Summary of George River Pacific Salmon Smolt Study

Funded By:

Donlin Gold LLC

2525 C St Suite 450

Anchorage, AK 99503

Study Completed By:

The Native Village of Napaimute

P.O Box 107

Aniak, AK 99557

www.napaimute.org

Owl Ridge Natural Resource

Consultants, Inc.

4060 B Street, Suite 200

Anchorage, AK 99503

What was studied?

  • A 2-year proof-of-concept study to understand salmon smolt outmigration on the George River.

Sampling Period

  • May 8 through June 18, 2025

Goal

  • Estimate juvenile salmon abundance and test monitoring methods.

Methodology

  • Sampling sites: Located upstream of the ADF&G salmon weir based on existing infrastructure and known salmon runs.

  • Fish capture: Two 8-foot rotary screw traps (riverbank + mid-river) captured out-migrating juvenile salmon.

  • Fish handling: Fish identified by species, measured for length and weight, and temporarily held in aerated containers.

  • Release method: Fished released upstream at night to match natural migration behavior.

  • Mark-recapture: used to estimate total smolt abundance.

  • Environmental data: water temperature, water level, dissolved oxygen, and conductivity recorded using standardized methods.

  • Data analysis: Population estimates calculated using time-stratified, Bayesian mark-recapture models.

  • Model adjustments: Models accounted for missed sampling days and migration outside trap deployment dates.

Results

  • 41 days of sampling

  • 13,281 fish captured

  • Species documented

    -Chinook

    -Chum

    -Coho (most abundant)

    -Pink (most abundant)

    -Sockeye (least abundant)

  • Abundance estimates

    -Chinook (age 1+): ~49,000-108,00

    -Chum (young-of-year): ~185,000-495,000

    -Coho (age 1+): ~67,000-108,000

  • Trap performance

    -Chinook & Coho: Recapture rates high enough for reliable population estimates

    -Chum: Lower recapture rates led to higher uncertainty

  • Migration timing

    -Chinook & chum peaked in late May

    -Coho & pink peaked in early June

    -Chum migration likely extended beyond sampling period

Key Takeaways

  • Smolt monitoring on the George River is feasible and effective.

  • Juvenile salmon production appears lower than comparable rivers.

  • Multiple years of data are needed to better understand trends and drivers.

Data That Tells a Story

LINK BELOW TO FULL REPORT

Final George River Pacific Salmon Smolt Study

References

  • Alaska Salmon Research Task Force Report. 7/17/2024. Numerous agencies. https://www.fisheries.noaa.gov/s3//2024-07/alaska-salmon-research-task-force-0717.pdf

  • Boersma, J.K., K.C. Harper and L.G. Coggins Jr,. 2019. An assessment of Kwethluk River Chinook salmon freshwater production.

  • Project Final Product, submitted to the Arctic-Yukon-Kuskokwim Sustainable Salmon Initiative.

  • Bonner, Simon J., and Carl J. Schwarz. "Smoothing population size estimates for time-stratified mark–recapture experiments using

  • Bayesian P-splines. " Biometrics 67, no. 4 (2011): 1498-1507.

  • Burril, Sean E., Cristian E. Zimmerman, James E. Finn, and Daniel Gillikin.

  • "Abundance, timing of migration, and egg-to-smolt survival of juvenile chum salmon, Kwethluk River, Alaska. " Open File