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Conservation of Lake Sammamish Kokanee An Update on Current Science

This briefing provides insight into ongoing research on Lake Sammamish Kokanee focusing on spawning, food webs, supplementation, tagging studies, and future conservation efforts like stream habitat assessment and release strategies. Analysis of fish movement, habitat conditions, and water quality are key components. Data suggests challenges due to reduced optimal habitat caused by temperature and dissolved oxygen variations in the lake affecting fish growth. Emphasis on important habitats like streams, deltas, and predation areas highlight the need for conservation actions. Acoustic telemetry project goals include understanding fish movement and predator-prey interactions. Limnological measurements and fish collection methods are crucial for data collection and analysis, aiding in conservation planning. Efforts such as tagging and acoustic tracking have shown positive results in detecting fish movements in Lake Sammamish, with detections in key areas near the Bellevue shoreline. This comprehensive update aims to inform the Planning Commission for effective conservation strategies.

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Conservation of Lake Sammamish Kokanee An Update on Current Science

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  1. Conservation of Lake Sammamish Kokanee An Update on Current Science A Briefing for the City of Bellevue Planning Commission Hans Berge– King County Department of Natural Resources and Parks hans.berge@kingcounty.gov November 4, 2009

  2. Kokanee Science To Date: Spawning ground surveys (annually since 1996) Food web research within the lake (2002-2005) Fry trapping on Lewis Creek (annually since 2007) Current: Supplementation (Fall 2009) Tagging study (2009-2010) Future: Stream habitat assessment Project prioritization Release strategies Colonization in other spawning streams Effects of hatchery releases from Issaquah Creek

  3. Kokanee growth is reduced in the summer • Relative weight (Wr) used to measure condition • Species specific values for cutthroat and kokanee (Hyatt and Hubert 2000) • Cutthroat trout Wr was greater during stratification (t-test, p<0,002) • Kokanee Wr was lower during stratification and the DO squeeze (t-test, p<0.001)

  4. Optimal habitat is reduced by temp-DO squeeze 20% of the lake is <17°Cand >4 mg/L

  5. Important Habitats Streams (spawning and incubation) Lewis Vasa Shoreline of Lake Sammamish (early rearing, upstream migration) Deltas Early rearing of fry Predation Lake Sammamish (rearing and maturation) Water Quality Phosphorous Nitrogen

  6. Lewis Creek Example High flows Bed stability/mobility Infrastructure risk Floodplain connectivity Flood refuge Pool formation Energy dissipation Kokanee redd

  7. Upper Lewis Creek (above I-90) Erosion, high flows, good riparian condition

  8. Lower Lewis Creek (below I-90)

  9. Acoustic Telemetry Project Project Goals: Understand seasonal movement of kokanee in Lake Sammamish Monitor spatial and temporal overlap of limnetic predators and prey Investigate the effects of thermal stratification, zooplankton density, and diel period on movement of kokanee

  10. HydrophoneDeployment

  11. Limnology Clarke-Bumpus zooplankton sampler • Limnological Measurements • Temperature, DO • Light and turbidity • Secchi Depth • Monthly zooplankton SCAMP (Temp and Light) Monitoring Buoys (Temp, DO) Secchi (transparency))

  12. Fish Collection Transferred to livewell TU anglers helped catch fish Careful handling

  13. Acoustic Tagging Boat Anesthetic Processing Table Length and Weight Tag inserted Sutures to close incision Recovery in insulated tank and released

  14. Results to Date Analysis in progress… 35 tagged fish Downloaded data every other month beginning in August Have heard from 33 fish Detections at all 4 stations near Bellevue shoreline (and all but one other station) Kokanee adults found in littoral and limnetic zone of Lake Sammamish

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