There were a lot of really important decisions throughout the 1900's that had huge impacts on natives and their right to fish and when and where they could fish. The Treaty of Olympia signed in 1855 stated that "tribes had the right to take fish as at all usual and accustomed grounds and stations in common with all citizen of the territory."

The years following the signing of the treaty included the decimation of the salmon and steelhead fisheries, along with the natives right to fish, where they could fish, how they could fish, and how much fish was available for them to take. We have to remember that the natives in the PNW gave up literally everything they had for a small parcels of land and the right to fish. Imagine telling your invaders "we'll give in, you can have it all, we just want a place to live and our source of fish to remain available so we can eat."
The fisheries in the PNW were literally destroyed in the 1800's and 1900's by Euro Americans and the settlers arriving from the East. Most of the decimation came from poor management, hatcheries, dams, over harvest, logging, etc. Salmon and steelhead fisheries went from plentiful to scraps, and not just for the natives, but for everyone. As fisheries began to degrade, hate, racism, and rights violations against the natives and their take of the fish began to pile on. Commercial fisheries were taking so many fish in the ocean that there was hardly anything left for the natives once the fish reached the rivers. 
During the late 1930's and early 1940's, citizens became more frustrated with the decline fisheries and lashed out at the natives stating "the Indians are not citizens and therefore have no right to fish without a state fishing licenses." This was a clear treaty violation and was eventually taken care of in Tulee vs Washington in 1942. By no means did the Natives need a "state" fishing licenses to fish. That's just messed up!

Through the 1960's and early 1970's brought even more violations to tribes treaty rights. Government agencies spouted that when tribal members fished outside their reservations on state grounds, that they tribes were not allowed to used traditional nets and traps. When caught using these techniques, natives were arrested and prosecuted. Native Americans protested and would have "fish-ins" where they would fish the rivers using their native techniques until removed. 

In 1968/69 Judge Belloni upheld the right for natives to fish in their "usual and accustomed places" in the case sohappy vs smith/U.S. vs Oregon. Before the ruling, 14 Yakima fishers were cited and harassed for fishing outside of the "state" fishing season.

From 1974-1980 was the process and ruling of United States vs Washington, a.k.a. the Boldt Decision. The cliff notes of this ruling include that tribes had the right to "half of all available fish". In typical American fashion, citizen argued that hatchery fish should not and would not be included in the decision because the hatchery fish are "owned" by American citizen. This is where judge Boldt would later on add the piece "all available fish." In general, the Boldt decision was a major win, at the time, for the tribes of Washington.