Primary Studies On Integrated Culture Of Litopenaeus Vannamei, Scatophagus Argus And Ipomoea Aquatic

Integrated Multi-Trophic Aquaculture (IMTA) is an ecological and economicfarming strategy that minimizes waste from culture systems, reduces the risk of diseasesand provides an additional income source. An integrated culture system of white shrimp(Litopenaeus vannamei), spotted scat (Scatophagus argus) and water spinach (Ipomoeaaquatic) was set up, combining with biofloc technology, to evaluate the effects of addingmaize starch on the yield, water quality, nutrient recovery and economic return in theIMTA system. The main results of this study are shown as follows:1. To investigate the effects of different densities and sizes of spotted scat onproduction and nutrient recovery in integrated culture（IMTA） system of white shrimp,spotted scat and water spinach, an experiment was conducted using a3×2factorialdesign in21outdoor cement tanks (5×3×1.2m). Combinations of two kinds of sizes(10.0,30.0g fish-1) and three kinds of densities (1,2and3fish m-2) of spotted scat wereset, while three additional tanks with shrimp monoculture were used as a control. Therewas no water exchange and feed input to all treatments was limited to the same amount.In comparison with monoculture, IMTA model increased the shrimp survival rate, totalbiomass and combined overall FCR remarkably. The combined nutrient recovery inIMTA tanks was significantly higher than in single shrimp tanks (P<0.05), ranging from44.4%to62.5%for total nitrogen and from19.4%to29.1%for total phosphorous. Theoptimal stocking density and size of spotted scat was2or3fish m-2and30.0g fish-1.2. A trial was conducted to evaluate the effects of adding maize starch on the yield,water quality and formation of bioflocs in an IMTA system comprising white shrimp, spotted scat and water spinach. Shrimp were randomly assigned to one of fourtreatments (T1, T2, T3and T4) and reared in monoculture (T1) without the addition ofstarch, or in polyculture (with spotted scat and water spinach) with (T3and T4) orwithout (T2) the addition of starch. Shrimp in T1, T2and T3were fed three times dailywith an equal amount of commercial pellets, while shrimp in T4were fed at80%of thefeeding amount of other treatments. Shrimp survival was higher in T3and T4(95.6%and94.3%, respectively) than in T1and T2(51.1%and56.5%, respectively)(P<0.01).The shrimp yield was highest in T3(0.495kg m-3), which also had the lowest feedconversion ratio (1.02). The specific growth rate was higher in T1(1.61%) than in T4(1.17%)(P<0.01). T3had the best economic performance among all treatments, andsignificantly better than T1(P<0.01), T2and T4(P<0.05). The levels of nitrite-N(NO2-N) were significantly lower in T3and T4at the end of the experiment than inother treatments (P<0.01). Similarly, total ammonia nitrogen (TAN) was lower and totalsuspended solids (TSS) was higher in T3and T4than in T1and T2(P<0.05). The levelof chlorophyll a (Chl a) was significantly higher in T1than in other treatments (P<0.05).The biofloc volume was highest in T3(10.84ml)(P<0.01) and the crude protein contentof bioflocs ranged from8.7%to24.0%. The results suggested that the addition of starchinto the IMTA system of shrimp, spotted scat and water spinach improved productivity,profitability and water quality. The combination of the IMTA model and biofloctechnology had a synergistic effect on overall FCR and economic return, and was moreeffective at improving shrimp survival, production and reducing nitrite-N and TAN thanuse of the IMTA model alone.3. To investigate the effects of the combination of biofloc technology and the IMTAmodel of white shrimp, spotted scat and water spinach on economic return and nutrientrecovery, an experiment was carried out under the experiment condition of chapter3. T3had the best economic performance among all treatments, and significantly better thanT2and T4(P<0.05), while the IMTA treatments had significantly better economicreturn compared with T1. The culture species in the treatments with starchsupplementation (T3and T4) had significantly higher nutrient recovery than in othertreatments (P<0.05), while nutrient recovery in T2were significantly higher than inT1(P<0.05).