Migration in Fishes
Many fishes migrate on regular basis, on a time scale ranging from daily to annually or longer. It may be of short distance over a few meters to thousands of kilometers.
Reason for Migration in Fishes: Fishes usually migrate to feed, to reproduce, or in some cases the reason is not known. Most fishes migrate to reproduce, as some live in seawater but reproduce in fresh water and vice-versa.
Classification of Migration in Fishes:
The types of migratory fishes are as follows:
Anadromous fishes migrate from the sea up into freshwater to spawn, examples – salmon, striped bass
- These fishes spend most of their lives living and feeding in the sea.
- Salmon and striped bass are well-known Anadromous fishes, that make large migrations. Salmon spawn in the cold, clear waters of lakes or upper streams. They lay eggs in gravel beds.
- Salmon stops feeding during the journey and changes its body colour from silver to reddish-brown.
Catadromous fishes migrate from fresh water down into the sea to spawn. Freshwater Eels (A. anguilla) are catadromous fishes. They spend most of their lives in freshwater.
- During the journey, the eel changes colour of the body from yellow to metallic silver grey.
fish that live and migrate wholly in the sea. These occur widely throughout the world’s oceans.
Examples- Herring (Clupea harengus), Cod (Gadus morhua), Tuna
George S. Myers coined the inclusive term diadromous to refer to all fish that migrate between the sea and freshwater
fish that migrate from freshwater to the seas, or vice versa, but not for the purpose of breeding
fish whose migrations occur wholly within freshwater.
Examples- Carp, Catfish
Some other movements also fund in fishes like-
- George S. Myers coined the inclusive term diadromous to refer to all fish that migrate between the sea and freshwater
- Some fish such as tuna move to the north and south at different times of the year following temperature gradients.
- Altitudinal migration
- The bull shark is aneuryhaline species that move at will from fresh to salt water, and much marine fish make a diel vertical migration, rising to the surface to feed at night and sinking to lower layers of the ocean by day.
- Freshwater movement of fishes also occurs, often the fish swim upriver to spawn.
Significance of Migration in Fishes:
The significances of migration in fishes are as follows:
- For suitable feeding and spawning places
- For protection from predators
- For increasing genetic diversity
- An adaptation in character to survive extreme climatic conditions.
You can also read:
- Scoliodon – Dogfish, Classification, and Characteristics
- Characteristics and Classification of Phylum- Chordata
- Subphylum – Urochordata
- Herdmania- Sea Squirts
- Amphioxus (Lancelet)
References: Kotpal Vertebrata (Book for graduation)
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