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Polyculture of black tiger shrimp Penaeus monodon, mud crab Scylla paramamosain, and red seaweed Gracilaria tenuistipitata, were applied in improved extensive ponds in the Vietnamese Mekong delta to evaluate production and financial efficiency. The trial consisted of two treatments: (1) non-feed supplement, in which shrimp consumed only natural food in the culture pond; and (2) feed supplement, in which shrimp received commercial feed (50% feeding rate). Treatments were in triplicate; ponds featured natural occurrence of red seaweed. Postlarvae of shrimp and crab were stocked at densities of 4 ind./m2 and 0.15 ind./m2, respectively, and culture for six months. Results showed that shrimp receiving feed supplement demonstrated much better (P < 0.05) growth and survival than those without feed supplementation. Shrimp yield was significantly higher (P > 0.05) in the feed supplement pond (348.9 kg/ha) than in the non-feed supplement pond (169.2 kg/ha). Crab production was similar between the two treatments (P > 0.05), varying from 88.1 to 92.4 kg/ha. Production cost (456.2 US$/ha) in the non-feed supplement pond was significantly lower than that in the feed supplement pond (944.8 US$/ha), but the former produced less profit (2,230.9 US$/ha) than the latter (4,169.2 US$/ha). Notably, the average benefit–cost ratio in the non-feed supplement group (4.84 times) was relatively higher compared to the feed supplement group (4.35 times). These findings suggest that polyculture of shrimp, crab, and seaweed in the improved extensive pond could be applied either non-feed supplement or feed supplement for shrimp, depending on the financial conditions of the farmers. [ABSTRACT FROM AUTHOR]

A pilot-scale experiment was conducted within an improved extensive pond to evaluate the efficiency of co-culturing black tiger shrimp (Penaeus monodon) and red seaweed (Gracilaria tenuistipitata) at different densities with partially reduced feed rations. Six treatments were established at random in triplicate with three stocking densities (2, 4, and 6 ind. m−2), and each density monocultured with either a 100% feed ration or co-cultured with red seaweed and a 50% feed ration. The culture system consisted of eighteen net enclosures (16 m2 each) installed in an improved extensive pond. After 4 months of culture, the growth rates of the shrimp decreased with increasing stocking density and shrimp yields at densities of 4 and 6 ind. m−2 were similar to each other (p > 0.05) and significantly higher (p < 0.05) than at a density of 2 ind. m−2. Notably, the growth rates, survival, and yield of shrimp in co-culture receiving a 50% feed ration were comparable to, and feed conversion ratio and feed cost were much lower than those in monoculture receiving a 100% feed ration at the same stocking density. The proximate composition of the shrimp meat in terms of moisture and protein levels was nearly equivalent in all treatments, while co-culture groups had lower lipid and higher ash content than monoculture groups. The results revealed that a co-culture of black tiger shrimp and red seaweed at a density of 4 ind. m−2 with a 50% feed ration maintained normal growth and increased shrimp yield while saving 40.45% of feed costs compared with monoculture. [ABSTRACT FROM AUTHOR]

Diseases in shrimp farms in the Mekong Delta of Vietnam cause significant crop losses and are therefore of great concern to producers. Once a pond becomes infected, it is difficult to prevent spread of the disease to nearby shrimp farming areas. Thus, predicting the occurrence of disease is an essential part of reducing the risk for shrimp farmers. In this study, we applied an integrated geographic information system and machine learning system to predict three serious diseases of shrimp, namely, acute hepatopancreatic necrosis, white spot syndrome disease, and Enterocytozoon hepatopenaei infection, based on data collected from shrimp farms in the Tra Vinh, Bac Lieu, Soc Trang, and Ca Mau provinces of Vietnam. We first constructed a map showing the distribution of these diseases using the locations of affected farms, and then we conducted spatial analysis to acquire the geographical features of the affected locations. This latter information was combined with environmental factors and clinical signs to form the set of independent variables affecting the outbreak of diseases. The neural network model outperformed the logistic regression, random forest, and gradient boosting methods in terms of predicting infection to estimate the probability of disease occurrence in farmed areas. Acute hepatopancreatic necrosis disease infected farms downstream of the Co Chien and Hau Rivers of Tra Vinh and west of Ca Mau. Enterocytozoon hepatopenaei infection is distributed in Soc Trang Province, while white spot syndrome virus has spread to the coastal districts of Soc Trang and Bac Lieu Provinces, where it is highly associated to water from a complex canal system. [ABSTRACT FROM AUTHOR]

