1 Nez Perce Tribe, Department of Fisheries Resources Management, P.O. Box 365, Lapwai, Idaho, 83540, USA

✉ Correspondence: Jay A. Hesse <>, Ryan N. Kinzer <>

Suggested Citation for Annual Results:
Hesse, J.A. and Kinzer, R.N., 2026. Snake River Anadromous Fish Status: Quasi-Extinction Threshold Analysis. Department of Fisheries Resources Management. Version: 14 May, 2026. Available: https://ryankinzer.github.io/SRAFS/

1 Quasi-Extinction Summary

Updates for the 2025 analysis:

  • Removed Little Salmon River from spring/summer Chinook Salmon analysis due to limited data from only a small portion of the population.
  • Included multiple time-series of observations for each population if available (i.e, spawning ground survey data, weir observations, PIT-tag based estimates)
  • Performed model selection on multiple candidate models with varying numbers of state processes, drift, process error, and observation error parameters
  • PIT-tag based estimates now include an expansion for available habitat not covered by the instream PIT-tag detection system (Ackerman et al. 2026, in prep)

1.1 Spring/summer Chinook Salmon

Natural-origin (wild) and hatchery-origin returns of Snake River spring/summer Chinook Salmon past Lower Granite Dam.

Figure 1.1: Natural-origin (wild) and hatchery-origin returns of Snake River spring/summer Chinook Salmon past Lower Granite Dam.

Table 1.1: The table provides summary counts of spring/summer Chinook salmon populations currently below minimum abundance thresholds, 50 spawners, and meeting the quasi-extinction threshold (4 consecutive years below 50 spawners), and the number of populations predicted to fall below 50 by return year 2030.
Metric All Snake River Populations Extant ESA-listed Populations
Populations 34 31
Below Minimum Abundance Threshold 32 (94%) 29 (94%)
Current Return Below 50 7 (21%) 7 (23%)
Currently Below Quasi-Extinction Threshold 3 (9%) 3 (10%)
Predicted Below 50 by 2030 8 (24%) 8 (26%)
Current status of natural-origin Snake River spring/summer Chinook Salmon relative to the quasi-extinction threshold (QET) and Columbia Basin Partnership goals.

Figure 1.2: Current status of natural-origin Snake River spring/summer Chinook Salmon relative to the quasi-extinction threshold (QET) and Columbia Basin Partnership goals.