larval dynamics fish life cycle and their feeding habit

1. Egg and Larval Dynamic
Submitted by:
Bijay Kumar Gupta
Reg. no. 2102202003

2. Topics To Be Cover
 Introduction
 Reproductive Cycle In Fish
 Spawning And Environmental Cues
 Recruitment Assessment
 Natural Food Of Commercially Important Finfish and Shellfish From Egg To
Adult.

3. INTRODUCTION
During the past few years the natural population of the freshwater fishes has been rapidly declining due to
various man-made and natural causes. According to IUCN (2000), among 266 species, 14 are going to be
extinct, condition of 12 has been severely deteriorated and 28 of them are critically endangered.
There is no sufficient information on the early development of the freshwater fishes. So, it is necessary to
undertake proper study to characterize its various stages of embryonic and larval development to
understand the biological clock and cultural techniques of these species (Rahman et al, 2009). Embryonic
studies support phylogenetic development by presenting supportive proofs to determine an organism's
ancestral forms. In addition, this period of fish life is also used in various experimental studies; especially
in aquaculture as well as toxicological studies

4. Continued…
Life starts with the unification of male and female gametes. As soon as the egg is fertilized by a sperm,
the zygote is formed and embryonic development starts and ends up at hatching.
The hatchlings further undergo organogenesis and appear as like as their parents, thus end the larval
stages.
The life stages of fish is formed of 5 stages (Demir, 2006)
1. Embryonic Phase
2. Larval Phase
3. Fry Phase
4. Ripe Phase
5. Senescent Phase

5. 1. Embryonic Phase: It is the stage which start from insemination of egg to the end of vitellus’ absorption.
The period between fertilization of egg and outlet of organism is called incubation period. This is called
aclation. Incubation ends with hatching. Embryo always comes out with head and front part of the body.
Tail comes out at last and pushes to make embryo come out easier (Langeland and Kimmel., 1997).
It is divided into two:
a. Embryo stage in egg
b. Embryo stage outside the egg
The general characteristic of embryonic stage is being fed by vitellus which is an alternate nutrient. The
embryonic stage, may refer to different stages in eggs.
Life Stages Of Fish

6. Different Embryonic Development Stages
Fertilized egg, cleavage, morula, blastula, gastrula, embryonic body formation, optic vesicle and auditory
vesicle formation, blastopore closing, tail formation and hatching stages.
In the period of larval development after hatching, until the end of the yolk sac absorption period (pre-
larvae) and subsequently until the end of metamorphosis (post larval)
 Fertilized eggs and perivitelline space
formation after the fertilization.
(Barbus grypus H, 1843)
 Germinal disc formation (x10).
(Barbus grypus H, 1843)
 Morula phase and blastomere
formation (x10).
(Barbus grypus H, 1843)
 Gastrula phase (x10).
(Barbus grypus H, 1843)

7. Continued…
 Embryonic body formation
(x10).
(Barbus grypus H, 1843)
 Head formation (x10).
(Barbus grypus H, 1843)
 Eyes and otic vesicle formation.
(Barbus grypus H, 1843)  First heart beat and movement
(x10). (Barbus grypus H, 1843)

8. Continued…
2. Larval Phase: During the larval stage which follows embryonic stage, nutrition occurs outside. After
coming out from the egg, especially teleosts gothrough some stages.
 Pre-larval stage
 Post-larval stage
2.1Pre-larval Phase:
 It is the period which starts from coming out from egg to the end of absorption of yolk sac. The most
important characteristic of prelarval stage is the existence of yolk sac.
 At the beginning of tje pre-larval phase mouth, anus and digestive tube is like straight pipe.
 Head is smaller then body, eyes are big and nonpigmented
 In some species after completin prelarval phase and taking the characteristic shape of adult called alevin
in Salmonidae fishes.

9. Different Pre-larval Stages
 A newly hatched larva.
(M. mastacembelus
B&S, 1794)
 Air bladder formation (x10).
(Barbus grypus H, 1843)
 Mouth openning,formation
(x10). (Barbus grypus H,
1843)
 Anus and tail formation (x10).
(Barbus grypus H, 1843)

10. Continued…
2.2 Post-larval Phase:
 It is the time starts after absorption finished to the end of metamorphosis.
 The length of the time changes species to species.
 It varies to species according to shape, size, body ratio, fin size, pigmentation in different sizes and order,
shape and time of organ formation in postlarval phase.
 Some organs form in postlarval phase in order to make easier to stay pelagic.
 Nutrition takes place entirely from outside in postlarval phase. Nutritions are fitoplancton, zooplancton or
mixture of both.

