Migration of fishes ppt
- 1. Zoology Department Govt. Dungar College DR. ANU KUMAR SHARMA ASSOCIATE PROFESSOR
- 3. CONTENTS Introduction. Migratory Species. Types Of Migration. Periodicity Of Migration. Methods Of Migration. Patterns Of Migration. Causes Of Migration. Factors Influencing Migration. Advantages Of Migration. References
- 4. INTRODUCTION This Migration is the seasonal movement of a large number of fish belonging to a species from one area to another in search of food or for breeding. This movement of a large number of fishes for the purpose of feeding or spawning is called Migration. According to Jones (1968), migration is “a class of movement which impels the migrants to return to the region from where they have migrated”. According to Baker (1998), it is “the act of moving from one spatial unit to another”. Migration behaviour – The phenomena in the life histories of the fish directed towards reproductive success.
- 5. MIGRATORY SPECIES Several species of fishes are migrated of mature adults for spawning and feeding. These are example of migratory fishes- 1. The cod (Gadus morhua). 2. The salmon (Salmo spp.) 3. The American eel (Anguilla rostrata). 4. The Hilsa (Hilsa ilisha). 5. The Flat fish (Pleuronectes platessa). 6. The Lamprey (Petromyzon marinus).
- 7. TYPES OF MIGRATION Migration may be of following types:- 1. Alimentary migration- This is in search of food and water. 2. Gametic migration- For reproduction. 3. Climatic migration-To search for better environmental or climatic migration. 4. Osmoregulatory migration.
- 8. PERIODICITY OF MIGRATION Migration of fishes occurs at regular intervals,which varies in different species and even within a species. Migration may be undertaken daily,monthly,seasonally,yearly or after a long gap,depending on biotic and abiotic factors. Pacific salmon may remain at sea for several year in the mud 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 (upto 20) feeding in fresh water,before undertaking spawning migration to sea.
- 9. METHODS OF MIGRATION • A fish can make migratory movements by several methods: 1. BY DRIFTING : Fishes are carried passively be water currents and do not make any effort. This is called DRIFT, and may result in “directional movements” by fish. 2. RANDOM LOCOMOTORY MOVEMENT : Locomotory movements that are random in direction lead to a uniform distribution to an aggregation.
- 10. If the fishes are released from a point in a uniform environment and spread out in all directions the process is called – DISPERSAL and leads to uniform distribution of the species. 3. ORIENTATION SWIMMING MOVEMENT : Fishes swim in a particular direction : a. Either towards or away from the source of stimulation. b. At some angle to an imaginary line running between them and the source of stimulation.
- 12. PATTERNS OF MIGRATION The form or pattern of migration differs between species, as well as in a species. Myers (1949) has used the following terms to describe fish migration: 1. DIADROMOUS FISHES a. Anadromous b. Catadromous c. Amphidromous 2. POTAMODROMOUS FISHES 3. OCEANODROMOUS FISHES
- 14. ANADRO MOUS FISHES These species have feeding areas in ocean and spend the most of their life in sea water but they migrate to fresh water rivers to spawning. Example- Salmon trout ,
- 15. CATADRO MOUS FISH A Catadromous fish lives in fresh water and enters salt water to spawn.Most of the eels are Catadromous. Examples-American eel, European eel,etc.
- 16. AMPHIDRO MOUS FISH Amphidromous fish move between fresh to salt water or vice versa is not for spawning as in others.But migration occurs regularly at some definite stage of the life cycle. Examples- Bigmouth sleeper, Mountain mullet,Torrent fish.
- 17. CAUSES OF MIGRATION Fish appear to migrate: 1. To avoid unfavourable conditions. 2. To enhance the chances of survival of the offsprings. 3. To exploit the available food in feeding areas. 4. Population pressure is also considered a possible cause of migration . The fish migrate in search of new suitable areas where food is abundant and competition is minimum.
- 18. FACTORS INFLUENCING MIGRATION Migration are influenced by various factors which may be physical, chemical and biological factors. Physical factors- i. Bottom materials ii. Depth of water iii. Temperature iv. Light intensity v. Photoperiod vi. Current turbidity
- 19. Chemical factors- i. Salinity ii. pH iii. Smell and taste of water Biological factors- i. Migration are sexual maturity ii. Food iii. Blood pressure iv. Memory v. Physiological clock
- 20. ADVANTAGES OF MIGRATION Migration is an adaptation towards abundance. It would be an advantage to have separate spawning, nursery and feeding grounds. A species whose adults return to spawn in an area where the environmental condition were similar to those under which they themselves survived when young. Thus a better egg and larvae survival would lead to a greater number of spawners on a particular ground.
- 21. REFERENCES A Textbook of FISH BIOLOGY AND FISHERIES by S.S Khanna and H.R Singh. FISH AND FISHERIES by Pandey and Shukla. Online resources.