CAN THO UNIVERSITY COLLEGE OF AQUACULTURE AND FISHERIES ---------------------------- EFFECTS OF LIGHT INTENSITY ON FORMATION OF BIOFLOCS, WATER QUALITY, GROWTH PERFORMANCEOF WHITE LEG SHRIMP (Litopenaeus vannamei) POSTLARVAE IN SUPER INTENSIVE REARING TANK By PHAM THANH NHAN A thesis submitted in partial fulfillment of the requirements for The degree of Bachelor of Aquaculture Science Can Tho, December 2014 CAN THO UNIVERSITY COLLEGE OF AQUACULTURE AND FISHERIES ---------------------------- EFFECTS OF LIGHT INTENSITY ON FORMATION OF BIOFLOCS, WATER QUALITY, GROWTH PERFORMANCE OF WHITE LEG SHRIMP (Litopenaeus vannamei) POSTLARVAE IN SUPER INTENSIVE REARING TANK Supervisor Assoc Prof. PhD. TRAN NGOC HAI Dr. CHAU TAI TAO A thesis submitted in partial fulfillment of the requirements for The degree of Bachelor of Aquaculture Science Can Tho, December 2014 The thesis Effects of light intensity on formation of bioflocs, water quality, growth performance of white leg shrimp (litopenaeus vannamei) postlarvae in super intensive rearing tank defended by Pham Thanh Nhan, which was edited and passed by committee on 19th December, 2014. Sign of Advisor Dr. Chau Tai Tao Sign of Advisor Assoc Prof.PhD. Tran Ngoc Hai Sign of Student Pham Thanh Nhan EFFECTS OF LIGHT INTENSITY ON FORMATION OF BIOFLOCS, WATER QUALITY, GROWTH PERFORMANCE OF WHITE LEG SHRIMP (Litopenaeus vannamei) POSTLARVAE IN SUPER INTENSIVE REARING TANK Pham Thanh Nhan ABSTRACT This study aims to contribute to development of technology for nursing of white leg shrimp postlarvae in order to apply to practical production. A triplicated experiment was conducted at the hatchery of Can Tho University with 4 treatments of different light intensities of (1) not cover, (2) cover with 1 net layer, (3) cover with under 3 net layers; (4) no light. Composite tanks of 500 L containing 250 L of brackish water (15ppt) were used. White leg shrimp (PL15) were stocked at 2000 inds/m3. Strong aeration was applied. Wheat flour and soya bean meal were used at C/N ratio of 15:1. Water quality parameters (light intensities, temperature, pH, DO, Nitrite, TAN, Alkalinity) were checked weekly. Development and composition of bioflocs were also observed, measured and analyzed weekly. Shrimp growth was evaluated weekly and survival rate were recorded at the end of the nursing period of 1.5 month. The results indicated that light intensities have strong effects to water quality, bioflocs formation and composition and shrimp growth performances. Particularly, length and width of floc particles were in range of 0.15-0.38 mm and 0.09- 0.21 mm, respectively. Floc volume index continuously increased until the final week, reached to 13.7- 17.7 mL/L. Shrimp body length and body weight were largest in the treatment 2 (5.35cm and 1.4g) and lowest in the treatment 4 (4.5cm and 1.4g) after 1.5 months of nursing. The highest survival rate of 58.07 % and highest yield of 1.42 kg/m3 was also obtained from the treatment 2. The results show that the treatmen 2 with appropriate light intensity of 95-158lux gave the best results in water quality parameters and growth and survival of shrimp. Keywords: White leg shrimp, Litopenaeus vannamei, Bioflocs, light intensity 1 1. Introduction According to Viet Nam Directorate of Fisheries (2013), total white leg shrimp farming reached to 628,000 ha in areas and 258,780 tons in production. In the Mekong Delta, both white leg shrimp farming area and production have increased dramatically. However, shrimp farming have faced challenges such as bad quality post larvae, high investment cost, diseases, environmental pollution, etc. Therefore, the studies which aim to find out new and essential technology to control disease (EMS / AHPNS, WSSV, YHD,…) and environmental pollution, is very important for sustainable development of white leg shrimp farming. In recent years, biofloc is a new and potential technology that has been used in culture of different species such as carp, tilapia, giant freshwater prawn, and also white leg shrimp. Dense and active aerobic microbial communities are manipulated to control quality of the immobilization of