11. Different Post-larval Stages
 Blood vessel, digestion
channels, anus. (M.
mastacembelus B&S, 1794
 Mouth openning.
(M. mastacembelus
B&S, 1794)
 Pigmentation. (M.
mastacembelus
B&S, 1794)
 Development of
visceral organs.
(M. mastacembelus
B&S, 1794)

12. Continued….
3. Fry Phase:
 At the end of post larval phase youth phase starts.
 Except mugillidae family at other teleosts formation of scales determine the result of post-larval
phase. Formation of scales shows the first phase of youth phase.
 Scales start to develop early. The other event is developing of lateral line.
 Circulation system is formed in many species.
 Organism is a litlle copy of the mature in youth stage.
 In gonads secondary characters does not exist yet if there are.
 Like in salmonidae some species do not show remarkable metamorphosis during postlarval phase
and the individuals belong to this family pass to youth phase directly.

13. Continued…
4. Ripe Phase:
 Fish gonads are fully developed and have capability to reproduce capability at intervals.
 Secondary characters are developed in some fish species (if any).
5. Senescent Phase:
 Firstly sexual activities decreases then completely disappears.
 Similarly the growth of height slows down or stops.

14. Reproductive Cycle Of Fish
 A majority of teleost fishes are seasonal breeders, while a few breeds continuously.
 Among the seasonal breeders, there is wide variation in the time of the year when
breeding occurs.
 Fresh water temperate zone fishes spawn in spring and early summer, while others
such as the salmonids do so in autumn.
 A few fishes breed only once in their long-life spawn e.g., salmon. The fresh water
eel breeds only once in 10-14 years.
 In the Indian subcontinent, a vast majority of the fresh water fishes breed during the
monsoon season when rainfall is heaviest (Jhingran, 1975).

15. Continued…
Seasonal breeders exhibit rhythmic changes in the structure and physiology of ovary and testes in
different seasons. These changes are demarcated into five phases –
1. Resting phase (December - January)
2. Preparatory phase (February – April)
3. Maturing phase (may – June)
4. Spawning phase (July - September)
5. Post spawning phase (October – November)

16. Light
Neurohormonal
Natural food
Water quality
Temperature
Factor Affecting The Fish Reproductive Cycle
 The reproductive cycle of fish highly affected by the following factors:
 Environmental factors – light, temperature, water quality parameters etc.
 Intrinsic physiological factors – hormonal, neurohormonal.
 Nutritional requirements of fish – natural food, feeding pattern, balanced diet
required for optimum gonadal growth.

17. Ovarian Cycle
In the female fishes development of ovary taking place, it is also called ovarian cycle. In this cycle
several phases take place as given below.
1. Resting phase
 Oocytes in the stage I and II.
 Normally it commences between August to September.
 The ovary looks small, thin, thread like, translucent, pale or dirty white in colour with
inconspicuous vascularization

18. Continued…
2.Preparatory phase-
 Oocytes in the stage III and IV.
 During October to December the ovaries become slightly larger , thicker, opaque and yellowish in colour.
 There is an increase in the weight of ovary.
3.Maturing phase or prespawning phase-
 Oocytes in the stage V and VI.
 Generally, it commences between January to march. There is
a gradual increase in the volume and weight of the ovaries
and occupy about 2/3 to ¾ th of body cavity.

19. Continued…
4.Spawning phase-
 Oocytes in the stage VII.
 Spawning phase usually commences between April to June.
 During this phase, the ovaries show a well-marked increases in their volume and weight.
 They are turgid and yellow in colour with a large number of translucent eggs.
 Ova may be extruded by applying a gentle pressure on the abdomen
5.Post spawning phase-
 Oocytes in the stage I and II
 It is also called as spent phase. Normally it runs between July and early August.
 The ovaries are flaccid, shrunk and sac-like, reduce in volume with dull colour.

20. Oogenesis
 Oogenesis is a highly orchestrated process that depends on regulation by autocrine/paracrine
hormones and growth factors.
 In oogenesis first of all oogonia grows from germ cell,
 Then these oogonia gives primary oocytes by means of mitotic division which further undergoes
meiosis I to produce secondary oocyte with small size polar body.
 The secondary oocyte undergo arrest phase at anaphase I.
 Which will further complete meiosis II when come into the contact with sperm to produce ripen ova
along with secondary polar body.

