Nitrogen Excretion of Epinephelus coioides in Aquaculture pond

Grouper are common aquaculture species in Taiwan, not only has the characteristics of high economic value, but also by the people loved. At present, the main way to keep the water clean is to pump a large number of water from coastal waters, in order to reduce pumping electricity energy expenditure and reduce the risk of water pollution, the design of a suitable system and circulating water treatment equipment, and understand the cultured fish nitrogen emission rate is the primary goal. In this experiment, we use 8 inches (about 300 grams) of grouper fish as experimental. After feeding stop for two days, the fast of total nitrogen excretion includes total ammonia nitrogen (TAN) and total ammonia. The results show, the average of nitrogen excretion rate of fast was 7.16 ± 0.45 mg L-1; wherein the solid nitrogen is 1.06 ± 0.28 mg L-1, liquid nitrogen was 6.09 ± 0.73 mg L-1. the concentrate of solid nitrogen is about 6 times more than liquid nitrogen (TAN), accounting for 85.1% of liquid nitrogen, solid nitrogen 14.9%. The average of TN emission rate for the fasting is 96.80 mg kg-1h-1, its solid-liquid ratio of 13.38. And 24 hours after the feeding experiments, the average emission rate of total nitrogen was 104.23 ± 82.62 mg kg-1h-1. The maximum emission rate of total nitrogen after feeding occurs in the first 0-4 hours. At least 8 hours after the total nitrogen discharge rate after feeding was also leveled off. Compare the light phase and dark phase, the total nitrogen emission rate of light phase is higher than dark phase, the average total ammonia emission rate of light phase is 4.85 mg L-1 h-1,and the average rate of total ammonia emissions in dark phase is 1.22 mg L-1 h-1. It can be applied when the transport of live fish, dark environment helps slow the delivery process caused by the deterioration of water quality. In this experiment, the trap as a tool to capture the solids are not only captured feces but also contains mucus from grouper, although it will not be leaving the ammonia dissolved in water concentration increased in short-term, but it is a good breeding place for bacteria and many viruses, so it’s better to remove solid particles effectively, to avoid the breeding of pathogens in water to provide a future reference design and optimization of farming systems.