CHAMUNDESWARI DEVI, B (MAJOR)RAVINDRA KUMAR REDDY, DMADHAVAN, NSURESH, GALIDEVAERA2021-07-162021-07-162016-11https://krishikosh.egranth.ac.in/handle/1/5810170613THESESThe present studies were conducted at the closed bay near Suryalanka, Bapatla, Guntur district on “Studies on growth and survival in nursery rearing phase of finfish species in floating net cages for mariculture”. Total three (3) studies were conducted. The first study was on the effect of stocking density on growth and survival of milkfish, Chanos chanos in floating net cages in closed bay, Bapatla. Triplicate groups of milkfish with an average initial weight of 2.90±0.32 g were randomly stocked in floating net cages (1m×1m×2m) at 20, 40, 60 and 80 fish/m3 designated as D20, D40, D60 and D80 respectively. Milkfish in the cages were fed with 35% CP formulated diet at 10% of body weight twice daily. Sampling was done weekly. At the end of the stocking trail, growth in terms of body weight, weight gain, specific growth rate of fish were high in D40 than those in D20, D60 or D80. There was no significant difference in the survival rates of milkfish at different stocking densities. Total Feed Conversion Ratio was lower in D40 followed by D20, D60 and D80. The cages stocked with 40 fish/m3 have highest growth performance and 80 fish/m3 showed highest biomass performance. Water quality parameters were at optimum level during study period. Results suggest that 40 fish/m3 could be recommended for producing better quality milkfish fingerlings and 80 fish/m3 for highest number of seed production. Second study was conducted to study the effect of stocking density on growth and survival of seabass, Lates calcarifer in floating net cages in closed bay, Bapatla. Triplicate groups of seabass with an average initial weight of 1.29±0.12 g were randomly stocked in floating net cages (1m×1m×2m) at 20, 40, 60 and 80 fish/m3 designated as SD20, SD40, SD60 and SD80 respectively. Seabass in the cages were fed with 45% CP formulated diet at 10% of body weight twice daily. Sampling was done weekly. At the end of the stocking trail, growth in terms of body weight, weight gain, specific growth rate and survival rate of fish was high in SD20 than those in SD40, SD60 and SD80. Total Feed conversion ratio was lower in SD20 followed by SD40, SD60 and SD80. The cages stocked with 20 fish/m3 have highest growth performance and survival. 20 fish/m3 showed better survival percentage than SD40, SD60 and SD80. Water quality parameters were at optimum level during study period. Results suggest that 20 fish/m3 could be recommended for producing better quality seabass fingerlings and 80 fish/m3 for highest number of seed production. Another experiment was conducted to study the optimum crude protein for milkfish, Chanos chanos seed in floating net cages. Milkfish fry were obtained through natural seed collection. Rectangular floating net cages made of bamboo poles was provided inside with 1×1×2m hapas. Predatory net and bird net were provided. PVC drums filled with air were fixed to the net cage for floating. 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, pH, 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 and survival performance at 1% and 5% level of significance. The present study showed that milkfish seed reared in floating net cages in the closed bay performed best at 35% crude protein.EnglishThesis