Скачать или смотреть Handbook of Fisheries and Aquaculture|Migration in Fishes|Types of Migration In Pisces

Handbook of Fisheries and Aquaculture|Migration in Fishes|Types of Migration In Pisces #jrf2024

Migration In Fishes/Pisces || Types Of Migration|| By Dr. Suneet Godara
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MIGRATION OF FISHES


2. INTRODUCTION- : Few species travel long distance moving from place to place in search or food or for breeding . This movement of a large number of fishes for the purpose of feeding or spawning is known as Migration. According to baker (1998) it is ‘ the act of moving from one spatial unit to another’. According to nikolsky ( 1963) – ‘ migration is an adaptation toward increasing the abundance of a species .’ Migration behaviour is of course one of the phenomena in the life histories of the fish directed toward reproductive success.

3. MIGRATORY SPECIES- Several species are migrated of mature adults for spawning and feeding. These are example of migratory fishes- 1. The cod ( Gadus morhua) 2. Herring (Clupea harengus) 3. Salmon (salmo sp.) 4. Eel ( Anguilla anguilla, A. Rostrata and A. japanica 5. Hilsa ( Hilsa ilisa) 6. Three- spined stickle back ( Gasterosteus aculeatus) 7. The lampreys ( Petromyzon marinus) 8. The tunnas ( Thunnus thynnus)

4. TYPES OF MIGRATION- Migration may be the following types: a. ALIMENTORY MIGRATION – This is in search of food and water. B. GAMETIC MIGRATION - For reproduction . C. CLIMATIC MIGRATION - to secure more suitable climatic conditions. d. OSMOREGULATORY MIGRATION.

5. METHOD OF MIGRATION- A Fish can make migratory movements by several methods: 1. BY DRIFTING : Fishes are carried passively be water currents. This is called DRIFT, and may result in ‘directional movements’. If the over all water movement is in one direction. 2. RANDOM LOCOMOTORY MOVEMENT- Locomotary movements that are random in direction lead to a uniform distribution or to an aggregation. If the fishes are released from a point in a uniform enviorment and spread out in all directions the process is called – DISPERSAL and leads to uniform distribution of the species.

6. 3. ORIENTATION SWIMMING MOVEMENT- Fishes swim in a particular direction: a. Either towards or away from the source of stimulation a. At some angle to an imaginary line running between them and the source of stimulation.

8. PERIODICITY OF MIGRATION-  most of migration occurs at regular intervals and may be daily, monthly , seasonally , yearly biannually or longer. Thus , pacific salmon may remain at sea for several years before returning to the spawning grounds. Larvae of Petromyzon marinus may spend several year in the mud before metamorphosis and migrating to sea. Eel spend several years (up to 20 ) feeding in fresh water , before undertaking spawning migration to sea. The periodicity thus varies between different species , and even within a species and appears to be due to many biotic and abiotic initiating factor.

9. MARKING AND TAGGING -: Information about the pattern of fish migration , its direction and speed of movement , can be studied by marking and tagging of fish followed by rapured. The mark or tag must be easily identible and must stay with the till end of the study . Many types of tags have been developed for attachment to the fish for recognise.

10. PATTERNS OF MIGRATION-: The form or pattern of migration differs between species ,as well as within a species , myers (1949) has used the following terms to describe fish migration : 1. DIADROMOUS FISHES A. Anadromous (salmon and hilsa) B. Catadromous ( anguilla) C. Amphidromous 2. POTAMODROMOUS FISHES 3. OCEANODROMOUS FISHES

1- DIADROMOUS FISHES-:  these are truly migratory fishes which migrate between the sea and fresh water and are three types:

 A. ANADROMOUS FISHES -: diadromous fishes which spend a major part of there lifes in the sea but migrate to fresh water during breeding period for spawning. Thus , many marine fishes like the Salmon shad Lampray and Hilsa ,travel long distances in te sea and run up the river to spawn in fresh water . Salmon and Hilsa have been found to travel several thousand km in the sea, then several hundred km inland to reach the spawning ground , after egg laying , the spend fishes return to feeding places in the sea.

 2. CATADROMOUS: This group including diadromous fishes which spend a major of their lives in fresh water but migrate to the sea for breeding purpose. Thus the fresh, water eel Anguilla travels several thousand km starting from the rivers and reaching the spawning grounds in the sea. After egg laying.

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