EFFECT OF STOCKING DENSITY ON GROWTH AND SURVIVAL OF GREY MULLET Mugil cephalus IN FLOATING NET CAGES

The popular name 'mullets' generally refers to the species of the family Mugilidae, The main species of aquacultural interest are euryhaline and can be reared both in brackish- and salt-water environments. They can easily be acclimatized for culture in fresh water. In cage culture finding out the optimal stocking rate becomes an important part because stocking density directly influences the growth rate of the cultured species. Stocking density is one of the most important variables in aquaculture because it directly influences survival, growth, behavior, health, water quality, feeding and production. Optimum stocking densities need to be determined for each species and production phase to enable efficient management and to maximize production and profitability. The present study were conducted at the closed bay near Suryalanka, Bapatla, Guntur district Andhra Pradesh.

The study was on the effect of stocking density on growth and survival of grey mullet, (Mugil cephalus) in floating net cages in closed bay, Triplicate groups of mullets with an average initial weight of 0.95 g were randomly stocked in floating net cages (1m×1m×2m) at 20, 40, 60 and 80 fish/m³ designed as D20, D40, D60 and D80 respectively. Mullets in the cages were fed with 25% CP formulated diet at 10% of body weight twice daily. Sampling was done weekly. At the end of the experiment, growth in terms of body weight of fish was high in D20 than those in D40, D60 or D80, and in terms of weight gain, and specific growth rate of fish was high in D40 than those in D20, D60 and D80. There was a significant difference in the survival rates of mullets at different stocking densities. At the end of the experiment survival rates was high in D20, than those in D40, D60 and D80. Total Feed Conversion Ratio was lower in D20 and D40, followed by D60 and D80. The cages stocked with 20 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 20 fish/m³ could be recommended for producing better quality mullet fingerlings and 80 fish/m³ for highest number of seed production.