author(s)
G Suresh, K Jyotsna Rajeswari, B Chamundeswari Devi, M Raveendra, P Srikanth, D Venkatesh, V Reddy Naik, Suresh Kummari and M Chanti Babu

abstract
The present experiment was conducted to study the optimum crude protein level for milkfish, Chanos chanos seed reared in floating net cages in closed bay, Bapatla, Andhra Pardesh, India, during May to July, 2016 for a duration of 63 days. Milkfish fry were obtained through natural seed collection. Rectangular floating net cages made of bamboo poles was provided inside with 1×1×2m hapas. Milk fish with mean body weight of 2.81±0.07 g were stocked at the rate of 40 fish/m³ in each hapa in the rectangular cages. Triplicates were maintained for each treatment. Fish fry were fed with 5 artificial dry diets containing 12.5% (Control - C), 15% (T1), 25% (T2), 35% (T3) or 45% (T4) crude protein. The diets were fed at the rate of 10% of the biomass for a period of 63 days (9 weeks). Water quality parameters like D.O, p^H, salinity, NH³, NO^-2, NO^-3 and temperature were estimated at weekly intervals and were within the optimum range for culture of milk fish. At the end of 63 days growth experiment, fishes fed on 35% (T3) crude protein feed exhibited highest growth, survival, SGR, ADWG, biomass and best FCR. The subsequent positions were occupied by Treatments T4 (45%), T2 (25%), T1 (15%) and C (control). The present study showed that milkfish seed reared in floating net cages in the closed bay performed best at 35% crude protein. Based on the biological data, it was estimated that the optimal level of protein for Milkfish Chanos chanos fingerlings reared in net floating net cages was 35%.