The Chinook salmon, Oncorhynchus tshawytscha , is the largest species in the Pacific salmon(Oncorhynchus)genus. Other commonly used names for the species include king salmon, Quinnat salmon, spring salmon, and Tyee salmon. Chinook are anadromous fish native to the north Pacific Ocean and the river systems of western North America, ranging from California to Alaska. They are also native to Asian rivers ranging from northern Japan to the Palyavaam River in the Siberian far east, although only the Kamchatka Peninsula supports relatively persistent native populations. They have been introduced to other parts of the world, including New Zealand and the Great Lakes. A large Chinook is a prized and sought-after catch for a sporting angler. The flesh of the salmon is also highly valued for its dietary nutritional content, which includes high levels of important omega-3 fatty acids. Some populations are endangered, though Chinook salmon have not been assessed for the IUCN Red List.
The Chinook is blue-green, red, or purple on the back and top of the head, with silvery sides and white ventral surfaces. It has black spots on its tail and the upper half of its body. Chinook have a Black gum line which is present in both salt and freshwater. Adult fish range in size from 24 to 36 in (610 to 910 mm), but may be up to 58 in (1,500 mm) in length; they average 10 to 50 lb (4.5 to 22.7 kg), but may reach 130 lb (59 kg). The current sport-caught world record, 97.25 lb (44.11 kg), was caught on May 17, 1985, in the Kenai River (Kenai Peninsula, Alaska). Some were found dead at well over 100 lb. The commercial catch world record is 126 lb (57 kg) caught near Rivers Inlet, British Columbia, in the late 1970s.
Chinook salmon may spend one to eight years in the ocean (averaging from three to four years) before returning to their home rivers to spawn. Chinook spawn in larger and deeper waters than other salmon species and can be found on the spawning redds (nests) from September to December. After laying eggs, females guard the redd from four to 25 days before dying, while males seek additional mates. Chinook salmon eggs hatch, depending upon water temperature, 90 to 150 days after deposition. Egg deposits are timed to ensure the young salmon fry emerge during an appropriate season for survival and growth. Fry and parr (young fish) usually stay in fresh water 12 to 18 months before traveling downstream to estuaries, where they remain as smolts for several months. Some Chinooks return to the fresh water one or two years earlier than their counterparts, and are referred to as “jack” salmon. “Jack” salmon are typically less than 24 in long, but are sexually mature and return at an earlier age.
The Yukon River has the longest freshwater migration route of any salmon, over 3,000 km (1,900 mi) from its mouth in the Bering Sea to spawning grounds upstream of Whitehorse, Yukon. Since Chinook rely on fat reserves for energy upon entering fresh water, commercial fish caught here are highly prized for their unusually high levels of heart-healthy omega-3 fatty acids. However, the high cost of harvest and transport from this exceptionally rural area limits its affordability. The highest in elevation Chinook salmon migrate to spawn is in the Upper Salmon River and Middle Fork of the Salmon River in Idaho. These anadromous fish travel over 5,000 ft in elevation past eight dams on the Columbia and Lower Snake Rivers.