ammonium of aerobic protein and in order to recycle feed residues, raise feed efficiency, reduce NH4+, NO2, water exchange, provide nature feed source, reduce feed cost, increase stocking density and ensure biosecurity (Avnimelech et al.,1989, 1992; Crab et all., 2007). There are a lot of studies about the effects of different stages, components of waste, factors affecting to Biofloc system and so on. Based on basis principal of Biofloc technology, difference in light intensities is also result in change Biofloc system. Therefore, evaluation the development and composition of bioflocs, rearing water quality, growth rates, survival rates and yields of white leg shrimp under different light intensities is main purposes of this study. Results of the study can contribute to the development of biofloc technology for rearing white leg shrimps from postlarvae to juvenile stages in order to apply to practical production. 2. Materials and methods 2.1 Experimental design The experiment was set up under the transparent plastic roof to get natural light. A tank system consisting of 12 tanks was used for 4 treatments, including treatment 1 (not cover – natural light), treatment 2 (cover with 1 layer nylon net), treatment 3 (cover with 3 layers nylon net), treatment 4 (cover with black plastic sheet - no light). Light intensity was measured by lightmeter. The experiment was completely randomized designed with three replications for each treatment. Tanks volume is 500 L, each tank was filled with 250 L water with 15-ppt brackishwater and stocked with 500PL/tank. Table 1:Biochemical composition in wheat flour and soybean meal ( % dry weight) Biofloc system was created by adding 8 g soybean meal and 2 g wheat flour per tank. Wheat flour and soybean mealwas heated in 60oC in autoclave, and incubated at room 2 temperature for 48 hours before adding to the tanks. It tooks 2 weeks to create biofloc system with Floc volume index (FVI) around 3 mL/L. After stocking shrimps, the same amount of wheat flour and soybean milt was supplied weekly. The experiment lasted for 6 weeks. Table 2: The amout of feed in experiment (g) No cover Feed 379 ± 64.2 1 layer nilon net 3 layers nilon net No light 839 ± 69.2 601 ± 129 591 ± 143 Post larvae were fed with commercial feed with 6 times/day and 0.5 g/day at the first 2 weeks. At 3rd and 4th, the amout of feed increased 1g/day and feeding 5 times/day. In last 2 weeks, shrimp also were fed 5 tiems/day with 2g/times. Weight of feed was calculated based on the average body weight at sample time, survival rate, uneaten feed and obervation from gut of shrimp. Thus, rate of feed fluctuated among treatments and days. Feed was stored in box and weight at the end experiment as table 2 2.2 Analytical methods Water quality parameters, light intensity, size floc particle, FVI, phytoplankton was measured weekly. Temperature was measured by thermometer. Nitrite and ammonium were tested by Serra test kits, Germany, DO was checked by YSP 556 , light intensity also check light intensity device, size floc and phytoplankton were observed on microscope, FVI was measured with Imhoff cones. Density of Vibrio spp, total bacteria and length, weight of shrimp was tested every 2 weeks. Vibrio spp were cultured in TCBS medium and total bacteria were cultured in TSA+ medium. At the end of experiment measured weight and length, calculated survival rate, FCR and Yield Data were analyzed about Mean, Standard deviation by Microsoft Excel 2010 and statistical differences by Statistics Package for the Social Sciences (SPSS 16.0). 3. Results and discussion 3.1 Light intensity Table 1: Light intensity during prepare biofloc and experiment (Lux) Prepare Biofloc No cover net Cover 1 layer net Cover 3 layers net Cover with black sheet (No light) Week 0 331.72 ± 26.6c 156.14 ± 119.8b 51.78 ± 32.9a 0 Week 1 296.18 ± 203.3c 107.72 ± 88.6b 45.82 ± 31.1a 0 Week 0 373.88 ± 228.9c 165.6 ± 126.2b 63.5 ± 38a 0 Week 1 335.86 ± 218.1c 149.56 ± 114.1b 63.72 ± 35.3a 0 Experiment 3 Week 2 320.34 ± 198.4c 139.36 ± 113.7b 55.88 ± 37a 0 Week 3 322.36 ± 274.6c 142.34 ± 111.5b 61.08 ± 49.1a 0 Week 4 318.46 ± 189.5c 122.38 ± 95.7b 54.58 ± 37.5a 0 a 0 a 0 Week 5 Week 6 c 283.9 ± 188.5 401.74 ± 256.5 c 96.74 ± 73.3 b 158.94 ± 122.4 56.06 ± 32.2 b 80.2 ± 48.9 Note: Value in the same row with different letters (a, b, c) are significantly different (p[...]