21. Oogenesis
Oogenetic division
Oocyte Maturation

22. Gonadosomatic Index
Gonadosomatic index of the species has also been widely used to indicate the maturity and periodicity
of spawning and predicting the breeding season of the fish, and can be calculated by the following
formula -
GSI =
Gonadosomatic index (GSI) of the fish
increases with the maturation of the fish,
being maximum during the peak period of
maturity and declining abruptly after
spawning. The GSI of river catfish
(Glyptothorax pectinopterus) was found to
be highest in June and least in November
(Khanna and Pant, 1967)
GSI =
Weight of gonad
Weight of body
x100

23. Testicular Cycle
Parallel to the ovarian cyclic change taking place in female, the primary reproductive organ of male i.e.
testes also undergoes rhythmic changes which are summarised below –
1. Resting phase
2. Preparatory phase
3. Mature phase
4. Spermiation phase
5. Post spermiation phase

24. Spermatogenesis
Spermatogenesis is a highly organized and coordinated process, in which diploid spermatogonia
proliferate and differentiate to form mature spermatozoa. Spermatogenesis process morpho-functionally
can be divided in three different phases:
 The mitotic or spermatogonial phase with the different generations of spermatogonia (i.e.,
undifferentiated spermatogonia including the stem cells, and differentiated or differentiating
spermatogonia);
 The meiotic phase with the primary and secondary spermatocytes;
 Spermiogenic phase with the haploid spermatids emerging from meiosis and differentiating –
without further proliferation – into motile, flagellated genome vectors, the spermatozoa.

25. Spermatogenesis
Spermatogenesis is
the process by
which haploid
spermatozoa
develop from germ
cells in the
seminiferous
tubules of the testis.

26. Spawning and environmental cues
After the complete maturation of oocytes the final expulsion of egg outside the body into surrounding
occurs, which is termed as spawning followed by fertilization. Each species spawn during specified
period under favourable condition. The part of the year during which species attain their full maturity
and spawning occur in population are called as the breeding season of that species.
 March to early June in freshwater catfish (Mystus seenghala) (Sathyanesan, 1962),
 From April to September in Tor tor (Rai, 1957),
 From June to September in Clarias batrachus (Lehri, 1968),
 From July to September in Channa punctatus (Belsare, 1962),
 From June to August Channa gachua (Khanna and Sanwal, 1971),
 From April to August in Rasbora daniconius (Raizada, 1971), and
 From October to December in Suchizotharax richardsonii (Bisht, 1972).
Spawning period of different species

27. Environmental cues on spawning
As we all know that, environmental factors plays very crucial role in fish reproduction as the
environmental factors stimulate the release of different hormones which trigger the reproductive cycle.
The temperature and photoperiod is the main environmental factor that act on receptor of CNS and release
Dopamine, GABA, Serotonin which stimulate hypothalamus which secrete GnRH (gonadotropin releasing
hormone) which further act on pituitary gland to release GTH I (equivalent to FSH) and GTH II
(equivalent to LH).GTH I act on oocyte envelop due to this steroidogenesis starts and form estrogen,
progesterone and androgen these hormone through circulation act on liver to secrete vitellogenin which
further act on ooplasm and vitellogenesis occur. Whereas GTH II act on oocyte envelop for complete
maturation and ovulation. Finally, the gravid oocyte will expulse out of body and fertilize with male
gamete

28. Flow Chart Of Environmental Cues
Environmental cues (Temperature & Photoperiod)
Photoreceptor (Eye, Pineal)
Brain
Melatonin
Neurohormone
GnRH
GABA
Serotonin
Hypothalamus
Pituitary
GnRH
GTH I, GTH II
Ovary
Steroidogenesis
Estrogen, Progesteron, Androgen
Liver
Gametogenesis
Vitellogenin

29. Recruitment Assessment
 Recruitment is the process in which young fish enter the exploited area and become liable to contact
with the fishing gear.
 This may involve an actual movement, as in the North Sea plaice, which moves, when relatively old
(about three to four years), from the shallow nursery area along the coast into the main fishing
grounds.
 Recruitment may involve only a change in habit, such as in the North Sea haddock, where young and
old occur in the same areas, with the very young fish being pelagic, and recruiting to the exploited
phase when they take up a demersal habitat in the autumn of their first year of life.
 Mathematically, the important quantity is tr = mean age at recruitment.

