Environmental factors such as photoperiod, temperature, and rainfall influence fish reproduction. Photoperiod regulates the reproductive cycle through melatonin production, with longer photoperiods stimulating gonadal development. Temperature also controls melatonin and directly impacts gametogenesis, hormone production and secretion. Certain species spawn in response to rainfall and changes in water parameters. Careful control of these environmental factors is necessary to induce spawning.

1. 

2. 
 Introduction
 Environmental factors
 Photoperiod
 Temperature
 Rainfall
 The polyhouse techniques
 Conclusion.
OUT LINES

3.  The environment is the surrounding or conditions in
which a parson, animal or a plant lives or operate.
INTRODUCTION

4. 
 The environmental factor or ecological factor or eco-
factor is any factor that influences living organisms.
Divided into 2 parts:
Abiotic factor: temperature, photoperiod,
pH, rainfall, salinity etc.
Biotic factor: predator, parasitism etc.
ENVIRONMENTAL FACTOR

5. 
Photoperiod
Pineal organ in melatonin rhythm
Photoperiodic signals transduces by melatonin
Hypothalamic (preoptic anterior) pituitary gonadal axis
Control reproductive timing by neuroendocrine signals
PHOTOPERIOD

6. 
Regulate the production of sexual steroid and growth
factor in the gonad
 In spring and early summer spawners the gonadal
recrudescence is often stimulated by long
photoperiod with warm water temperature (Htun-
Hun 1977).
 Increasing photoperiod leads fast gonadal
development.
 Greater stimulation of vitellogenesis increased with
photoperiod (Scott 1979).
 Maximum response in terms of percentage of fish
attaining sexual maturity occurred when there are 14
to 16 hours of light cycle.

7. 
 Increasing day length/photoperiod may be the most
important cue for triggering the start of yolk
production and incorporation into the developing
gonad.

8.  Water temperature is probably the major
environmental cue for the bath initiation and
termination of the spawning season.
 Control the melatonin production.
 Melatonin is the first signal of fish reproduction.
TEMPERATURE

9. 
 Temperature have direct action on
 Gametogenesis (Lofts et. al., 1968)
 Pituitary gonadotropin secretion (Brelon
and Billard 1977)
 Metabolic clearance of hormone (Peter
1981)
 Responsiveness of liver to estrogen in the
production of vitellogenesis (Yaron et. al.,
1980)
 Responsiveness of gonad to hormonal
stimulation (Jalabert et. al., 1977)

10. 
 In O. latipes long photoperiod fail to stimulate
gonadal recrudescence at temperature below 10
degree C. (Yoshioka 1970).
 Low temperature favor the formation of primary
spermatocytes (meiotic phase), but higher
temperature promote spermatogonial proliferation
and spermiation (Ahson 1960).
 In case of marsh killifish (Fundulus confluentus) low
temperature promote the early phase of oocyte
growth ( Harrington 1959).
 In rainbow trout low temperature important to
ovulation, otherwise the ova survive only a short
time ( Billard and Breton 1977).

11. 
 In gulf croaker (B. icistia) ovulation and oocyte
hydration is influenced by water temperature above
17 degree C.
 Rise in temperature is also implicated in the
spawning.

12. 
 Stimulate the species for spawning by
 Developing petrichor (dilution of electrolytes
like chloride)
 Lowering the temperature
 Increasing oxygen content
 Changes in pH
RAINFALL

13. 
 Species that has been reported to spawn in relation
to rainfall or flood is
 C. garipinus (Bruton 1979)
 H. fossilis ( Sundararaj and Vasal 1976)
 IMC (Sinha et. al., 1974)
 Puntius spp. (Lake 1967)
 Tor unicolor (Beumen 1979)

14. 
The polyhouse techniques
 First established
in FRC, AAU
Jorhat by Dr.
Bibha Chetia
 Made up of UV
stabilized LDPE
film.

15. 

16. 
If specific environmental
requirement are not met than the fish
will not spawn and the gonadel
component become atresic
degenerates and be reabsorbed.
CONCLUSION

17. 