Chinook Salmon

Chinook are the largest Pacific salmon species, with some individuals known to grow to over 1.5 metres in length and weigh over 50 kilograms. They are distinguished by their small eyes and the small black spots covering their dark greenish-blue bodies, as well as the black gums of their lower jaw – hence the nickname “blackmouth.” The sides of their bodies are silver in colour and their bellies are white.

When spawning, their colour changes depending on a variety of biological and environmental factors. Both males and females can develop a deep red, copper, olive, brown or black color on their sides, although this tends to be more noticeable in males. Males can be easily identified by their hooked nose and ridged back, which also becomes most pronounced just before spawning. Young chinook salmon look very different from adults and have no spots on their bodies but instead 6-12 vertical lines that stretch from the top to bottom of their sides.

Travelling up to 4,800 km to spawn, Chinook salmon undergo incredibly long and strenuous migrations for reproduction. Fighting their way against the currents, they will travel to the rivers that they were born in using the sun as a compass and their sense of smell to find their way back. Two of the most important spawning rivers in Canada are the Yukon and Fraser rivers.

Once the fish arrive at the spawning location, the female will begin the process by digging a nest in the gravel with her tail. This nest is called a redd. Female Chinook are the most fertile (producing over 10,000 eggs per individual) and have the largest eggs of all Oncorhynchus species. Once the nest is ready, she will release her eggs. The males will time the release of their sperm to coincide with egg-laying to maximize the chance of fertilization.

Chinook salmon are known as semelparous species, meaning they reproduce only once before dying. Chinook salmon do not feed on the long trip to spawn, and the difficult task of swimming upriver, jumping up rapids and waterfalls, digging nests and reproducing, means their body condition continues to decrease throughout the spawning season. After spawning they die, their valuable nutrients returning to the rivers and coastal forest ecosystems to support productivity on land and in water.

The eggs will overwinter in the gravel of the river and hatch the following spring. After they hatch, baby Chinook salmon, called fry and parr, will either remain in the river for a year or more or begin the migration to the ocean within the first few months. This difference marks the salmon as “stream-type” or “ocean-type.” After making their way to the ocean, they will live and feed there until they reach maturity – and begin the cycle again. The young salmon can reach sexual maturity within two years of age but can wait up to eight years to return to the rivers to reproduce.

Chinook salmon are an important fishery species for many different groups. They are important to the commercial fishery, sport fisheries, Indigenous fisheries and aquaculture.

In 2015, the Chinook salmon commercial fishery was valued at $5.5 million. They are fished by trolling, seining and gillnetting. Though Chinook salmon are valuable, they are equally vulnerable; their populations have declined dramatically in recent years leading the government to implement fishery closures. They are also the preferred prey of the critically endangered Southern Resident orcas and as such, in 2018, Fisheries and Oceans Canada (DFO) reduced the total harvest of Chinook salmon by 25-35 per cent.

The future of the Chinook salmon fisheries are unknown. There have been broad declines in productivity of Chinook salmon across their range in recent years associated with large-scale environmental change and increased variability. However, there are many different stocks that migrate and spawn throughout the north Pacific Ocean and its rivers, and each one faces unique circumstances, making it complicated to evaluate factors affecting their abundance and survival. It also means that while some populations are already endangered, others are considered healthy, while still others are uncertain. Unfortunately, the unique challenges faced by each stock makes it difficult to understand the implications of different fishery management and conservation strategies.

Though they are native only to the north Pacific Ocean, Chinook salmon have been established, purposefully or accidentally, around the world – including the Great Lakes, New Zealand, Chile and other places. While many of the established populations are a result of escapement from aquaculture facilities, others have been successfully “transplanted” to new habitats. Chinook salmon are one of the most heavily cultured marine species and are the focus of an international farmed salmon market.

Understanding the status of Chinook salmon is difficult due to the many different stocks and unique challenges faced by each. From freshwater rivers to the open ocean, they can be hard to track and study. Some stocks even cross international borders throughout their lifecycle, thus making stock assessments and management an international effort.

Unfortunately, the issues facing the Chinook salmon are complex; overfishing, climate change, habitat destruction and alteration all threaten Chinook salmon, and several populations are critically endangered or even extinct. Dams that prevent this species from reaching its preferred spawning grounds are one of the most detrimental human impacts on Chinook salmon populations.

In Canada, the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) has listed the Okanagan population of Chinook salmon as Threatened. Both geographically and genetically distinct, they are the only population of Chinook salmon in the Columbia River Basin in Canada. Habitat destruction due to dam construction and overfishing are two of the main factors that have led to this stock’s decline. From 2013-2017, the number of mature salmon from this stock was frighteningly low, only ranging from 19-112 individuals.

In 2016, Fisheries and Oceans Canada classified about a third (11) of Chinook salmon conservation units in southern British Columbia (35) as in the red zone, meaning they need to immediately consider ways to protect these fish and increase their abundance. Fortunately, Chinook salmon protection and conservation remains a topic of high regard for both government and non-government agencies.

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