30. Important Terms for Recruitment
 Recruitment process: The act of small fish transitioning to a larger size and greater age at which they
will no longer experience density-dependent mortality.
 Recruitment period: Refers to the time during which fish are going through the recruitment process, and in
which we expect mortality to be density-dependent.
 Recruited fish or “recruits”: Fish that have just transitioned out of the recruitment period and now
experience only density-independent mortality.
 Density-dependent mortality: The natural mortality of fish (and thus their survival) depends on the
numbers of fish in an area (which is the density); the type of mortality that occurs during the
recruitment process.
 Density-independent mortality: When the natural mortality (and survival) of fish does not depend on
the numbers of fish in an area (density); typically occurs for very small fish (and eggs) that have not
yet begun the recruitment period as well as for larger fish that have survived the recruitment period.
 Settlement: Refers to larval fish beginning to associate with structural or physical habitat (i.e.,
“settling” out of the water column) and is usually associated with the beginning of the recruitment

31. Continued…
Diagram showing how the type
of mortality (top shaded box)
corresponds to fishes’ life stage
(bottom shaded box). Please note
the number of fish here does not
represent the survival, and the
two “groups” of larger fish in the
density-independent mortality
section represent two age-classes.
Credits: Kai Lorenzen, UF/IFAS

32. Method Of Recruitment Assessment
CASAL (C++ Algorithmic Stock Assessment Laboratory) is an advanced software package developed
by NIWA for fish stock assessment. The software implements a generalised age- or length-structured fish
stock assessment model that allows a great deal of choice in specifying the population dynamics,
parameter estimation, and model outputs.
MULTIFAN-CL is a computer program that implements a statistical, length-based, age-structured model
for use in fisheries stock assessment

33. Natural Food For Fish
Food of Carp Fry
 Newly hatched larvae of about 5 mm have a yolk sac, on which they subsist for at least two days. Then
they start feeding on organisms found in water.
 Three to four days old carp fry measuring about 7 mm feed primarily on zooplankton.
 Food habits of all the species of major carps are identical at the fry stage. They all start feeding on
cladocerans and the animalcules.
 Cladocerans and rotifiers form the bulk of the food consumed by these young fish. Cladocerans are the
most preferred food of carp fry.
 A single fry may consume as many as 150 cladocerans within 24 hours.
 Species of Daphnia, Moina. Cyclops, Diaptomus, Brachionus, Keretella forms the most important
components of zooplankton food.
 Carp fry raised on phytoplankton alone is very weak and the survival is very poor so far as carps are
concerned.
 Phytoplankton organisms have a resistant cell wall, which is indigestible by tender fry. Zooplankton
especially cladocerans are consumed eagerly and also digested quickly.

34. Continued…
Food of Carp Fingerlings
 Each species of major carps at this stage have a choice for its own preferential food.
 However, there is only little change in food habits of catla fingerlings which continue to feed largely
as before on cladocerans and other animalcules, making very little, use of microscopic plants floating
in water.
 Rohu fingerlings start feeding on microscopic plants, vegetable debris, deritus and mud in addition to
few cladocerans.
 The food of mrigal fingerlings is more or less same as that of rohu. but they consume relatively larger
quantities of decaying vegetable debris, phytoplankton organisms, sand and mud.

35. Continued...
Food of Carp Yearling and Adults
 Catla do not exhibit any marked change in food and feeding habits even at the yearling
and adult stage. At all stages of their growth, their preferred food is largely composed of
cladocerans, copepods and rotifiers, although they do swallow algae, vegetable debris and
other organisms floating in the water.
 Rohu at this stage consumes, considerable quantity of bottom sand, mud, vegetable debris
and planktonic algae. But, have very little proportion of cladocerans and other
animalcules in their diet.
 Mrigal at fingerling and adult stages have a common diet as that of rohu of the same size
and age. But, consume more quantities of organic and vegetable debris, microscopic
plants, sand and mud. Mrigal feeds mostly on debris and decaying matter.

