Chinook Salmon (Oncorhynchus tshawytscha)

Chinook salmon are the largest Pacific salmon species and, on average, grow to be three feet (0.9 meters) long and approximately 30 pounds (13 kilograms). However, some Chinook salmon can reach more than five feet (1.5 meters) long and 110 pounds (50 kilograms).

The salmon are blue-green on the head and back and silver on the sides. The fish’s tail, back, and upper fin have irregular black spots, and black markings also are present around the gums. Male Chinook salmon have a distinctive hooked nose at the top of the mouth and a ridged back. During the mating season, both male and female salmon develop a reddish tint around their back fins and tail.

These salmon utilize many different habitats throughout their lives. Adults lay eggs in fast-moving freshwater streams and rivers. Juvenile salmon spend some time in the freshwater streams before moving to estuaries with a mix of freshwater and saltwater. As the salmon reach adulthood, they move out into the open ocean.

Young Chinook salmon like to eat insects and small crustaceans, particularly amphipods. Adult salmon dine mostly on other fish. 

Chinook salmon are anadromous, which means they are born in freshwater streams and travel to the open ocean to grow into adulthood. For the first year or so, the juvenile salmon stays in its freshwater habitat. Then it moves to estuaries and on to the open ocean, which provide a lot of food and nutrients to the developing salmon.

When an adult Chinook salmon reaches maturity, which can be anywhere from three to seven years of age, it makes the long migratory journey back to the site of its birth stream to produce young. After so many years, some salmon can be hundreds of miles away. At their birth stream, male and female salmon pair up to breed. The time of breeding depends on the river and the population of salmon, but most breed in the summer and autumn. A female digs a nesting hole (called a redd), where she deposits thousands of eggs before the male releases his sperm. After mating, the male and female stand guard over the eggs to protect them from predators. Chinook salmon burn a lot of energy migrating to the nesting grounds, breeding and protecting the eggs. Both parents will die before the eggs even hatch.

Some populations of Chinook salmon are federally listed as endangered, while others are listed as threatened. They are endangered in the Columbia River tributaries and California breeding sites and threatened in a range of rivers and streams throughout Oregon, Idaho, and Washington. Threats to Chinook salmon including overfishing, overuse of water resources, development, and habitat loss. Dams also pose a threat if the speed of water flow is altered or access to natal streams is blocked. 

The Chinook salmon is an important keystone species of the Pacific Northwest. It is a vital food source for a diversity of wildlife, including orcas, bears, seals, and large birds of prey. Chinook salmon are also prized by people who harvest salmon both commercially and for sport.