1998 Volume 11 Issue 1 Pages 27-34
A stocking limitation of tilapia Oreochromis niloticus based on the balance of oxygen at 28°C in the fish-rearing closed tank which had been developed in order to establish CERAS, was estimated. Three experiments were conducted. They were measurements of the oxygen supply of the O2/CO2 exchange unit and released oxygen from the system (experiment I), measurements of the oxygen consumption and of ammonia excreted by O. niloticus under 60% standard feeding rate and photoperiod 12L12D (experiment II) and measurements of the oxygen supply and nitrifying activity of bacteria under supplementation of (NH4) 2SO4 (experiment III). The oxygen supply of the O2/CO2 exchange unit can be described by the equation, OS=66.3F+122 where OS is oxygen consumption in mg/h and F, the flow late in l/min (1 <F <5). The oxygen requirement of the system was calculated as the sum total of oxygen consumption of O. niloticus and of the oxygen requirement of the nitrifying bacteria for nitrification of excretory products from fish. The equation formula is as follows; OC= (1.41 W0.757+0.095W+1.83) n where OC is oxygen requirement in mg/h; W, the body weight in g (10 <W <250) and n, the number of fish. By mean of these equations, stocking limitation with O. niloticus in the system can be estimated. Therefore it is easy to find out the stocking density for long-term feeding experiment in the fishrearing closed tank.
