Tài liệu Effects of magnesium-phosphorus-potassium containing in water on molting, growth and survival rate of the white shrimp (litopenaeus vannamei) juveniles, reared in low salinity water

CAN THO UNIVERSITY COLLEGE OF AQUACULTURE AND FISHERIES EFFECTS OF MAGNESIUM-PHOSPHORUS-POTASSIUM CONTAINING IN WATER ON MOLTING, GROWTH AND SURVIVAL RATE OF THE WHITE SHRIMP (Litopenaeus vannamei) JUVENILES, REARED IN LOW SALINITY WATER By TRAN THI BE GAM A thesis submitted in partial fulfillment of the requirements for the degree of Bachelor of Aquaculture Can Tho, 12/2013 CAN THO UNIVERSITY COLLEGE OF AQUACULTURE AND FISHERIES EFFECTS OF MAGNESIUM-PHOSPHORUS-POTASSIUM CONTAINING IN WATER ON MOLTING, GROWTH AND SURVIVAL RATE OF THE WHITE SHRIMP (Litopenaeus vannamei) JUVENILES, REARED IN LOW SALINITY WATER By TRAN THI BE GAM A thesis submitted in partial fulfillment of the requirements for the degree of Bachelor of Aquaculture Supervisor MSc. HUYNH TRUONG GIANG Can Tho, 12/2013 ACKNOWLEDGEMENT Foremost, I would like to express my sincere gratitude to my supervisor, MSc. Huynh Truong Giang for the continuous support of my study, for his invaluable guidance, advice, encouragement, and immense knowledge. His guidance helped me in all the time of research and writing of this thesis. I want to dedicate my great appreciation to Ms. Phan Thi Cam Tu for her kind help in finishing the research. Many thanks are also giving to all other doctors of the college of aquaculture and fisheries, and especially to those of the Department of Applied Hydrobiology for providing me with great working and learning conditions. I would love to express my sincere appreciation to many of my friends, especially Pham Thi Trang Nhung, Le Phuoc Dai, Bui Doan Luan, and Tran Trung Giang for their unconditionally kind help throughout the experimental period. Last but not the least, I really want to thank my family for their great life-time support which makes everything possible for me. Tran Thi Be Gam i APPROVEMENT The thesis “Effect of Mg-P-K levels containing in water on molting, growth, and survival rate of the white shrimp L. vannamei juveniles, reared in low salinity water” was completed base on my results. Supervisor’s signature Student’s signature ii ABSTRACT The objective of the present study was to evaluate the effects of several aqueous magnesium, potassium, and phosphorus on survival, growth, and molting interval of L.vannamei at salinity 2‰. The study consisted of two experiments. The study consisted of two experiments. For the first experiment with postlarvae 15-day, aqueous Mg-K-P were supplemented directly into water at three different levels (10-5-5; 20-1010; 40-20-20 mg/L) and a treatment with no supplemented minerals severed as the control group. In the second experiment, concentrations of minerals added in the treatments were the same as the first experiment but conducted with juvenile shrimp (4.7±0.02 g). Each treatment comprised of 14 shrimp. Each shrimp was individually cultured in a small net cage. Fourteen small net cages were allocated in a composite tank with a capacity of 1 m3. Molting interval, survival, growth rate were recorded. Results from the first experiment indicated no significant differences (p>0.05) in survival and growth of shrimp among treatments. Results from the second experiment reveal a significant difference in survival between 10-5-5 treatment (14.29%) and all other treatments (28-36%). The results showed highest weight gain (1.7±0.27 g), length gain (1.81±0.29 cm), SGR (1.71±0.35% day-1) and DWG (0.08±0.016 g day-1) in 20-10-10 treatment. However, no differences in molting interval were observed. These results suggest supplementation of mineral are common in low salinity water. Keywords: Litopenaeus vannamei, low salinity, magnesium, phosphorus, potassium, molting. iii TABLE OF CONTENTS Pages ACKNOWLEDGEMENT ............................................................................................i APPROVEMENT........................................................................................................ii ABSTRACT .............................................................................................................. iii TABLE OF CONTENTS............................................................................................iv LIST OF TABLES.....................................................................................................vii LIST OF FIGURES ..................................................................................................viii LIST OF FIGURES ..................................................................................................viii LIST OF ABBREVIATIONS .....................................................................................ix LIST OF ABBREVIATIONS .....................................................................................ix Chapter 1 .....................................................................................................................1 INTRODUCTION .......................................................................................................1 1.1 Problem identification: .......................................................................................1 1.2 