Whitehorse Fish Ladder, Yukon, Canada |
The number of chinook salmon that reached the Whitehorse fish ladder this year hit a 40-year low, and it's not clear why. Just 282 chinook passed through the fish ladder this year, compared to 690 last year. "We did see some large pre-spawn mortality die-offs in a tributary of the Yukon River — the Koyukuk in Alaska. This was for summer chum, and not chinook — but we expect that that higher water temperature also affected the chinook migrating through."