lautnusantara.com - Have you ever heard about anadromous anad catadromous fish? These are term that used to describe particular fish that has migratory pattern. 

Anadromous

Anadromous fish is a fish that spend most of their live in the saltwater or sea and will return to the freshwater to spawn. after the eggs are hatch, the juvenile will stay in freshwater for a while and at some points their young would go back to the sea to undergo maturation. The adults fish will eventually back to freshwater when it is time to spawn. Some species of fish would travel more than hundreds of kilometres between their breeding ground and their marine habitat. Other species just migrate a few distance to spawn in to the brackish water. The term ‘anadromous’ generally means upward-running. 

Some species of fish that categorized as anadromous fish are striped bass, salmon, steelhead trout, sturgeon, smelt, shad and herring.

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Catadromous 

Catadromous fish is a fish that live most of their lives in the freshwater and will return to the saltwater to spawn. Catadromous fish eggs will hatch and experiencing juvenile period in the seawater. Their young will migrate to freshwater in order to undergo the maturation. Catadromous fish will spend most of their life in freshwater. The term ‘catadromous’ is generally means downward-running.

The main type of catadromous fish is true eels, which their females will spend most of their life in freshwater. The males usually tend to live in the brackish water. 

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Why do Fish Migrate?

There are three main reasons why fish do the migration, spawning cycles, food availability, and environmental condition.

The main reason for fish migratory patterns can be linked to their spawning seasons, also known as the reproductive pattern of migration. Migration also offers a chance for species to converge at same location which helps to make sure the success of their reproduction. The other reason is fish migrate to locate the better feeding ground. Migration can decrease the competition for food between adults and young by placing them in separate ecosystems. 

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