Record/What Is Killing Them/Prey Decline
02 — What Is Killing Them
Prey DeclinePrey Decline
The Southern Residents are starving, and the reason is Chinook salmon.
Severity scorecard
Scored 2026-09-07Severity rating
5 / 5 · Critical
- Trend
- Worsening
- Mechanism
- High confidence
- Lag to effect
- 5–20 yr
- Scored
- 1 July 2026
What would move thisChinook escapement above the ten-year mean for three consecutive returns.
Assessment
Chinook are the largest and fattiest Pacific salmon, and the Southern Residents evolved around them. Chinook runs across the Columbia, Fraser and Sacramento systems are a fraction of their historical size, cut down by dams, habitat loss, warming rivers and a century of overfishing.
Hungry orcas metabolise their own fat reserves, and that releases stored contaminants back into the bloodstream at exactly the wrong moment. Malnutrition and toxic load are not separate problems; one triggers the other.
Pregnancy is where it shows first. Studies using hormone analysis of floating scat suggest a majority of detectable pregnancies fail, most often late in gestation, and nutritional stress is the strongest predictor.
Key points
6 observations- 01Chinook runs at a fraction of historic size
- 02Dams block hundreds of miles of spawning habitat
- 03Warming rivers kill eggs and smolts
- 04Starvation releases stored contaminants
- 05Most detected pregnancies fail
- 06Recovery requires whole watersheds, not gestures