BIOLOGY

1. Zoology Department
Govt. Dungar College
DR. ANU KUMAR SHARMA
ASSOCIATE PROFESSOR

2. MIGRATION OF
FISHES

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).

6. YELLOW EYE
ROCKFISH
THE COD
FISH

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.