Lake Sammamish Late-Run Kokanee Spawning Ground Survey And Escapement Estimate.pdf

## Lake Sammamish Late-Run Kokanee Spawning Ground Survey Summary & Escapement Estimate (Chad Jackson, 2010)

Background:

Lake Sammamish Watershed supports three distinct kokanee populations: early, middle, and late runs.
Early-run kokanee were once abundant but have declined dramatically and are now considered functionally extinct.
Middle-run kokanee are genetically contaminated with Baker Lake sockeye genes.
Late-run kokanee are the only remaining native population in the watershed and are a conservation focus.

Study Objective:

Estimate late-run kokanee spawner escapement into south Lake Sammamish tributaries (Lewis, Laughing Jacobs, Ebright, Pine Lake creeks) during the 2009-10 spawning run.
Assess long-term escapement trends in these tributaries.

Methods:

Bi-weekly to daily surveys of selected tributaries from October through early February.
Live and dead fish counts, biological sampling (fork length, sex, otoliths, DNA), and brood stock collection.
AUC (area under the curve) methodology used to estimate escapement based on live fish counts over time.
Stream life value of 10 days used initially; range estimated using alternative stream life values (5, 7, 12 days).

Results:

Lewis Creek:
First observed November 6, last seen January 29.
Peak count on January 7 (181 kokanee).
Total fish-days: 4,711 (10-day stream life) = estimated escapement of 471 fish.
Lower than all years (1997-2008) average but about three times greater than recent 4-year average.
Escapement range: 393 to 942 fish based on alternative stream life values.
* Other tributaries (Laughing Jacobs, Ebright, Pine Lake): Data summarized but not presented in detail in the provided text excerpt.

Conclusion:

The study provides valuable data on late-run kokanee escapement in south Lake Sammamish tributaries during the 2009-10 spawning season. Results highlight variability in escapement levels and underscore the need for continued monitoring and management efforts to protect this remaining native kokanee population.