After the river flows into the sea, where do the large amount of freshwater fish go?

Freshwater fish will die in the sea and rivers will flow into the sea. Everyone knows that freshwater fish cannot live in salty seawater, so where did the freshwater fish go?

We all know that the reason why seawater is 'salty' is because the average salinity in seawater is 35‰, so we call seawater 'the homeland of salt land' . Compared to fresh water, the amount of salt contained in fresh water is only "thousand" 3/3" , completely incomparable. Seawater is completely undrinkable without treatment, the same goes for fish and freshwater fish cannot survive in the ocean.

The body structure of freshwater fish and saltwater fish is different. (Illustration).

There are many species of fish in nature. Based on their different habitats, humans divide them into two types: seawater fish and freshwater fish. These two types of fish cannot change their habitat. If a seawater fish lives in freshwater, it will die after two or three days, and the same is true for freshwater fish.

For example, humans drink processed fresh water every day, if we drink salt water every day, everything we eat will be salty, this is simply unacceptable for the human body. Fish live all day in fresh water, once they reach the sea, they will definitely be put in a 'pickle jar' , do you think fish can handle it?

Because the body structure of freshwater fish and seawater fish are different , and their living environments are also different, they cannot cross each other's living areas. So what should fish do if they are forced to leave their living environment under the influence of the outside world? Is death waiting?

Of course not.

Fish have a survival skill, which is migration. When fish feel they are being pushed out to sea and the surrounding salinity is higher, they will appear in a state of 'migration', which is often called 'fish in upstream water' . Freshwater fish tend to migrate upstream , when the situation has not become too bad, they will leave the dangerous place as soon as possible to survive.

Fish life is very diverse, currently in the world there are more than 36,000 known species of fish, of which about 8,600 are freshwater fish. Most fish species live in freshwater or marine water with less than 10% of fish migratory, moving back and forth between freshwater and marine habitats.

Growing in the sea but needing to reproduce in fresh water is called anadromous migration (such as the Chinese sturgeon), growing in fresh water but needing to reproduce in the sea is called downstream migration (such as the flower eel).

 As long as the fish is alive, it will migrate vigorously and try to swim back to fresh water. (Illustration photo).

If the migration of fattening and spawning occurs between rivers and lakes, it is called semi-migratory fish , generally fattening in lakes and spawning in rivers (such as the four major carp species). There are also some fish species that have a limited life in main rivers and tributaries and only migrate over relatively short distances.

That means, as long as the fish is alive, it will migrate vigorously and try to swim back to fresh water .

However, there are still a small number of fish that drift into the sea. They have a very strong ability to survive and do not die immediately because the salt content in seawater is not high. If they do not swim back to fresh water in time, they will die of edema.

Even if the river washes the freshwater fish out to sea every day, they will still feel the danger and swim around freely. Even if there is a strong current in front of them, and there is unpredictable danger, they will still try their best to swim back. In the end, most freshwater fish will return to freshwater , you don't have to worry.

There is also a type of freshwater fish called peripheral freshwater fish , which can live in both brackish water and sea water . Saltwater fish living in rivers occasionally enter, but the total number of these fish and animals is not large, only about a hundred species.