Chinook Salmon. Chinook (Oncorhynchus tshawytscha), also known as King Salmon, is the largest of the salmonids in RNSP streams measuring 24 to 36 inches (610 to 1,058 mm; but may be up to 58 inches (1,500 mm)) in length; they average 10 to 50 lbs (4.5 to 23 kg), but may reach 100 pounds (45 kg).