Duck

When Tacoma was doing the required fish studies on the Cowlitz a couple of years ago, it was revealed that 25% of all the fall chinook that were spawning naturally in the Cowlitz Rivers were strays from the Lewis River. Apparently fish stray way more then originally believed, especially fall chinook on the Cowlitz.

To me, that would indicate that it appears that each river system may vary highly depending on the species and river.

Cowlitzfisherman