Objective:...........................................................................................................2 1.3 Research content: ...............................................................................................2 Chapter 2 .....................................................................................................................3 LITERATURE REVIEW ............................................................................................3 2.1. Biological characteristics of white shrimp (Litopenaeus vannamei):..................3 2.1.1. Classification: .............................................................................................3 2.1.2. Distribution:................................................................................................3 2.1.3. Life cycle:...................................................................................................3 2.1.4. Growth characteristics: ...............................................................................4 2.1.5. Molting cycle:.............................................................................................4 2.1.6. Nutrition demand:.......................................................................................6 iv 2.2 Osmoregulation of shrimp ..................................................................................7 2.3 Effect of low salinity on the growth and survival rates of white shrimp (L.vannamei) ............................................................................................................8 2.4 White shrimp (L. vannamei) production in the world:.........................................8 2.5 White shrimp (L. vannamei) production in Vietnam: ..........................................9 Chapter 3 ...................................................................................................................10 MATERIALS AND METHODS ...............................................................................10 3.1 Time and location.............................................................................................10 3.2 Materials ..........................................................................................................10 3.2.1. Shrimp culture ..........................................................................................10 3.2.2. Equipment and chemicals .........................................................................10 3.3 Research design and experimental approaches..................................................10 3.3.1 Experiment 1: Effects of Mg-P-K supplemented in water on growth and survival rate of white shrimp (L. vannamei)........................................................10 3.3.2. Experiment 2: Effects of Mg-P-K supplemented on molting intervals of white shrimp L. vannamei (4-5 g) that reared in low salinity water .....................12 3.4 Data analysis ....................................................................................................13 Chapter 4 ...................................................................................................................14 RESULTS AND DISCUSSIONS ..............................................................................14 4.1 Experiment 1: Effects of Mg-P-K supplemented in water on growth and survival rate of white shrimp (L. vannamei).........................................................................14 4.1.1 Water quality .............................................................................................14 4.1.1.1 Temperature (oC) and pH.....................................................................14 4.1.1.2 Total ammonia nitrogen (TAN), Nitrite (N-NO2-), and Phosphate (PPO43-)..............................................................................................................14 4.1.1.3 Calcium (Ca2+), Magnesium (Mg2+), Potassium (K+) concentrations and Mg:Ca ratios................................................................................................................15 v 4.1.2 Growth performance ..................................................................................16 4.1.2.1 Weight Gain (WG), Daily Weight Gain (DWG), Specific Growth Rate (SGR) .............................................................................................................16 4.1.2.2 Length Gain (LG), Daily Length Gain (DLG), Specific Growth Rate (SGR) .............................................................................................................17 4.1.3 Survival rate (%)........................................................................................17 4.2 Experiment 2: Effects of Mg-P-K supplemented on molting intervals of white shrimp L. vannamei that cultured in low salinity water...........................................19 4.2.1 Water quality .............................................................................................19 4.2.1.1 Temperature, pH..................................................................................19 4.2.1.2 Total ammonia nitrogen (TAN), Nitrite (N-NO2-), Phosphate (P-PO43-) ........................................................................................................................19 4.2.1.3 Calcium (Ca2+), Magnesium (Mg2+), Potassium (K+), and