Final answer:
Salmon was an important source of protein for the Pacific Northwest peoples, as this fish was abundant and a dietary staple.
Step-by-step explanation:
The question pertains to the source of protein for the people of the Pacific Northwest. Among the options presented, salmon is known to have been an important source of protein for these people. The Pacific Northwest is a region rich in marine life and salmon, specifically, played a vital role in the diet and culture of Native American tribes in this area. They relied on fishing and the annual salmon runs, which provided an abundant and reliable source of high-quality protein.