... Conlusions and recommendations 5.1 conlusions: The treatment 2 (cover with 1 net layer) with light intensiy of 95-158lux gave the best results in water quality, biofloc formation and shrimp growth, survival and yield The treatment with no light gave the poorest water quality and shrimp performance, however it is comparable to the other treatments This is very promising for in- door culture of white leg. .. 2002a, Coastal water quality monitoring in shrimp areas: An Example from Honduras, Report of the World Bank, NACA, WWF và FAO consortium progam on Shrimp farmming and the Enviroment, Work progress for Public discussion, 29 pages, 7 Burford, M,A,, P,J, Thompson, P, McIntosh, R,H, Bauman, and D,C, Pearson, 2003, Nutrient and microbial dynamics in high -intensity, zero-exchange shrimp ponds in Belize, Aquaculture... layer) and lowest in the treatment with no light However, those were not significant among the treatments Figure 8 : Yield in treatments during experiment Generally, the results of the study indicated that light intensity has strong effect to water quality parameters, espcially on nitrite, alkality, algae, bacteria and shrimp growth performance The treatment 2 with light intensity of 95-158 lux gave... M.A., Thompson, P.J., McIntosh, R.P., Bauman, R.H., Pearson, D.C, 2003 Nutrient and microbialdynamics in high- intensity, zoo- exchange shrimp ponds in Belize, Aquaculture 219: 393- 411 9 Chamberlain, G.W, Hopkins, S.J, 1994 Reducing water use and feed cost in intensive ponds World aquaculture 25: 29- 32 14 10 Rittmann, B.E., McCarty, P.L 2001 Enviromental biotechnology- principles and appliations McGraw-Hill... activity of shrimp would affect to formation of floc particle (Ta Van Phuong et all, 2014) Figure 3: Size of floc particle during the experiment 3.3.2 Floc volume Index (FVI) Floc volume were low (2-4.3 mL/L) before stocking PL15 into tanks, However, there was a sharp rise of FVI after 1 week due to activities of shrimps, the amount of cassava and soybean meal supplied weekly and strong aeration (Ta... based upon a sequence of motivations, principles, and suitable operative technologies World Aquaculture 2011 Dept of Civil & Environmental Eng., Technion, Israel Inst of Technology Haifa, Israel 4 Anh, M T., 1989, Biological Characteristics and Technical prawn farming, Publishing House HCM city 5 Boyd, C E Thunjai, T., Boonyaratpalin, M., 2002 Dissolved salts in water for inland low-salinity shrimp. .. Rates of organic carbon and nitrogen degradation intensive fish ponds Aquaculture 211-216 2 Avnimelech Y., 2011 The development of bio-flocs technology (BFT) is based upon a sequence of motivations, principles, and suitable operative technologies World Aquaculture 2011 Dept of Civil & Environmental Eng., Technion, Israel Inst of Technology Haifa, Israel 3 Avnimelech Y., 2011 The development of bio-flocs... especially, development of Vibrio sp in treatment 1 and treatment 4 also inhibited shrimp s growth 10 Note: Value in the columns of the same week with different letters (a, b, c) are significantly different (p0.05)... significant difference among 4 treatments only first week of experiment The smallest sizes of floc particles were observed in treatment 2 (cover 1 layer net), followed by treatment 3 (cover 3 layer net) Suitable size of floc particles were smaller than 0.1 mm( Julie Ekasari et all, 2013) Observation of shrimp density in sampling days indicated that survival rates of shrimps in treatment 2 and treatment... Phuong et all, 2014) and it also continuously increased until the final week, reached to 13.7- 17.7 mL/L There was significant difference among 4 treatments in 0th , 1st , 6th week During experiment, treatment always had highest floc volume Based on research of Avimelech, optimal FVI for shrimp is 3- 15mL/L Generally, Floc volume in this study was in the optimal range 8 Figure 4: Floc volume index in