Mg:Ca ratios ........................................................................................................................20 4.2.2 Growth performance of white shrimp L. vannamei ....................................21 4.2.2.1 Molting intervals of white shrimp L. vannamei....................................21 4.2.2.2 Weight gain of white shrimp after molting ..........................................22 4.2.2.3 Length gain of white shrimp after molting...........................................23 4.2.2.4 Growth performance of white shrimp at the end of experiment............24 4.2.2.5 Survival rate ........................................................................................25 Chapter 5 ...................................................................................................................27 CONCLUSIONS AND RECOMMENDATIONS......................................................27 5.1 Conclusions......................................................................................................27 5.2 Recommendations ............................................................................................27 REFERENCES ..........................................................................................................28 vi LIST OF TABLES Table 1: Events of possible technological significance occurring in the molting cycle of shrimp .....................................................................................................................5 Table 2: Ionic composition of seawater and freshwater ................................................7 Table 3: Production of white shrimp in North, Central and South of Viet Nam in 20099 Table 4: Methods for water quality sampling and analysis .........................................11 Table 5: Temperature and pH in Experiment 1...........................................................14 Table 6: TAN, N-NO2- and P-PO43- in Experiment 1 .................................................15 Table 7: K+, Mg2+ and Ca2+ concentrations in Experiment 1 ......................................15 Table 8: Hardness and Mg:Ca ratios for white shrimp reared in low salinity water in Experiment 1 .............................................................................................................16 Table 9: Growth performance indices of white shrimp L.vannamei that reared in salinity 2‰ with different Mg-K-P supplemented levels in Experiement 1. ...............17 Table 10: Initial length (cm), final length (cm), daily length gain (cm day-1), specific growth rate (% day-1), and length gain (g) for L.vannamei reared in salinity 2‰ in Experiment 1 .............................................................................................................17 Table 11: Temperature and pH in Experiment 2.........................................................19 Table 12: TAN, Nitrite, and Phosphate for white shrimp reared in low salinity water in Experiment 2 .............................................................................................................20 Table 13: Potassium, magnesium, and calcium for white shrimp reared in low salinity water in Experiment 2................................................................................................20 Table 14: Hardness and Mg:Ca ratios for white shrimp reared in low salinity water in Experiment 2 .............................................................................................................21 Table 15: Weight gain (g), daily weight gain (g day-1), specific growth rate (% day-1 ) of shrimp reared in low salinity water in Experiment 2 ..............................................25 Table 16: Length gain (cm), daily length gain (cm day-1), specific growth rate (% day1 ) of shrimp reared in low salinity water in Experiment 2...........................................25 vii LIST OF FIGURES Fig. 1: White shrimp (Litopenaeus vannamei)..............................................................3 Fig. 2: Life cycle of Litopenaeus vannamei..................................................................4 Fig.3. Net cage used in Experiment 2.........................................................................13 Fig.4: Survival rate (%) of shrimp that reared in low salinity (2‰) at different Mg-K-P supplements. Each bar represents the mean value from 3 replicates with a standard error...........................................................................................................................18 Fig.5: Molting intervals of white shrimp (L.vannamei) ..............................................22 Fig.6: Weight gain of L.vannamei after molting.........................................................22 Fig.7: Mean weight of shrimp after each molting.......................................................23 Fig.8: Length gain of L.vannamei after each molting .................................................23 Fig.9: Mean length of shrimp after each molting........................................................24 Fig. 10: Survival rate (%) of shrimp in Experiment 2.................................................26 viii LIST OF ABBREVIATIONS L.vannamei Litopenaeus vannamei Mg Magnesium P Phosphorus K Potassium Ca Calcium Ex. Experiment Trt. Treatment MT