The largest species in the Pacific salmon (Oncorhynchus) genus. 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. Its mouth is often dark purple to black. Adult fish range in size from 610 to 910 mm but may be up to 1,500 mm in length; they average 4.5 to 22.7 kg, but may reach 59 kg.

Born in rivers and streams, matures in the sea anad returns to freshwater to breed.

Salmon feed on planktonic diatoms, copepods, kelps, seaweeds, jellyfish, and starfish. As with all salmonid species, they also feed on insects, amphipods, and other crustaceans while young, and primarily on other fish when older.

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 through 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 600mm in length but are sexually mature chinook salmon that return at an earlier age. One of seven Salmonidae species introduced into New Zealand. Supporting a large auaculture industry in New Zealand, Salmon is farmed in both ranch (releasing young to be caught later) and cage (rearing to market size) farms

NZ Marine Fishes: Paul