Facts About Fish Migration

There are a number of fish species that undertake migrations at some point of their lives. Fish migration may lead the fishes to travel fro distances ranging from a few hundred meters to thousands of kilometers over ocean waters. There are a number of reasons why fishes migrate.

Some fishes migrate across different water environments in order to find food or locate better feeding grounds. There are some fishes that feed on seasonal growth of plankton, a class of microscopic plants and animals that inhabit different bodies of water and an important food source.

Some fishes migrate in order to locate areas where plankton may be in abundance at certain periods of the year. Some larger fish species are also known to migrate by following other smaller plankton feeding prey.

There are also some fish species that are known to migrate in order to breed or spawn. These types of fishes may migrate to their spawning grounds during the breeding season which may be located hundreds of kilometers away.

The location may be at some great distance from the feeding grounds of the fish since the younger ones usually have different feeding requirements from the adult fishes. The spawning ground being far away from the feeding ground of the fishes also lessens the risk of the young being eaten by the adult fishes.

Migrating fishes are categorized by their different migration habits. There are oceanodromous fish species that migrate only within salt water only. There are also the potamodromous fishes that only migrate within fresh water environments.

Probably the most remarkable of migrating fish species seem to belong in the diadromous group which is composed of fishes that migrate from salt water to fresh water and back again.

Diadromous fishes are further divided into three types, depending on their life cycle. There is the andromous fish that live mostly at sea but breed in fresh water. The best known andromous fish is the salmon.

The salmon first spends its first days living in fresh water streams and move on to the sea where they live for several years. After they reach their breeding age, they return to the same freshwater stream where they were hatched and spawn the next generation of salmon their. After spawning, the salmon dies shortly thereafter.

There is also the catadromous fish that lives in fresh water and eventually migrate to salt water to breed. The most notable species known for this type of behavior are species of freshwater eels from the genus Anguilla.

As the eels hatch, they spend the first year of their lives living near estuaries where the sea meets with freshwater rivers. After becoming a year old, they travel upstream into freshwater rivers and stay there until they become adults.

The third type of diadromous fish belongs to the amphidromous type. These fishes move between fresh and salt water at some point of their lives but not for the purpose of breeding.