Metric tons TAN Total ammonia nitrogen FAO Food and Agriculture Organization NO2- Nitrite Fig.: Figure Wt. Weight Lt. Length WG Weight gain LG Length gain DWG Daily weight gain DLG Daily length gain SGR Specific growth rate ix Chapter 1 INTRODUCTION 1.1 Problem identification: White shrimp (Litopenaeus vannamei) had been exploited and appeared on the consumer market of the United State since 1709. Currently, they are widely cultured in countries of Asia-Pacific. The introduction of white shrimp to Asia has given rise to a bloom in farming of this species in China, Thailand, Indonesia and Viet Nam in the last decade, resulting in an almost complete shift from the native black tiger shrimp (Penaeus monodon) to this introduced species in Southeast Asia. In the year 2010, global aquaculture for this species reached 2.7 million metric tons (MT) (FAO, 2012). In Viet Nam, cultivation of white shrimp L. vannamei culture has been growing rapidly and become an important economic activity in Mekong Delta. In fact, white shrimp production has been increasing since 2000 and the export value reached 676.6 million USD (177,817 MT) in 2012 (VASEP, 2013). There are many problems which farmer needs to care for culturing white shrimp. Requirement nutrients of white shrimp, especially minerals, are most important. Around twenty-two minerals, both macro and micro, have been found essential to animals, fish and shrimp. However, unlike fin-fishes, there is relatively fewer information on the mineral needs of shrimps. Most of the information available for mineral requirements has been done under laboratory conditions using purified or semi-purified diets and scanty information is available on elemental requirements under practical culture conditions (Tacon, 1987). White shrimp L. vannamei has rapid growth, short molting cycle cause high demand minerals. Molting, especially, is fundamental for growth in shrimps. Shrimp generally lose most of their body content of minerals during molt and replace it from the water. White shrimp live in an environment that is hypertonic and continually drink small amounts of water and thus they can absorb some minerals directly from the water via the gills, skin or both (Tacon, 1987). Although minerals are very important, the study of mineral requirements of white shrimp has been quite neglected. Besides that, the ability of white shrimp L.vannamei to tolerate a wide range of salinities (0.5-40 ‰) has made it a popular species for low salinity culture. However, in low salinity water, problems still arise from deficiencies in minerals of pond water. Therefore, direct supplementation of macro-minerals as magnesium, phosphorus, and potassium in the water instead of food are of primary concern. In this study, molting stage durations, growth performance indices and survival rate of white shrimp L. vannamei were examined. 1 1.2 Objective: This study was undertaken on L.vannamei to evaluate the effect of Mg-P-K levels containing in low salinity water in molting cycle, growth, and survival rate in order to propose potential use for white shrimp L. vannamei culture in low salinity area in Mekong Delta. 1.3 Research content: - Research on effects of different Mg-P-K levels on growth and survival rate in white shrimp L. vannamei postlarvae. Research on effects of different Mg-P-K levels on molting intervals of white shrimp L. vannamei juveniles. 2 Chapter 2 LITERATURE REVIEW 2.1. Biological characteristics of white shrimp (Litopenaeus vannamei): 2.1.1. Classification: Phylum: Arthropoda Subphylum: Crustacea Class: Malacostraca Order: Decapoda Family: Penaeidae Genus: Litopenaeus Species: L. vannamei Fig. 1: White shrimp (Litopenaeus vannamei) (Source: www.fao.org) 2.1.2. Distribution: The white shrimp is native to the Eastern Pacific coast from Sonora, Mexico in the North, through Central and South America as far South as Tumbes in Peru, in areas where water temperatures are normally >20 °C throughout the year. White shrimp L. vannamei live in tropical marine habitats (FAO, 2006). 2.1.3. Life cycle: Adult Litopenaeus vannamei spawn in the ocean, releasing their eggs into the water. The eggs hatch into a non-feeding nauplius larva, which lasts about two days, before molting into a zoea stage (4-5 days), a mysis stage (3-4 days) and a postlarva (10-15 3 days) (Barnes 1983; FAO, 2011 – stage durations are given for unspecified aquaculture conditions). Postlarvae and juveniles tend to migrate into estuaries, while adults return to the sea for spawning (FAO, 2011). Fig. 2: Life cycle of Litopenaeus vannamei (Bailey-Brock and Moss, 1992) 2.1.4. Growth characteristics: Males become mature from 20 g and females from 28 g onwards at the age of 6–7 months. L. vannamei weighing 30–45g will spawn 100,000–250,000 eggs of approximately 0.22 mm in diameter. Hatching occurs about 16 hours after spawning and fertilization. The first stage larvae, termed nauplii, swim intermittently and are positively phototactic. Nauplii do not feed, but live on their yolk reserves. The next larval stages (protozoea, mysis and early postlarvae respectively) remain planktonic for some time, eat phytoplankton and zooplankton, and are carried towards the shore by tidal currents. The postlarvae change their planktonic habit about 5 days after molting into postlarvae, move inshore and begin feeding on benthic detritus, worms, bivalves and crustaceans (FAO, 2012). 