The effects of Synthetic gonadotropin releasing hormone analogue (S-GnRHa) on artificial propagation of spotted scat, Scatophagus argus (Linnaeus, 1766)

Spotted scat Scatophagus argus is an important brackishwater species predominantly inhabited in south-west coast of Bangladesh. The aim of this study was to develop a hormonal induced reproduction protocol of farm-domesticated S. argus along with larvae rearing techniques. Synthetic gonadotropin releasing hormone analogue (S-GnRHa) was injected at the dose of 60:30 μg/kg BW (Female: Male). In female fish 20% of the total dose was applied as priming dose and 12 hours later 80% as resolving dose. The latency period ranged from 32 to 36 h was determined by observing the time between first injection and ovulation. However, after achieving full oocyte maturation and ovulation, eggs were collected by stripping and fertilization was carried out using pooled sperm from male. The mean ovulation, buoyancy, fertilization and hatching rate were found 70±1.8; 68±7.7; 40±2.3% and 53±5.2% respectively. Over the embryonic development following stages were witnessed in embryos: meroblastic cleavage (2-cell), blastula, gastrula and pharyngula. Maximum embryos hatched within 19 hr post fertilization at 28±2.0°C temperature and 28±2.0 ppt salinity. In this study, we dispense the first information on the reproduction of spotted scat in captive condition using S-GnRHa and the optimal dose limit and larval rearing techniques are established. Further studies are warranted to develop the larvae into juvenile stage under variable environmental conditions to increase the fertilization, hatching rate and survival of embryos.