Grouper (Epinephelus malabaricus Block & Schneider) Rearing in Net Cages at Different Water Depth

Abstract

The grouper rearing in the surface floating net cage and the submerged net cage at the depth of 1.5 m from the water surface were conducted at Sriracha bay from August to December. The net cage size was 2x2x1.5 m, with 22 fish/m² and feeded with trash fish once a day. The initial sizes of fish had the average weight and average length of 262.3 g and 25.33 cm for the large ones, 154.5 g and 20.94 cm for the medium ones and 33.0 g and 12.44 cm for the small ones. The results indicated that the specific growth rate, the average weight gain per fish, the weight gain per cage, the fish production, the survival rate and the food conversion rate were not significantly different for the grouper rearing in the net cages at different water depth. The specific growth rate, the average weight gain per fish and the fish production among the various initial sizes were significantly differents. The initial small fish showed the highest specific growth rate 57.54% per month differed from the medium and large fish which gained 30.76 and 25.32% per month. The initial small fish also ahowed the highest percentage of average weight gain per fish of 906.07% which significantly different from the medium and large ones of 244.4 and 174.02%. The initial large fish gave the highest production of 55.82 kg/cage which significantly different from the medium and small ones of 37.61 and 26.67 kg/cage. The last two sizes mentioned on the last three parameters were not significantly different.