Salmon swim upstream to mate and lay their eggs for several reasons. Laying their eggs in small rivers and shallow waters help protect them from larger fish that would happily eat them as a snack in the ocean. The shallow streams and rivers also provide shelter for the eggs so they don’t get washed away by heavy currents .
Why do salmon swim upstream to spawn?
The main reason salmon swim upstream is to ensure the survival of their offspring. This fish spawning habit is what leads to the salmon passing down their genes successfully.
Do salmon lay eggs in streams?
If a salmon laid their eggs in the ocean, they would be swept out to sea or eaten by the thousands of other fish species they live with. Smaller rivers and streams don’t have these perils. Streams have weak currents and not many predators that eat salmon eggs.
Salmon return to rivers from the ocean and swim upstream to their original hatching place to lay and fertilize their eggs. Swimming upstream is hard work, and only the strongest complete the journey and spawn the next generation of salmon.
Does salmon really swim upstream?
Salmon and other fish swim upstream because they must make the journey for reproductive purposes. Salmon and a number of other fish, including coho and rainbow trout, follow a familiar scent that leads them back to the location of their birth.
Salmon are known to scientists as a keystone species because their journey upstream made only $1 billion available initially. Oregon has more than 40,000 barriers blocking fish passage.
The migrating salmon need cool and well-oxygenated water simply to be able to make the entire journey upstream and once the eggs are laid (usually in gravel beds), their continued survival heavily depends on the presence of oxygen in the water. Yet another reason for the salmon to swim high up the rivers is security.
Do salmon swim up stream against the currents?
The run up the river can be exhausting, sometimes requiring the salmon to battle hundreds of miles upstream against strong currents and rapids. They cease feeding during the run.  Chinook and sockeye salmon from central Idaho must travel 900 miles (1,400 km) and climb nearly 7,000 feet (2,100 m) before they are ready to spawn.