Physiology of Finfish and Shellfish (2+1)

3.1.17. Maturation and spawning

Testes and ovaries become mature after undergoing through well marked histo-morphological alterations and increase in size. This is called maturation and the final expulsion of sperms or ova from the body into the surrounding water is called “spawning” followed by fertilization. Each species spawns during a specified period under favourable conditions. The part of the year during which the gonads attain full maturity and spawning occurs in the population is called breeding season of the species. After spawning the residual germ cells undergo a brief rest and enter the maturation cycle again to produce gametes for the next season.

Teleosts vary in the rhythm of maturation of oocytes. Some species spawn only once, others twice, while still others may spawn several times during a year.

According to Qasim (1973), many Indian marine fishes appear to be continuous breeders and have a long spawning period extending upto 7-9 months. Maturation and spawning period varies in different species and even in the same species collected from different places. Temperature, Salinity and photo period and duration are considered important factors controlling maturation of gonads. Most of the Indian freshwater teleosts spawn after the onset of monsoon. The asian seabass lates callcarifer spawns during june to october, while the grey mullet mugil sephalus spawns during mansoon seasons from october to june.