This document discusses the migration patterns of different fish species. It identifies four main types of migration: anadromous, catadromous, potamodromous, and oceanodromous. Anadromous fish migrate from salt water to freshwater to breed, while catadromous do the opposite. Potamodromous fish migrate within freshwater systems, and oceanodromous migrate long distances within the ocean. Examples of each type are provided, along with factors like temperature, salinity, food availability, and hormones that influence fish migration.

1. MANI BHASKAR KUMAR
1802101018
FRM- 122
2nd SEM

2. (i)To avoid unfavourable conditions: light,
temperature, pH, water currents
(ii)Breeding
(iii) To enhance the survival of offspring's
(iv) Scarcity of food in feeding areas
(v)Population pressure (competition and predation)

3. To find suitable feeding and spawning ground
To protection from predators
Survive from extreme climatic conditions
To survive and existence for increasing genetic diversity

4. MIGRATORY FISHES
Anguila anguila
Anguila vulgaris
Anguila rostrata
Salmo solar
Hilsa hilsa

5. 1. Diadromous – Travel between sea & fresh water
a) Anadromous (most of life at sea, breed in fresh
water) - from sea water to fresh water (marine fishes)
Eg. Salmons, Indian shad
b) Catadromous (most of life in fresh water, breed at
sea) - from fresh water to sea water for spawning
(fresh water fishes) Eg. Eels
2. Amphidromous – migrate between water types at
some stage other than breeding
3. Potamodromous – Migrate within a fresh water
system - long movement within fresh water. Eg. Carps,
trouts.
4. Oceanodromous (Migrate to different regions of the
ocean) – from native place to a far off place. Eg. Tunas,
mackerels

6. 1. Anadromous Migration
Fishes which migrate from the sea into fresh
water to spawn
Ones which stay entirely in sea water and
migrate upstream to spawn
Anadromous fish, born in fresh water, spends
most of its life in the sea and returns to fresh
water to spawn
Adults usually die after spawning
Their adaptations to conditions of different
habitats are particularly with regard to salinity
of the water
Common examples - Salmon, Trout, Hilsa,
striped bass, Sea lamprey and sturgeon

7. 2. Catadromous Migration
 Catadromous fishes are ones which migrate
from fresh water into the sea to spawn e.g. eels
of the genus Anguilla (19 species)
 It travels several thousand km starting from
rivers reaching spawning grounds in sea
 After spawning adults die
 Larvae of eel drift from spawning grounds, takes
several months to 3 years, to reach river &
undergo metamorphosis to become adults
 Young ones are born in the ocean, mature in
freshwater or estuarine habitats, and return to
the ocean to spawn

8. 3. Potamodromous Migration
 The movement is confine to fresh water - e.g. carps,
trouts, catfishes
 Travels long distances in rivers to locate suitable
spawning grounds (upstream or downstream)
 After laying eggs, the parents return to the feeding
area as food is available only for the young ones &
cannot support the adults
 Migration may also be - Competition due to increase
in population
 Scarcity of food may also force fishes to migrate
other places, where food is abundant

9. 4. Oceanodromous Migration
 Travel long distances with in sea to spawn & return
to the feeding areas
 There are no barriers within the sea and fishes have
learned to migrate in order to take advantage of
favourable conditions wherever they occur
 They differ mainly from one another by the extent of
their migration
 Examples- Mackerels, Tunas, Cod, Herrings
 During migration these species visit spawning areas,
nursery areas, feeding areas, winter area etc.,

10. Migration of Herring
 North Atlantic and North pacific Oceans and exhibit
seasonal or annual spawning migration to the
spawning ground near the coast
 After spawning , the larvae drift along the water
current to wintering area near the coast, where they
feed and grow
 On becoming adult, they join the older fish in
migration cycle and return to spawning area when
mature
 This takes 4-6 years

11. Factors influencing migration
 Influenced by
 Physical factors
a) Temperature
b) Light intensity
c) Photoperiod
d) Water current
e) Turbidity
f) depth
 In sea water rise in temperature provides
stimulus to Salmon for Migration.
 In fresh water temperature rise fishes moves
upstream for spawning

12. Factors influencing migration
 Chemical factors
a) pH
b) Salinity
c) Odour
d) Taste of water
 Salinity of water restricts the movement of fishes.
 Freshwater species are stenohaline (intolerant to
large salinity changes).
 Hence they remain confined to fresh water do not
undertake migration involving long distances
 But some species like Salmon, Hilsa, Anguilla are
euryhaline and can adjust to large salinity variations
i.e. Diadromous fishes

13. Factors influencing migration
 Biological factors
a) Food
b) Memory
c) Stage of sexual maturity
d) Predators and competitors
e) Hormones
 Availability of food is the primary factor for
the survival of juveniles
 Memory guides some species during
migration e.g. Salmon returns to the same
area of river for spawning, where its own
hatching & development took place

14. Role of Hormones in migration
 Observed in Diadromous fishes
 The osmo and ionic regulation in these
species is controlled by Hormones secreted
by the pituitary gland e.g. Prolactin,
Corticotrophin, growth hormone
 Prolactin is the most important hormone that
acts on gills, skin, kidney, urinary bladder
and the intestine and influence the water and
ion regulation
 It also reduces the loss of Na ions in the
fresh water fishes (Eel)