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A couple of weeks ago, a biologist from the Puyallup Tribe of Indians found an unusually large juvenile chinook salmon that was migrating out of the Puyallup River oddly late.

While most juvenile chinook the tribe counts and measures at the trap are around 3.5 inches and are only a few months old, this chinook was over eight inches long and had obviously been in the river for almost two years.

The timing of the fish’s migration was way off. “He was moving down the river long after most adult chinook had moved up,” Marks said. “Usually, we see these young chinook move down in the spring and early summer. I can’t think of a reason in nature this fish would be moving down so late.”

Tribal biologist Eric Marks found the large young chinook while monitoring a smolt trap at the Electron hydroelectric plant in mid-November. Smolt traps are used to safely capture young salmon to determine how many young fish are leaving the river system. The tribe works with the hydroelectric plant’s owners – Electron Hydro LLC – to monitor fish populations in the upper Puyallup River where the plant is located.

Marks said the fish was going through the smoltification process, getting ready to move from a freshwater to an ocean environment. Its scales had already gone chrome and the chinook’s tale had taken on a forked shaped. “If you would’ve caught this guy in the river, you would have thought he was a very young returning adult,” Marks said.

“The lesson here is that these fish have such a varied life history, you can never really tell when a fish might be in the river,” Marks said.