23.pdf |
| Abstract/Description or Keywords | The Seton-Anderson watershed is affected in several ways by the Bridge Hydroelectric Complex. The system includes an inter-basin diversion into Seton Lake, a diversion dam on the lower Seton River, a fishway to facilitate upstream passage at Seton Dam, and a penstock and powerhouse outflow into the Fraser River. The watershed supports populations of several fish species including five species of anadromous Pacific salmonid (BC Hydro, 2000). Of the anadromous fish, two populations of sockeye salmon (Oncorhynchus nerka), the Gates Creek and Portage Creek stocks, spawn upstream of Seton Dam and both have had declining spawning escapements in recent cycles. Coho salmon (O. kisutch), Chinook salmon (O. tshawytscha) and steelhead trout (O. mykiss) are known to migrate through the fishway though they are in relatively low abundance. Pink salmon (O. gorbuscha) is very abundant and can ascend the fishway (Pon et al. 2011) but also spawn downstream of the fishway in artificial spawning channels and in the mainstem of the Seton River. Along their migration route through the Seton-Anderson watershed, adult migrants pass several locations that may slow, impede, or otherwise cause them physiological or energetic challenges. First, they must pass a powerhouse tailrace that discharges home-stream Seton Lake water into the Fraser River ~1200 m downstream of the confluence of the Seton River. Telemetry and tagging studies by the International Pacific Salmon Fisheries Commission (IPSFC) conducted in the late 1970s and early 1980s (summarized in Fretwell 1989) with adult sockeye indicated that fish often stopped their upstream migration at, and were injured in, the tailrace - their success rate in departing the tailrace, entering the Seton River, and reaching the dam ranged considerably depending on the Seton River water characteristics. The Seton River is a mixture of Seton Lake water and Cayoosh Creek water with relatively high Cayoosh Creek dilution levels resulting in high migration failure for adult sockeye salmon; pink salmon were less affected by dilution levels (Fretwell 1989). Even at the IPFSC recommended (Fretwell 1989), and BC Hydro adopted, Cayoosh Creek dilution levels of 20% and 10% during the Gates and Portage sockeye migrations, respectively, migration failure rates of ~ 8% and 28% for these stocks respectively, occurred in the IPFSC studies (Fretwell 1989). Once adult salmon enter the Seton River, they must travel 5 km to, and ascend, the Seton Dam Fishway then, depending on species and stock, migrate through Seton Lake (and potentially Anderson Lake) to spawning grounds. Previous tagging studies have documented migration rates, but concerns on handling effects and re-location effects on tagged fish have been raised, and are important to consider in evaluating results. In a 2007 study, 52% of tagged Gates sockeye perished between the Seton River and spawning grounds with over half of that loss (32%) occurring between the Fraser River and the fishway (Roscoe and Hinch 2008). Females suffered nearly twice as high mortality compared to males during migration to spawning grounds. Of the sockeye that passed the dam and entered Seton and Anderson lakes, total inlake mortality was 33% for fish released at the powerhouse tailrace, compared to 19% for fish released in the lower Seton River, and 7% for fish released upstream of the dam. Therefore, the migration experience through the lower river and the fishway may contribute to mortality later during the migration. Migration experience prior to arriving at the Seton system (e.g., migration in Fraser River) may also contribute to mortality later during the migration. The cause of in-lake mortality is not known (Roscoe and Hinch 2008). aquatic habitat, dam, reservoir, salmonid, fish passage |
| Information Type | report |
| Regional Watershed | Fraser |
| Sub-watershed if known | Anderson Lake, Seton Lake |
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| Comments | |
| Project status | complete |
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