| Summary: | 碩士 === 國立臺灣大學 === 漁業科學研究所 === 104 === Most of land-based fish farming are freshwater aquaculture. In 2014, land-based aquaculture fish production has accounted for 64% of the total harvest of aquaculture. The aquaculture patterns have gradually become more intensive. The waste water which contains excess nutrients is disposed into the river. It may causes biological and environmental damage. The purpose of this study is to reduce the negative effect of Macrobrachium rosenbergii aquaculture by water-saving and energy-saving circulating water system. A 0.31 m3 biological filter and the 250 w low-power motor was set in the pond. We treat the bottom layer water of pond with the negative-pressure hydraulic system to purify the water. The area of this pond is about 1,400 m3 which can stock 15,000 shrimp. This system can purify about 23 m3 water per day. The hydraulic residence time of system is 14.5 minutes and the electricity is 9.4 NTD per day. That means the system can save more energy.
After 126 days, the maximum reduction rate of total ammonium nitrogen was 62.5%. The contamination of nitrate of output-water increased 23.7% compared with input-water. The dynamic of algal biomass was stable. Besides, the survival rates of shrimp in experiment and control group were 54% and 44%. The growth rates were 0.193 and 0.187 g/pic/day. And feed conversion ratio is 2.032 and 2.467. The growth index of shrimp in the experiment group is better than control group. This low-power system could reduce total ammonia, and increase nitrite and nitrate in the bottom layer of pond water. Therefore, algae can absorb nutrients efficiently and stabilize water quality. The system can enhance the effectiveness of aquaculture.
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