36. FISH FEEDING HABIT FOOD TYPE
Mystus seenghala,
Wallago attu,
Carnivorous and Predatory Fish fry, insects and its larvae,
fingerlings, small fishes, tadpoles,
frogs, etc
Channa marulius,
Channa striatus, Chitala
chitala
Carnivorous and Predatory Fish fry, insects and its larvae,
fingerlings, small fishes, tadpoles,
frogs, etc.
Clarias batrachus Omnivorous Insects, worms, crustaceans, fish fry,
insects larvae, decaying organic maters,
etc.
Heteropneustes fossilis Herbivorous
Algae, microscopic plants, vegetable
matters, detritus, sand and mud, etc.
Osphronemus goramy Herbivorous They mainly feed on aquatic plants and
algae.
Oreochromis
mossambicus
Herbivorous They mainly feed on aquatic plants and
filamentous algae.
Ctenopharyngodon idella
Herbivorous They voraciously feed on aquatic
vegetation.
List Of Natural Food
For Fish

37. fish Feeding habit Food type
Hypopthalmicthys molitrix
Plankton feeder
Unicellular algae, rotifers,
decaying microorganisms,
detritus, etc.
Catla catla Plankton feeder
Microscopic plants, Algae,
rotifers, insects, crustaceans, etc.
Cirrhinus cirrhosus Omnivorous
Algae, decaying plants, and
animal matters, detritus and
mud, etc.
Tor putitora Omnivorous
Algae, decaying organic matter,
insects, rotivers, protozoans, etc.
Tor tor Omnivorous
Macro vegetation, filamentous
algae, mollusks, sands and muds,
etc.
Cyprinus carpio Omnivorous Algae, macro-vegetation,
insects, rotifers, crustaceans,
etc.
List of natural food
of fish

38. References
a. Aral, Faruk & S?ah?no?z, Erdinc & Dog?u, Zaf Embryonic and Larval Development of Freshwater Fish. 10.5772/17687.
b. 2. REPRODUCTIVE CYCLES AND ENVIRONMENTAL CUES. Fao.
https://www.fao.org/3/X5742E/x5742e03.htm?msclkid=8c4041b9bccc11ec9ff6bfcc25ce05d9
c. Fish in Aquaponics - RGJ Aquaponics. Rgjaquaponics. https://rgjaquaponics.weebly.com/fish.html
d. (PDF) Fish Reproduction. Researchgate.
https://www.researchgate.net/publication/312162015_Fish_Reproduction?msclkid=97a9937cbcee11ecb4d2ce95b3fc1d8a
e. reproductivebiology-in-carp.pdf. Courseware. http://courseware.cutm.ac.in/wp-content/uploads/2020/06/reproductivebiology-in-
carp.pdf?msclkid=3e8f3949bcf611ecae1b076652ec11dc
f. (PDF) Next generation mothers: Maternal control of germline development in zebrafish. Researchgate.
https://www.researchgate.net/publication/268578716_Next_generation_mothers_Maternal_control_of_germline_development_in_ze
brafish
g. Liu, X., Huang, Y., Tan, F., Wang, H., Chen, J., Zhang, X., Zhao, X., Liu, K., Wang, Q. & Liu, S. (2022, March 1). Single-Cell Atlas
of the Chinese Tongue Sole (Cynoglossus semilaevis) Ovary Reveals Transcriptional Programs of Oogenesis in Fish. Frontiersin.
https://www.frontiersin.org/articles/10.3389/fcell.2022.828124/full#:~:text=Oogenesis%20is%20a%20highly%20orchestrated%20pr
ocess%20that%20depends,molecular%20mechanisms%20that%20regulate%20fish%20oogenesis%20remain%20elusive.?msclkid=
28cb8643bd6e11eca31e07abeaa42d99
h. CAPAM_Selectivity Workshop_Series Report_August 2013.pdf. Capamresearch.
http://www.capamresearch.org/sites/default/files/capamresearch.org/sites/workshops/selectivity/CAPAM_Selectivity%20Workshop_
Series%20Report_August%202013.pdf?msclkid=f6c8b4a1be1e11ecb1afd53ea5179b04
i. Maturation and spawning in fish | The Fish Site. Thefishsite. https://thefishsite.com/articles/maturation-and-spawning-in-
fish?msclkid=68ee1f0abd7d11ecba1e730bf45485e4
j. pdfFAFA22200.pdf. Edis. https://edis.ifas.ufl.edu/pdf%5CFA%5CFA22200.pdf

39. Thank You