Chinook Salmon (Oncorhynchus tshawytscha)

This species is part of the family Salmonidae, which includes the salmon, trout, char, whitefishes and grayling. Chinook salmon are a Pacific salmonid with a native range of western North America, eastern Russia and Japan. Chinooks have also been the subject of numerous introductions around the world (Such as Mexico, Argentina, Chile, Nicaragua, England, Ireland, Holland, France, Germany, Italy, Australia and New Zealand). A notable introduction has been to the Great Lakes where chinooks were introduced to control an overpopulation of alewife. Many of the Great Lakes populations are not believed to be self-sustaining although recent data has suggested that certain populations have become naturalized.

Chinook salmon are anadromous, that is they hatch in freshwater rivers, migrate to the ocean (or large lake) to feed and mature and return to the same river to spawn. Like all Pacific salmon, chinook salmon die after their first spawn. Large changes in male body shape and coloration take place prior to spawning. Most males develop a hooked-jaw (known as a "kype") and either red or black coloration (West-coast males often turn red while Great Lakes males turn black). Spawning runs vary depending on location with summer and fall being the prevalent spawning seasons. The distance traveled upstream can vary from a few hundred yards to 1200 miles.

Spawning habitat and behaviour is fairly constant across the species range. Chinooks spawn in riffles with gravelly bottoms. Spawning behaviour involves females excavating a nest (properly termed a "redd") by turning on her side and fanning her tail to create a depression in the gravel. Males compete with one another in an effort to win spawning rites. Typically the largest males are successful in contests with other males and thus are the successful spawners although smaller males also succeed by sneaking onto the redd and depositing their sperm (click here for more information on sneaker males). Following spawning, the female attempts to cover up the redd with gravel in much the same way as she created it (by fanning out an area upstream from the actual redd). The eggs hatch the following spring. Young remain in the stream for between a few months and 2 years depending on the river. As the parr (young salmon) move downstream they prepare to make the transition to saltwater. This process, known as smoltification, is a remarkable physiological feat whereby the salmon alters the processes that deal with salt in its body.

There is some variation in growth among populations although typically salmon live between 2 and 9 years. Salmon typically spend 2-3 years in the ocean or lake. Chinook salmon are the largest of the Pacific salmonids and can reach weights of 120 pounds (in Alaska). Chinook salmon grow quickly once in the ocean (or lake). Upon reaching saltwater, smolts weigh at best half a pound. Returning a few years later they have put on between 10 and 120 pounds. Young freshwater chinooks feed on aquatic and terrestrial insects. Once smolts go to sea they continue to feed on aquatic invertebrates although at a certain size they switch over to primarily a fish diet. Adult salmon continue to eat shrimp, squid and crab larvae however, needlefish, herring and capelin make up a higher proportion of the diet. In the Great Lakes, adult chinooks feed primarily on alewife and smelt.

Chinook salmon are touted as a fantastic sport and table fish. Their large size and hard fighting abilities makes them a popular choice for anglers both in saltwater and freshwater. Their flesh varies between bright red and white although both are highly valued served fresh, raw or smoked. However, the quality of the meat deteriorates as spawning nears since all of the salmon's energy is devoted to reproduction. A large commercial harvest exists in the Pacific Ocean while aboriginal spearing and seining takes place in spawning rivers.