Migration in fishes

BY

prachee rajput 2nd SEM Zoology

Dept. Of Zoology and Applied Aquaculture Barkatullah University Bhopal

SYNOPSIS

IntroductionTypesa) Diadromousb) Anadromousc) Catadromousd) Oceanodromouse) Potadromous Causes of migration References

Introduction• It is sometimes the case in fishes that the life history

needs a population ( e.g, foraging and reproduction) cannot be met by a single habitat . This is due to variability in the habitat conditions (e.g, temperature), or to the changing needs of the population itself (e.g, foraging habitat vs. Spawning habitat). In such cases the fitness of individuals benefits from movement to an alternate habitat. As a result, many fishes have evolved a life history that includes coordinated movement from one habitat to another . This synchronous, directed movement of part or all of a population between discrete habitats is called “migration” .

TYPES

Fish migration are typically grouped into five categories, based somewhat arbitrarily on their relationship to the seawater/freshwater boundary.

a) Diadromousb) Anadromousc) Catadromousd) Oceanodromouse) Potadromous

Diadromous:

It is derived from the classical Greek word where “dia” means “through” and “dromous” means “running”. In this type the fishes migrate between fresh water and sea water e.g, pacific salmonids

Anadromous:

It is derived from a Greek word where “ana” means “up” and “dromos”means “course” . In this fishes migrate from the sea up into fresh water to spawn, or stay entirely in sea water and migrate upstream to spawn e.g, pacific salmon species such as Chinook (king), Coho (silver) etc.

Catadromous:

It is derived from a Greek word where “kata” means “down” and “dromos” means “course”. In this type the fishes migrate from fresh water into the sea to spawn, or stay entirely in fresh water and migrate downstream to spawn e.g, eels of genus Anguilla.

Oceanodromous:

In this type fishes live and migrate only in sea water e.g, Atlantic herring, sardines etc. These fishes nearly migrate to colder water regions for the purpose of spawning and then return to their parental area.

Potadromous:

Migrations that occur entirely within freshwater are classified as Potadromous. Potadromous migrations can occur solely in lakes e.g, lake trout, salvelinus namacycusb.

Causes of migration

According to some scientists the migration in fresh water fish arise basically as a result of insufficient food supply in rivers, whereas in marine fishes, it is more favourable condition and better protection for developing eggs in the rivers than in open sea. there are three mechanisms on which migration can brought among these fishes.

a) Gametic migrationb) Alimental or Feeding migrationc) Climatic or wintering migrationd) Osmoregulatory or protective migration

Gametic migration: This type of fish migration is brought for better survival and proper development of their eggs and larvae.

Alimental or Feeding migration: This is one of the important migration which is brought about mainly due to shortage of suitable food supply in the wintering or spawning ground.

Climatic or wintering migration: Such type of migration can help to survive in a protective area which depend on environmental changes.

Osmoregulatory or protective migration: Spawning, feeding and wintering migration can all be regarded as the protective migration as they ensure the further life of fish.

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