2.1.5. Molting cycle: Molting in shrimp is a phenomenon that always occurs in the process of shrimp culture. The size of shrimp meat grew while the outer shell does not grow large, so for the adjustment, the shrimp will release the old shell and reshape a new shell with conducted by calcium. This molting process resulted in increased body size periodically. After a hard outer shell, shrimp body size remains until the next molting cycle. Duration of the molting cycle depends on the species and age of the shrimp. Molting frequency on white shrimp decreased along with increasing the size of shrimp. The larval stage, the white shrimp molting every 40 hours at 28 oC while juveniles 4 weighing 1-5 g, molting every 4-6 days. The next on the weight of 15 g, the period of molting occurs every 2 weeks (Cortell, 2012). Molting phase is the most important phase for shrimp, because at this phase, the shrimp in a most weak condition and not yet hardened outer shell layer, so making it very susceptible to diseases infection and attacked by other shrimps (cannibalism) and predators. Besides susceptible to diseases and predators, in molting phase, the shrimps are also very vulnerable to environmental changes, whether environmental changes that occur in ponds and the changes that occur because of weather changes. Shrimp have to face the pervasive influence of the molt cycle on their internal environment during their entire life cycle (Passano, 1960; Bliss, 1985; Garcia, 1988; Franco et al., 2006). Table 1: Events of possible technological significance occurring in the molting cycle of shrimp (Cobb and Bryant F, 1977) Stage of molt Status of cuticle Events Postmolt Initially soft becoming increasingly harder - Continued water absorption Intermolt Hard - Tissue growth begins - Main tissue growth - Accumulation of melanin precursor (storage form of N-acetyldopamine) and other organic reserves Premolt Hard but gradually thinned - Epidermal and hepatopancreas activation - Activation of Nacetyldopaamine precursor - Epicuticle formation begins utilizing N-acetyldopamine - Major portion of skeletal re-absorption - Ecdysial sutures open Molt Soft 5 - Beginning water absortion 2.1.6. Nutrition demand: - Protein: Protein, which is required for growth and maintenance, is an expensive component in a diet. Salinity also is among the factors known to influence the protein requirement of shrimp (Boonyaratpalin, 1996). Some studies comparing the optimum dietary protein level for shrimp. For juveniles, Colvin and Brand (1977) reported less than 30% to be the protein requirement while Kureshy and Davis (2002) found a maximum protein requirement at 32% for juveniles and sub-adults of L. vannamei. The first report of protein requirement for post-larvae, raised in tanks during one month (Colvin and Brand, 1977), indicated 30-35%. - Phospholipids and cholesterol are two essential lipids for penaeid shrimp. Cholesterol is an essential lipid that is closely involved in the process of molting in shrimp (Kanazawa et al. 1975) and is important in enhancing shrimp growth (Gong et al. 2000). Phospholipids may be contributive to facilitating molting process as well. Cholesterol requirement can be lowered as dietary phospholipid level increases. A combination of 0.05% cholesterol and 5% phospholipid is recommended for intensive L. vannamei culture (Gong et al., 2001). - Minerals: Marine shrimps absorb minerals from their aquatic environment aside from the minerals that come from the food they eat (F. Piedad-Pascual, 1989). Minerals are essential components of bones, teeth, fin, and exoskeleton. These are necessary for maintenance of osmotic pressure, acid-base balance, thus the regulation of pH of blood, haemolymph, urine, and other body fluids. They are also components of soft tissues, enzymes, some vitamins, hormones and respiratory pigments and are essential for muscle contraction and transmission of nerve impulses (Davis, 1996). Shrimps need minerals for growth because of repeated molting wherein minerals are lost (Kanazawa, 1985).  Phosphorus: Phosphorus is an element shrimp cannot find in reasonable amount in seawater. In contrast to calcium, phosphorus has to be added to the diet, but according to the pH of the anterior part of the stomach differences are expected in relation to the nature of the phosphate salt (Velasco et al., 2001). As a component of these important biological substances, phosphorus plays a central role in energy and cell metabolism.  Magnesium: magnesium plays a role in the normal metabolism of lipids, proteins, and carbohydrates serving as a cofactor in a large number of enzymatic and metabolic reactions (Davis and Lawrence, 1997). Seawater typically contains high levels of magnesium is excreted by marine crustacean and fish, resulting in blood levels lower than of the external medium (Dall and Moriarty, 1983). Cheng et al. (2005) reported a dietary Mg2+ requirement for 6 optimal growth of 2.6-3.46 g Mg2+ kg-1 for L.vannamei reared in low salinity waters.  