I do not understand how the tribes can be given credit for this fishery. Did they build the Ballard Locks?? Here is an excerpt from the WDFW web-site.

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Prior to the 1930s, Lake Washington was famous for its large populations of kokanee (the freshwater form of the sockeye), but sea-run sockeye salmon were thought to be absent. In the year 1916, the ship canal was opened to serve as a new outlet for Lake Washington and to provide the water needed to operate the just completed Hiram M. Chittenden Locks at Ballard. This combined the extensive spawning grounds of the Cedar River with a large lake rearing environment, provided an opportunity to develop a major sockeye salmon population in the waters of southern Puget Sound.

Sockeye were introduced into the Lake Washington watershed in 1935 (and subsequent years) from the Baker River.
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I do not think the tribes had anything to do with this effort, and their treaty, written 50 years previous, could not have included it. But somewhere along the way they looked under the Christmas tree and there was this fishery handed to them.