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Pacific salmon is naturally occurring in the North Pacific Ocean, the Bering Sea, the southern Arctic Ocean and surrounding fresh water.

Did you know?

Many salmon are anadromous — this means they live in the saltwater of the ocean but return to freshwater to spawn.

Scientific name: Oncorhynchus (5 Pacific salmon species in North America)
Average weight: 1 kg–18 kg
Average length: 50 cm–90 cm
Average lifespan: 2–5 years
A pair of Pacific salmon swimming in British Columbia

About

Biology

Under the Oncorhynchus genus there are seven species of salmon, five of which are found in Canada (the other two in Asia). The Canadian species range widely in size and weight. Pink and sockeye tend to be at the smaller end of the scale (1kg–3kg) and chinook at the larger end (6kg–18kg), with chum and coho generally the same size, in the middle range (4kg–7kg). Rainbow and cutthroat trout are also in the genus but generally not anadromous.

While Pacific salmon have teeth in their jaws, the genus name Oncorhynchus refers to the hooded snout commonly seen on most spawning males — a hook-like structure called a kype which develops on its jaw prior to reproduction. Conversely, the female’s head remains streamlined throughout her lifetime. In general, the Pacific salmon has a short dorsal (top) fin followed by a fatty (adipose) fin on the back near the tail. As an adult living in the ocean, the salmon typically has a dark blue-black or blue-green back with some having black spots there as well and silver sides and bellies. Also on the belly is a large anal fin ray, directly under the adipose fin.

Flesh of salmon varies among the five species ranging from white (chinook) to pink to red, with sockeye and coho having the brightest colours.

Habitat and behaviour

The habitat of a salmon generally alternates between the freshwater stream or lake — where it was hatched — to the ocean water, where it swims for the duration of its life returning to its specific freshwater origins to reproduce.

The life cycles of the five Pacific salmon vary to a degree but some generalizations can be made. In the spring, summer and fall, the Canadian species migrate into rivers, streams and lakes, and all will spawn in the late summer or fall, regardless of when they arrived, usually when the water temperature falls below 16˚C. Courtship occurs, eggs are released (2,500 to 7,500 depending on the species), fertilized and buried.

The burial site is crater-like and called a redd, with the size of the gravel chosen for it depending on the size of the female. Each female digs one redd. There tends to be four or five nests of 500 to 1,200 eggs apiece within each redd. The eggs will hatch into a non-feeding larval form (alevin) by mid-winter, however they will never see their parents as the adults die after spawning. In the spring, the young (fry) emerge and either migrate directly to sea (pink and chum) or go to a nearby freshwater nursery (all others) for up to two years. All of these five species of Pacific salmon eventually make their way to the ocean.

The Pacific salmon is impressive for several characteristics including its vast migration distance of, at times, thousands of kilometres, with chum undertaking the greatest migrations and pink and coho the shortest. Another impressive feat is the salmon’s ability (excluding chum and pink) to jump two metres vertically, ascending rapids, on its return home to spawn.

Juvenile salmon in freshwater commonly eat zooplankton as well as larval or adult insects. In the ocean, the salmon diet consists of various zooplankton, smaller fish (herring, sand lance), squid, amphipods (tiny shrimp-like crustaceans) and krill. In general, however the Pacific salmon is a very opportunistic eater.

Range

The Pacific salmon is naturally occurring in the North Pacific Ocean, the Bering Sea through the Bering Strait, the southern Arctic Ocean and surrounding fresh water. Within British Colombia, it is found in close to 1,500 rivers and streams, most notably the Skeena River, the Nass River and the Fraser River. Some have been observed as far north as the Northwest Territories’ Mackenzie River. As well, it is commonly raised by humans on aquatic farms and has been exported worldwide and now thrives in places as far away as New Zealand.