Physiology and reproduction in fish

All living species of fishes existing in the world at present, a wide variety of patterns of reproduction present as follow, uni-sexuality, bisexuality, hermaphroditism and parthenogenesis. Like other vertebrates, the fishes usually reproduce sexually and in a quite large number of them, spermatozoa and eggs are formed in separate individuals and the gametes are expelled in the water where fertilisation occur. To increase and standardise an efficient hatchery system for producing the young fish of good quality insufficient numbers of a given species, it is essential to know the details of its natural breeding. It involves the study of sexuality of a given fish, sexual dimorphism, reproductive cycle, time, season and place of reproduction. Also, fecundity, spawning pattern, parental care and larval life history. Reproductive physiology of fish (RPF) is a vast scientific field, which directly concerns a set of physiological processes essential for reproduction, beginning with egg fertilisation and ending with sexual behaviour and spawning. Processes include gonad differentiation, puberty, male and female gametogenesi, timing of reproductive cycles.