The sockeye salmon (Oncorhynchus nerka) is a small, color changing salmon found in the northern Pacific Ocean. Like other salmon, sockeyes are anadromous, meaning they live in both fresh and saltwater. They are born in freshwater, and migrate to the ocean as young adults. Only to embark on a treacherous journey back to their birthplace to spawn, and die.
1. Red salmon are born silver, then turn blue when they go to the ocean. They turn red when they return to freshwater
Despite the nickname red salmon, these fish are not red for most of their lives. The alevins and fry are actually silver. As they quickly grow, they become blue with a silver tinge and small black specks along their backs. Hence the other nickname, blueback salmon. Bluebacks begin turning red when they reenter freshwater as adults. By the time they reach their spawning sites, they will be vibrant red with green heads.
When male sockeyes reach sexual maturity, they develop a hooked jaw and humpback
All sockeyes develop the famous red and green coloring. But males go through extra changes. Male sockeyes develop a hooked upper jaw, with small but sharp teeth. They also develop a dorsal hump. This humpback grows as they reach maturity. Studies have shown that females tend to select males with larger humps to fertilize their eggs.
2. With no mother to feed them, sockeye alevin eat their yolk sacs until they develop into fry
Sockeye eggs hatch between six and nine weeks after mating. Since parents die shortly after mating, the alevin have to take care of themselves. The larvae, called alevins, eat their yolk sacs for the first few weeks of their lives. These babies develop into fry. Fry are very tiny, but emerge from the gravel to feed on zooplankton. As fry eat, they grow quickly into juveniles.
3. Blueback salmon feed on zooplankton in large schools to avoid predators
Unlike other pacific salmon, blueback salmon eat zooplankton as adults. They are selective about what they eat. The school’s movements are fast and graceful. The salmon can change position in an instant. They prefer vertical movements. Salmon in a school will change positions in columns as they eat to avoid being eaten. In the Pacific Ocean, sharks and whales, especially orcas, prey on salmon.
4. After 1-3 years in freshwater, the salmon will migrate over 1000 miles to the Pacific Ocean
Juvenile bluebacks spend the first 1-3 years of their lives in freshwater. Then, they will journey up to 1000 miles (1600 kilometers) through rivers and streams to reach the Pacific Ocean. They make this long journey because they are outgrowing their habitat. The ocean is vast and full of higher quality food. This allows sockeyes to grow and reach maturity.
Kokanee salmon are sockeyes that spend their entire lives in freshwater
Some sockeye salmon populations spend their whole lives in freshwater. These are called kokanee salmon. Scientists believe that modern kokanees are the descendents of sockeyes that stayed in freshwater when an ice cap melted 15,000 years ago, providing outlets to the sea. When sockeye salmon reach their mating grounds, they do not reproduce with the kokanees already there.
5. Blueback salmon use their strong sense of smell to migrate back to their freshwater birthplace for spawning
Blueback salmon have an incredible sense of smell. In fact, they use scent to guide them back to the freshwater habitat where they were born. Salmon can smell a chemical down to one part per million. Salmon don’t remember the route they took to the ocean. But they follow the faint traces of their pheromones (animal scent particles) until they reach their birthsite.
Smaller sockeye have a lower mortality rate during migration because of shallow waters and predators that target larger fish
Smaller sockeye have an advantage during their migration back to freshwater. Their journey covers over 1000 miles, and there’s a lot of danger along the way. Larger salmon have a higher mortality rate during migration for two reasons.
- Shallow/obstructed water ways. Larger salmon are more likely to get trapped swimming in narrow or shallow waterways. If the water is very shallow, a big sockeye won’t be able to stay underwater. These fish will suffocate. But smaller sockeyes can slip between rocks and keep their heads under water.
- Predators: Sockeye salmon migrate to their spawning site in fall. In fall, many animals are preparing for their winter hibernation. Bears, eagles, and wolves all prey on sockeyes migrating through freshwater. And these large animals need to eat as much as possible to survive the winter. They target the larger sockeyes, which are easier to notice and catch.
6. Sockeye salmon die after mating once
Sockeye salmon only spawn once in their lives, and die shortly after. This makes them semelparous. Animals that are semelparous put all their energy into maximizing reproduction. So when sockeyes return to their freshwater habitats, they focus all their energy on laying or fertilizing as many eggs as possible. Females spend the last few weeks of their lives protecting their eggs.
Sockeyes stop eating when they reach their spawning site
When sockeyes reach their spawning site, they stop eating. And lakes and streams are filled with fish and zooplankton for them to eat. One reason might be because of how they feed. Sockeye salmon swim and feed in large schools. When they reach their spawning sites, they become competitive. The salmon fight each other for dominance, and do not cooperate enough to eat. They also have less predators to worry about.
7. One Female sockeye will lay 2,000-5,000 eggs per redd, but only 1 in 1000 will survive to become a fry
Sockeyes are small for Pacific salmon, but not as tiny as many egg laying species. Female sockeye dig little ruts in the gravel in shallow water. These ruts are called redds. After several days of digging, the ladies lay 2000-5000 eggs in each redd. A single female can lay up to 10,000 eggs. But only 1% of the fertilized eggs will survive to hatch into fry. So it’s very important that females lay as many eggs as they can.
8. Sockeyes form hierarchies that favor the larger salmon
During mating, sockeye form hierarchies. The salmon challenge each other for dominance. Larger fish have the advantage here. A non dominant male will have to be sneaky to reproduce. After a female lays eggs, he will sneak into the redd to release his sperm. Males prefer larger females because they carry more eggs. Females also use their larger tail fins to dig deeper redds, better protecting the eggs.
After laying eggs, females have to protect their redds from other females
Male sockeyes release their sperm over a redd and move onto the next. But females only lay eggs once. Mothers spend the last few weeks of their lives protecting their eggs. The mom-to-bes aren’t always protecting the eggs from predators. They protect them from other female sockeyes. Two females will fight until one dies or swims away. This is another reason why male sockeyes prefer larger mates.
9. When sockeyes die, they are either eaten or release nutrients into water as they decompose
Sockeye salmon are keystone species. This means that their environment really depends on them. When sockeyes die after spawning, other animals eat their carcesses. These dead salmon are a nutritious, easy meal for hungry animals in the spring. Sockeyes that aren’t eaten decompose. As the bodies break down, they release nutrients into the water.
Sakae? Sucky? Sockeye? Eh, close enough
There’s nothing special about the sockeye salmon’s eyes, so why the nickname? Sockeye is actually sθə́qəy̓, which is the Halkomelem word for “red fish.” Halkomelem is a language that indigenous peoples living in what is now British Columbia spoke. When the first English settlers arrived, they couldn’t pronounce sθə́qəy̓. So they called the fish sockeye. For the record, it's pronounced suk-kegh. Say it out loud a few times. Do you think it’s really hard to say?
How endangered is this animal?
- The IUCN lists the sockeye salmon as Least Concern
- America’s National Marine Fisheries Service lists the sockeye populations in the Snake River and Lake Ozette as “threatened”
- Commercial overfishing has led to dramatic declines in sockeye populations around the Pacific Northwest.
The salmons are mass fished to be sold in restaurants and grocery stores
- Abandoned dams and urban sprawl block many sockeyes from reaching spawning sites.
Also Known As
Red salmon, Kokanee salmon, or Blueback salmon
Up to 33 inches (84 cm)
North America, West Coast, Pacific Ocean
Rivers, lakes, and coastal seas
Zooplankton, small crustaceans, small fish
3 to 5 years