Potassium: Compared with the other essential ions, potassium is a minor constituent in brackish and freshwater (Horne, 1969), but it plays important role in normal growth, survival, and osmoregulatory function of crustaceans (Mantel and Farmer, 1983). When reared in potassium deficient seawater, L.vannamei displayed anorexia, low activity, poor growth and even death (Zhu et al., 2004).  Calcium: the calcium requirement may be totally or partially met though absorption of calcium from the water (Deshimaru and Yone, 1978). The regulatory mechanism for calcium is obviously presented with an added challenge during the molt cycle of crustaceans, when there are large fluxes of calcium. Among various species, the concentration of total calcium consistently shows an increase during the period prior to the molt (Greenaway, 1985). Table 2: Ionic composition of seawater and freshwater Ingredient Concentration (mg/L) in freshwater Concentration (mg/L) in sea water Magnesium (Mg2+) 4 1,294 Calcium (Ca2+) 15 412 Potassium (K+) 2 399 Phosphorus (P) 20 35 (Source: Nicol, 1960; Burton, 1976; Liss, 1976) 2.2 Osmoregulation of shrimp Osmoregulation is an essential physiological process for the majority of aquatic crustaceans since it enables them to cope with the changes or discrepancies between the ion concentrations within their bodies and the aquatic environments they inhabit. The degree of the osmoregulatory response is largely salinity dependent, the actual strength is highly species-specific (Romano and Zeng, 2012). Huong and Wilder (2008) reported hemolymph osmolality of the shrimp (Litopenaeus vannamei) exposed to salinities of 0.5‰ or 1‰ decreasing rapidly from 800 mOsm to 540 mOsm after 6 hours. Levels also dropped dramatically from 800 mOsm to 560 mOsm in shrimp exposed to 3‰ after 6 hours and 1 day. Hemolymph osmolality of the white shrimps changed after exposure to low salinities, showing hyperosmoregulatory behavior in low salinities. The white shrimp (Litopenaeus vannamei) can not survive in low salinities (<1‰) because it loses the capacity to osmoregulate. 7 2.3 Effect of low salinity on the growth and survival rates of white shrimp (L.vannamei) The ability of L.vannamei to tolerate a wide range of salinities (0.5-40 ppt) has made it a popular species for low salinity culture (McGraw et al., 2002; Samocha et al., 1998; 2002). The high tolerance of L.vannamei to low salinity and the year-round availability of healthy postlarvae make this species an excellent candidate for inland farming. Therefore, recently, farmers have been focusing effort on culturing L.vannamei in low salinity environments. In lower salinity culture, there is an osmotic pressure between the shrimp body and the surrounding water, resulting in automatic water uptake mainly through gills and intestine. With lower salinity the shrimp face more difficulties to uptake minerals from the water. As nutrient intake directly and indirectly influences shrimp’s tolerance of stress, the supplementation of selected minerals and lipids above the levels typically used in marine shrimp feeds, beside supplementation in water directly. There is evidence from short-term exposures in culture tanks that both potassium and magnesium additions to well water will enhance survival and growth of postlarvae (Davis et al. 2005; Roy et al. 2007a). Roy et al. (2007a) reported an increase in shrimp growth when potassium levels were raised in low salinity waters. To date, several authors have established that when raising shrimp and other marine species in low salinity waters it is important to maintain sodium to potassium ratios (Na : K) at levels similar to seawater diluted to the same salinity (Fielder et al. 2001; Davis et al. 2004; Zhu et al. 2004; Roy et al. 2007a). 2.4 White shrimp (L. vannamei) production in the world: Litopenaeus vannamei was introduced into Asia experimentally from 1978-1979, but beginning in 1996, L. vannamei was introduced into Asia on a commercial scale. This started in Mainland China and Taiwan Province of China and subsequently spread to the Philippines, Indonesia, Viet Nam, Thailand, Malaysia and India (RAP, 2004). In 2008, 67% of the world production of cultured penaeid shrimp (3,399,105 tones) consisted of L. vannamei (2,259,183 tones). Such dominance was attributed to an 18fold increase of production in Asia, from 93,648 MT in 2001 to 1,823,531 MT in 2008, which accounts for 82% of the total world production of L. vannamei. China leads the world cultured L. vannamei production from 33% in 2001 to 47% in 2008 (1,062,765 MT), among which 51% (542,632 MT) were produced in inland freshwater pond (Liao and Chin, 2011). Thailand produced 299,000 tones, Vietnam 100,000 MT, Indonesia 103,874 MT of L.vanamei in 2005 (Kongkeo, 2007). 8 2.5 White shrimp (L. vannamei) production in Vietnam: Table 3: Production of white shrimp in North, Central and South of Viet Nam in 2009 Area Yield (MT) Percentage North 6,058 7.2% Central 63,554 75.4% South 14,708 17.4% Total 84,320 (MARD - Ministry of Agriculture and Rural Development) In Viet Nam, white shrimp cultured from 2000 but low production, reached 84,320 MT (MARD, 2009). However, in recent year, cultivation of white shrimp L. vannamei culture has been growing rapidly and become an important economic activity. In 2012, total exports of white shrimp were valued at 676.6 million USD (VASEP, 2013). In Mekong Delta, white shrimp reached 77,830 MT with 15,727 ha (VASEP, 2013). 9