Atlantic salmon

The Atlantic salmon is a big fish.

They live in cold rivers and the ocean. Most start in small streams. They grow up and move to the sea.

In the sea, they eat small fish. This helps them grow very large. They can even return to the sea to lay eggs again.

Some salmon stay in lakes. They spend their whole lives in fresh water. These are called landlocked salmon.

People catch them for food. We must work to keep their homes safe.

The Atlantic salmon is a large fish.

Most of these fish live in the ocean and rivers. This way of living is called anadromous. This means they hatch in fresh rivers. Then they move to the salty sea to grow. Later, the adults swim back up rivers to spawn, which means they lay eggs.

Young salmon go through many stages. First, they are alevin. They stay near the eggs and use a yolk sac for food. Next, they are fry. They leave the breeding area to find food. Then they become parr. These fish have blue and red spots. Finally, they become smolt. They turn silver to hide in the sea.

Some salmon are landlocked. This means they stay in lakes their whole lives. Atlantic salmon are very tasty. People catch them for food. This can hurt their numbers. People also build things like dams that block their path. Many countries now work to protect them.

The Atlantic salmon is a large and impressive fish.

It belongs to a family of fish called Salmonidae. This species is the third largest in its family. It lives in the northern Atlantic Ocean and in rivers. Most of these fish follow a special way of living. This way of living is called anadromous. It means they hatch in fresh rivers but grow in the sea.

Life for a salmon happens in several clear steps. First, they hatch as tiny alevin with a yolk sac for food. Next, they become fry and start hunting for tiny creatures. After that, they grow into parr with blue and red spots. To get ready for the ocean, they become smolt. During this time, they change their color to shiny silver.

This helps them hide in the sea. Finally, they swim out to the ocean to find food and grow large.

Scientists have studied these fish for a very long time. A Swedish zoologist named Carl Linnaeus named them in 1758. He used the scientific name Salmo salar. This name might mean "resident of salt water."

The fish can be quite large after living at sea. One salmon caught in Scotland in 1960 was the heaviest ever recorded. Another salmon caught in Norway in 1925 was the longest on record.

Atlantic salmon live in many different places around the world. They are found in Europe and the northeastern coast of North America. In Europe, they live from Spain to Russia.

Some salmon are landlocked and stay in lakes their whole lives. This happens in places like Lake Ontario. In the ocean, they use sea currents to travel. They can even sense the Earth's magnetic field to help them find their way. This helps them return to the exact river where they were born.

These fish are very important to many people and animals. People enjoy eating salmon because it is very nutritious.

Because they are tasty, people fish for them for food or sport. This can make it hard for some salmon populations to grow. Some people also farm salmon in large cages to help provide food.

This farming is very common in Norway. Protecting the rivers where they live is a big job for many countries.

The Atlantic salmon, known scientifically as *Salmo salar*, is a large ray-finned fish.

It belongs to the family Salmonidae. This species is the third largest in its family, following the Siberian taimen and the Pacific Chinook salmon. Most populations are anadromous, which means they hatch in freshwater rivers but migrate to the ocean to mature.

However, some populations are landlocked. These fish spend their entire lives in freshwater lakes and rivers. This variety allows the species to inhabit many different environments across the Northern Hemisphere.

The life cycle of the Atlantic salmon involves several distinct biological stages. It begins as an alevin, a tiny fish that stays in the breeding grounds. Alevins use nutrients from a yolk sac to grow and develop their gills. Once the sac is absorbed, they become fry and begin hunting for small invertebrates. As they grow, they enter the parr stage, characterized by blue and red spots for camouflage. To prepare for the ocean, they undergo smoltification. This is a process where they develop a silver-blue sheen and undergo endocrinological changes. These changes help their bodies adapt to the salt in seawater. Once they are smolt, they begin swimming with the current toward the sea.

Life in the ocean provides the salmon with opportunities for massive growth. In the sea, they feed on plankton and small fish like herring or capelin.

They do not swim thousands of kilometers across the open ocean. Instead, they use sea surface currents to travel. They can navigate using the Earth's magnetic field by sensing it through iron in their lateral line. This helps them return to their natal rivers to spawn. Most salmon return to the same river where they were born, though about 5% go to the wrong river.

Atlantic salmon are iteroparous, which is a special trait compared to Pacific salmon. This means they can survive the spawning process and return to the sea to spawn again in a later year. About 5% to 10% of adults successfully return to the ocean to repeat the cycle. These repeat spawners can grow to extremely large sizes. In 1925, a salmon caught in Norway set the record for the longest Atlantic salmon ever recorded. In 1960, a salmon caught in Scotland became the heaviest recorded in scientific literature.

Humans have interacted with these fish for centuries. The Swedish zoologist Carl Linnaeus gave the species its scientific name in 1758. The name *Salmo salar* likely means "resident of salt water." Because salmon meat is highly nutritious, it is a prized food in many cultures.

This popularity has led to intense commercial and recreational fishing. Historically, European settlement in North America caused salmon populations to decline. Activities like timber harvesting, dam construction, and agriculture destroyed many freshwater habitats. By 1850, more than half of the historical salmon runs in North America had been lost.

To address these declines, many countries have started conservation efforts. These programs aim to protect the rivers and habitats the fish need to survive.

Another major development is aquaculture, which is the farming of fish. Many countries now farm Atlantic salmon in large numbers to provide food. Norway is a leader in this industry, producing over 50% of the world's farmed supply.

While farming is a viable alternative to wild fishing, some environmentalists criticize these methods. They worry about how large-scale farming might impact the natural environment.

Understanding the Atlantic salmon requires looking at the connection between water temperature and survival. They are cold-water fish and are very sensitive to changes in temperature. As the climate warms, some populations have moved north, such as those colonizing Svalbard between 2002 and 2006. The survival of the species depends on the health of both the freshwater rivers and the saltwater currents. By studying their migration and biology, scientists work to balance human needs with the survival of this remarkable species.