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The journey of the Chinook salmon is dangerous. When the fish first come out of their eggs, they are tiny, barely an inch long. They remain in their stream for about a year as they grow larger.
Many animals hunt the salmon for food in the stream and as they begin their migration down the river. The salmon can become meals for larger fish, birds, and land animals such as bears.
The salmon that survive the journey to the ocean grow large there. Then, they must begin their journey back, swimming upstream against the current. They face predators on this journey as well. A predator is an animal that eats other animals. Animals that get eaten by other animals are called prey.
Damming the River
Another danger facing the salmon is that people have changed the natural flow of the river. This is done with dams. A dam is a special kind of wall that holds back water. Dams slow down the flow of a stream or a river. Because of this, people use dams to control flooding.
They also cause water to pool behind them. This creates a new pond or lake called a reservoir.
How Dams Help People
People also use dams for electricity. Most of the electricity in the northwest United States comes from dams on the rivers. Electricity that comes from moving water is called hydroelectric power. Hydroelectric power is a renewable energy source because it can be replenished in a short period of time.
Remember that moving water has kinetic energy. In a dam, that moving water turns turbines. Those turbines then turn a metal shaft in an electric generator, which is a motor that produces electricity. People use electricity to power lights, electronics, and other appliances.
Protecting Salmon
When fish reach the reservoir of a dam, the river current stops. Without the flow of water, the fish become confused because they lose their sense of direction.
Dams can also be deadly. If a fish is swept into the turning blades of a turbine, it can be killed.
Many commercial fishermen value Chinook salmon and want to help protect the fish. So engineers have designed different technologies to protect the salmon. Most of these technologies, like fish ladders, help the salmon move past the dam so they can continue their journey to the ocean.
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