Page background

Salmon

About AquaFacts: AquaFacts are a resource for students who are looking for information on the animals at the Aquarium or other Aquarium-related topics. Here, we’ve compiled some of the most frequently asked questions that we’ve received about salmon. The answers come from our biologists and from reputable sources that we reference at the end of this page. If you have a question about salmon that’s not addressed in this page or the references below, please feel free to email our librarian.

Salmon

Questions & Answers

What makes a Pacific salmon a Pacific Salmon?

Most Pacific salmon are anadromous: they are born in fresh water, spend their adult lives in the saltwater oceans and return to their natal rivers, or lakes, to spawn. They are also semelparous, meaning they die after they spawn. Atlantic salmon, Salmo salar, are anadromous but may spawn more than once.

How many species of Pacific salmon are there?

There are seven species of Pacific salmon, plus two freshwater species.

  • Five species are found in B.C. waters: sockeye, Oncorhynchus nerka; pink, Oncorhynchus gorbuscha; chum, Oncorhynchus keta; coho, Oncorhynchus kisutch; and chinook, Oncorhynchus tshawytscha
  • Two species of Pacific salmon, masu, Oncorhynchus masou, and amago, Oncorhynchus rhodurus, are only found in Asian waters
  • The rainbow trout, steelhead and cutthroat, are part of the Oncorhynchus genus, but are primarily freshwater fish

salmon-chinook.jpgsalmon-coho.jpgsalmon-sockeye.jpg

What are the stages of a salmon's life cycle?

There are six stages of a salmon's life cycle: eggs, alevin, fry, smolt, adult, and spawners.

The salmon life cycle begins, and ends, as the spawning process in fresh water. The female chooses a site for her nest(s), called a redd, and builds one to several nests in the gravel with her tail. She then deposits her eggs into the nest and one or more males fertilize the eggs. The female then covers the eggs with gravel and repeats the process. Adult salmon guard the redd site until their death.

In late winter, eggs hatch from the redds. Young alevin in the gravel live off the nutritious yolk sac that hangs off their undersides for up to four months. Then they swim up from the gravel to start feeding on live prey. Some species head straight to the ocean as fry, while others remain in the stream for another year.

Next, the smolt stage occurs. The juvenile salmon swim downstream and undergo major physiological changes (smolting) while adapting to salt water in estuaries, where freshwater rivers meet the saltwater seas. Once in the ocean, Pacific salmon migrate to the North Pacific Ocean, travelling in schools. After one to seven years, depending on the type of salmon, they return to their home rivers to spawn where they had hatched.

What physical changes occur with spawning salmon?

Physical changes vary between the species of salmon and are dependent on the amount of time between a salmon's entry into fresh water and spawning. The sleek and silvery body maintains its shape, but the female swells in the abdominal area and her snout slightly elongates. The male develops a prominent fleshy hump by the dorsal fin, the snout becomes longer and hooked, and the upper jaw elongates. Colour changes occur but they differ between species. For example, the backs of the sockeye salmon change to a brilliant, red colour.

How many eggs do salmon lay?

Female salmon carry 2,500 to 7,500 eggs, depending on the species and size of the individual salmon. Each nest has between 500 and 1,200 eggs, and each female salmon has four or five nests.

Which B.C. rivers are salmon commonly found in?

Salmon are common in most B.C. rivers, but the largest runs occur in the Fraser, Skeena, Nass, Somass, Thompson and Adams rivers.

How do salmon protect themselves?

When migrating, salmon are particularly susceptible to predation, so they seek deep areas to quickly swim into. Salmon school in the ocean for protection, and confuse predators with their flashy sides where they can be mistaken for a large predator.

How are salmon commercially fished?

There are three common techniques for commercial fishing: seining, gill netting and trolling. Seining involves setting nets to encircle schools of fish. Once a catch is made, the net is drawn up and brought aboard. Gill netting involves dropping a large nylon net in the ocean like a mesh wall, with orange bobs to keep it afloat, and then scooping up the catch. Trolling involves dragging a series of lines and baited hooks that are attached to long poles that extend from the boat.

Are salmon endangered?

Our lifestyles have strong and often negative impacts on salmon stocks. Overfishing has led to a decline in salmon stocks. We develop land that destroys habitats and build dams that divert salmon runs in order to generate electricity. All of these development methods have led to a decline in salmon populations.

What is the cultural significance of salmon to First Nations' communities?

Salmon are at the base of many First Nations culture. There are songs, dances, visual arts and legends based on the lives of salmon. First Nations of B.C., including Bella Coola, Nootka, Tlingit and others, have relied on salmon as a primary source of subsistence before the salmon populations began declining.

What are farm salmon?

Farm salmon are raised for market in large undersea cages, or net pens, off the B.C. coast. Some escaped salmon, including Atlantic salmon, are able to find spawning areas. Atlantic salmon are the most commonly farmed salmon because they have better growth and survival rates on farms than the Pacific salmon. Chinook and Coho are also raised in B.C. Salmon aquaculture is the name given to raising farm salmon. They are hand-fed fishmeal pellets (a vitamin rich, high-protein diet), for about two and a half years, until they are harvested.

What animals eat salmon in the rivers and oceans?

There are diverse predators of salmon at the varying stages of their lives. Other fishes, members of their own species, snakes and birds eat salmon fry. Once in the ocean, salmon are prey to whales, dolphins, seals, sea lions, other fishes and, of course, humans. Bears and birds often scoop up spawning salmon.

What do salmon eat?

A salmon's diet depends on the species and region, but typically juvenile salmon eat zooplankton, and larval and adult invertebrates. In the ocean, salmon eat smaller fish, such as herring, pelagic amphipods and krill.

What is the BC Hydro Salmon Stream Project in Stanley Park?

The BC Hydro Salmon Stream Project in Stanley Park is a community project supported by BC Hydro, the Vancouver Park Board and the Vancouver Aquarium Marine Science Centre to provide the public with an opportunity to witness a salmon run. The demonstration stream began development in the fall of 1999, winding its way from the Aquarium through to Coal Harbour, near the Vancouver Rowing Club. In the summer of 1998, 10,000 hatchery-bred Chinook and Coho salmon fry were released in Coal Harbour. A pheromone was released into the water to help the mature salmon to "scent" their way to their home stream in the year 2000.



Facts & References

Did You Know?

  • Pheromones, or chemical cues in the water guide salmon allowing them to find their birth streams
  • The genus Oncorhynchus dates from at least the Pliocene era, six million years ago
  • When spawning, salmon are capable of vertical leaps more than two metres
  • Chinook are known to travel more than 16,000 km in the Pacific Ocean before they return to spawn
  • Less than two percent of salmon hatched in redds will return to spawn
  • Fish ladders are made to provide upstream passage for salmon over a dam or natural barrier that affects the advancement to spawning grounds

References

  1. Groot, C. and L. Margolis. 1991. Pacific Salmon Life Histories. Vancouver, UBC Press.

Permission is granted by the Vancouver Aquarium Marine Science Centre for classroom teachers to make copies for non-commercial use. This permission does not extend to copying for promotional purposes, creating new collective works, or resale.

Jellyfish

Share Your Thoughts

How was your visit? Fill in our comment card and let us know.
Find it here

The Big Reveal

The Big Reveal

Come celebrate the biggest expansion in our history!
Learn more

Did You Know?

Did You Know?

Sea otters hold hands to rest in groups called “rafts”.
Read more