Studies Of The Artificial Substrates Applied In Intensive Shrimp Culture

In the early1990s, the artificial substrates had been used inaquaculture activities and researchers found that using artificial substratesin the water column could achieve some amazing effects such as goodwater quantity control effect, high shrimp survival rate, low feedconversion rate and high bio-security etc. Also, adding artificialsubstrates in shrimp culture are some points of pursuing an economically,environmentally and sustainably rearing mode. This dissertation mainlystudy: the methods of improving the hydrophilicity of the artificialsubstrates, studies of the artificial substrates applied in winter indoorzero-water exchange culture system and effects of artificial substrates onbacterial communities in shrimp culture ponds. The main results wereshowed as follows:1Effects of six modifiers to the hydrophilicity of the artificial substratesThe aim of this study is to discuss the correlate treatment parametersof modifiers in the in-situ aquaculture wastewater treatment processthrough enhancing the hydrophilicity of the biofilm-substrate, promotingthe mature of the membrane, thus provide references to the applicationinto the prawn aquaculture wastewater treatment process. The silk net(#40) and six mofifiers (NaOH, Ca(OH)2, HCl, KMnO4, K2Cr2O7,C2H5OH) were chosen as the biofilim-substrate, the substrate surfacemodification treatment reagent, respectively. The statistics of Bacillus spp.adsorb amount and membrane-hanging results which provide some keyevaluation indexes of the six modifiers. The results showed that, comparing with other treatments, the10%HCl treatment got the bestsubstrate hydrophilic ability and better membrane formation effect.2Studies of the artificial substrates applied in winter indoor zero-waterexchange culture systemTrials were conducted to examine the effects of using artificialsubstrates on water quality and the shrimp growth performance in thezero-water exchange Litopenaeus vannamei culture system. The resultdemonstrates: during the whole experiment period, the treatment grouppresented a better water quality than the control group. The averageammonia and nitrite-N concentrations in treatment group were significantlower than the control group (P<0.05). Also, the amounts of totalheterotrophic bacteria and the vibrio spp. were significantly lower in thetreatment group (P<0.05). The survival rate in the test group was average84.9%, the special growth rate was4.69%and the production was0.74kgm-2which were all greater than control (P<0.05). Significantly lower feedconversion rate (1.1) was presented in the treatment group than thecontrol group (P<0.05). Final shrimp weight in treatment group reached3.81g which was higher than the control group, but not significant(P>0.05). Researches indicate that the utilization of artificial substrates inindoor shrimp culture system could effectively control the water quality,greatly improve the shrimp survival rate and the growth rate, significantlyreduce the feed conversion rate and lead to an increase in the shrimpproduction indeed.3Effect of artificial substrates on bacterial communities in shrimp culturepondsWe had monitored and investigated the bacterial communitycomposition in the substrate-biofilm shrimp culture system by denaturinggradient gel electrophoresis (DGGE). By analyzing the sequences of the18dominant microbial community bands of the culture water find that: uncultured Firmicutes (Bacillus spp.), account for44.4%of total species,uncultured Proteobacteria, account for16.7%of total species, in which5.6%is α-Porteobacteria and the rest is β-Porteobacteria (11.1%),uncultured Actinobacterium, account for11.1%, the rest are unculturedbacterium, account for27.8%of total species. Uncultured Firmicutes(Bacillus spp.) is the most dominant bacterial which can be seenthroughout the rearing periods. UPGMA clustering analysis shows thatthe bacterial species in substrate treatment gather together and the sameas in control treatment. Phylogenetic analysis indicates that the dominantmicrobial populations occurred alternately in both treatments at thedifferent sampling time, indicates that the dominant microbialcommunities composition of bacteria in the culture water was lessinfluenced by the artificial substrate.