The Research And Application Of Biological Floc Technology In The Cultivation Of Broodstock Penaeus Monodon

Penaeus monodon is one of the world’s three major species farmed shrimp; it has an important economic value as the largest individual in Penaeus. Although the artificial reproduction techniques of P. monodon have successed, however, the high health broodstock full-scale artificial breeding techniques are still not completely resolved. It has special significance for establishment of high health breeding improved system of P. monodon to development of shrimp farming planting controlled environmental conditions. It is need more than 10 months to nurturing P. monodon Broodstock. The affected of natural weather condition such as heavy rain, typhoons, heating and cooling changes and others in traditional broodstock farming system is still large. It’s easily leads to the broodstock stress response, and it’s not conducive to broodstock cultivation management. Raising shrimp raising water first, how to effective long-term control and protection of good and stable water quality in broodstock farming system is particularly important.Bio-floc technology provides a new solution idea for the above problems and conceived. Bio-floc technology can promote a large number of heterotrophic bacteria multiply by regulatory the ratio of C/N in water. The reproduction and transformed into bacterial protein of heterotrophic bacteria and other microorganisms can effectively remove contaminants in the water by absorbing and transforming excrement by fish and shrimp. Shrimp ingestion the floc by flocculation can achieve secondary use of the feed. This technique depends on heterotrophic bacteria multiply. The biological floc technology will be applied to the P. monodon broodstock farming system in this paper. The goal is to study the biological floc formation conditions in P. monodon farming system; wether the biological floc technology can be used at different growth stages of P. monodon and the structural differences of microbial colinies in water between different farming methods. Provide basic theory and practical guidance for the application of biological floc technology to P. monodon broodstock cultivation by explores changes in the growth characteristics of P. monodon and the parameters of water under the conditions of biological floc technolegy.1. Biological floc formation conditions and effects:In order to determine the optimum carbon source and dosage to form the bio-floc in P. monodon culture systems, the first study select three kinds of carbon source (glucose, sucrose and molasses) added in the culture system at C/N of 20. And select the sucrose is the optimum carbon source, and then adds sucrose in the culture systems at daily ration of 0,25,50,75,100%. The results show:(1) Three different carbon sources all can significantly increase the SGR of P. monodon (P<0.05). Sucrose can significantly increase the survival rate of P. monodon (P<0.05). (2) Compared with other groups add 75% of the sucrose can significantly improve P. monodon SGR and SR (P<0.05). It also can promote heterotrophic bacteria and phytoplankton reproduction, and the concentration of harmful substances in water such as NH4-N; NO2-N et al are lower, but add excessive sucrose will be counterproductive. The results showed that 75% of sucrose added is the most suitable condition for bio-floc formation in P. monodon systems. And promote the growth of the P. monodon.2. Aquaculture water quality influenced by sucrose added in 24h:In order to determine water quality and various biological indicators changes after sucrose added in aquaculture water, the study measuring each index changes every 4h inorder to obtain the variation of each index. The results showed that:The concentration of NO3-N has the most obvious changes in various water quality indicators in biological floc group after sucrose added compared with the control group. And the changes are basically the same at the concentration of NH4-N、NO2-N、PO43--P and biological floc group are less than the control group. Chl-a concentrations peaked 389.12 μg/L in biological floc group at 18:00, and heterotrophic bacteria reached a peak after 8h of sucrose added, and adding sucrose will reduce the pH of water. The results showed that the multiply of heterotrophic bacteria and algae can role play to improve water quality by assimilate NH4-N and other harmful substances in the water.3. The affect of three kinds of farming methods on growth and survival of different sizes P. monodon and water quality:To determine whether the biological floc technology is suitable for different specifications of P. monodon, the study select 3 different specifications P. monodon (1g、20g、40g)cultured in 3 kinds of farming methods (algae, water changes, biological floc). The results show:1. Shrimp growth and survival. The SGR and SR in biological floc group were significantly higher (P<0.05) than the algae group, while no significant difference (P> 0.05) compar with water changes group, and relative fatness and FRC in biological floc group were significantly higher than the other two groups (P<0.05) in 1g P. monodon aquaculture system. The SGR in biological floc group was significantly higher than the water changes group, while the algae group had no significant difference (P>0.05) compar whit the other two groups, and the SR was 23.33% higher than the water changes group significantly higher than the other two groups (P<0.05), and relative fatness had no significant difference in three groups (P>0.05) in 20g P. monodon aquaculture system. The SGR and SR in biological floc group and water changes group were significantly higher than algal group (P<0.05), the highest SGR was the water changes group and the highest SRwas the biological floc group, and elative fatness had no significant difference in three groups (P> 0.05) in 40g P. monodon aquaculture system.2. Water quality:The concentrations of NH4-N、NO2-N、NO3-N、PO43--P in algae group were higher than the other group, the number of heterotrophic bacteria and Bacillus is much larger than the other two groups, the concentrations of Chl-a in algae group only appeared significantly at the latter part in 1g P.monodon aquaculture system. Every water quality indicators in 3 groups’changes instability, the specific performance were that the concentrations of NH4-N、NO2-N、NO3-N、PO43--P in algae group were relatively low-at early stage, while every index in water changes group was higher than the other two group especially the concentration of NH4-N reached 1.378 mg/L, every indexe in 3 group had the most obvious changes at the latter part especially the concentration of NO2-N in algae group continued to rise until September 20 reached 0.412 mg/L in 20g P.monodon aquaculture system. The results showed that, the most beneficial farming method was the biological floc technology in 1 and 20 g P.monodon aquaculture system. While water changes group and biological floc group had their own advantages, the biological floc technology is the best choice relative to water conservation, P.monodon healthy breeding and maneuverability in 40g P.monodon culture system.3. Microbial community structure analysis of water by three kinds of farming methods: To compare the differences of microbial communities in water between three kinds of farming methods, the study select microorganisms in water about 3 kinds of farming methods (algae, water changes, biological floc) that cultured P. monodon of weight 20g. The experimental taken water samples every 15d to analyze structural characteristics of microbial colonies by using PCR-DGGE. The results show that:The bacterial diversity of biological floc group were higher than the other two groups throughout the culture cycle, and the main advantages of bacteria in each experimental group were α-proteobacteria such bacteria plays a vital role in nitrogen, phosphorus cycle in the ecosystem. The opportunistic pathogen of Acinetobacter only appeared in the algae group at the early culture stage, while the opportunistic pathogen Vibrio were not there in each group. The results showed that: Carbon source added conducive to increasing the diversity of microbial communities in the water. It can effectively promote the propagation of beneficial bacteria and inhibit the breeding of harmful bacteria that supplemented by bio-floc technology in P.monodon culture system.