The integration of seaweeds (extractive, low-footprint species) into aquaculture systems has been considered an alternative approach for the sustainable development of the shrimp industry, which aims to expand in an environmentally friendly way. Two consecutive experiments were conducted to evaluate the effects of integrating various densities of black tiger shrimp Penaeus monodon post-larvae (PL) and red seaweed Gracilaria tenuistipitata on water quality and shrimp performance in the nursery phase. The first experiment involved a 3 × 4 factorial design with three levels of shrimp density (1000; 2000 and 3000 PL m−3) and four levels of red seaweed density (0, 1.0, 1.5 and 2.0 kg m−3) randomly allocated in triplicate tanks for 30 days. Shrimp PL (with a mean weight of 0.012 ± 0.002 g and length of 1.12 ± 0.09 cm) and red seaweed were reared in 150 L tanks at a salinity of 15 g L−1. Significant synergistic effects between shrimp and seaweed densities were observed for the NO3− total nitrogen (TN) and PO43− contents, as well as for the survival (p < 0.05) and production of shrimp (p < 0.01). The integration of shrimp and red seaweed significantly decreased the concentrations of nitrogen and phosphorus in the rearing tanks and greatly enhanced the survival and growth rate of shrimp. In particular, increased stocking density resulted in poorer growth performance but enhanced production. Applying stocking densities of 1000 and 2000 PL m−3 obtained larger shrimp size, while a density of 3000 PL m−3 achieved the highest production output in the integrated system. In the second experiment, which followed the 30-day growth trial, shrimp quality was assessed via an immersion challenge test using pathogenic Vibrio parahaemolyticus (a concentration of 2 × 108 CFU mL−1) on the shrimp groups previously stocked at a density of 3000 PL m−3 and integrated with different quantities of seaweed. After 14 days of challenge, the cumulative mortality in the monoculture system averaged 75.6%, which was significantly higher (p < 0.05) than those in the integrated groups (17.8–31.1%). It is concluded that the integration of P. monodon shrimp and G. tenuistipitata improved tank water quality as well as shrimp survival and growth while also enhancing the antibacterial activity of shrimp against V. parahaemolyticus infection in the nursery phase. [ABSTRACT FROM AUTHOR]

Predicting the outbreak of disease is essential when managing shrimp farms. Acute hepatopancreatic necrosis disease (AHPND) caused by Vibrio parahaemolyticus is a serious disease in shrimp. It is essential that shrimp farmers on the east coast of the Mekong Delta detect the disease as early as possible, because the mortality rate can reach 100%. Here, we used machine learning to predict AHPND development based on data collected since 2010 from shrimp farms in Tra Vinh, Ben Tre, Bac Lieu, and Ca Mau provinces. We initially hypothesized that the dependent variable, AHPND, was affected by 31 independent variables, but ultimately used 15 key variables to train the models. Logistic regression, artificial neural network, decision tree, and K-nearest neighbor analyses were performed, and the accuracy of the predictions was evaluated using hold-out and cross-validation tests. Logistic regression, as the most stable algorithm, was thus used to predict AHPND outbreaks in shrimp farms. [ABSTRACT FROM AUTHOR]

The effects of integrating different densities of white leg shrimp Litopenaeus vannamei postlarvae (PL) and red seaweed Gracilaria tenuistipitata on water quality and shrimp performance were assessed in the nursery phase. A 3 × 4 factorial experiment with three levels of shrimp density (1000, 2000, and 3000 PL m−3) and four levels of red seaweed density (0, 1.0, 1.5, and 2.0 kg m−3) was randomly designed in triplicate. Shrimp PL12 (mean weight of 4.27 ± 0.28 mg) and red seaweed were stocked in 150-L tanks at a salinity of 15 g L−1 for 30 days. The results indicated that the integration of shrimp PL and red seaweed significantly reduced the nitrogen and phosphorus contents in the culture tanks and improved the survival and growth rate of shrimp, although not significantly. A significant interaction effect (p < 0.01) between shrimp and seaweed densities was only observed for shrimp production. Notably, higher stocking density resulted in lower growth performance but enhanced production. Applying stocking densities of 1000 and 2000 PL m−3 reared shrimp that were bigger in size, while a density of 3000 PL m−3 obtained the highest production output in the integrated system. Following the 30-day growth trial, shrimp quality was examined through a bacterial challenge test using pathogenic Vibrio parahaemolyticus on the shrimp groups previously reared at a density of 3000 PL m−3 and integrated with different amounts of seaweed. After 14 days of immersion challenge, the cumulative mortality in the control group was significantly higher than that of other groups. This result suggests that the presence of G. tenuistipitata improved the antibacterial activity of L. vannamei against V. parahaemolyticus during the nursery phase. [ABSTRACT FROM AUTHOR]

This study assessed the effects of the green seaweed Cladophora spp. as a protein source to substitute fishmeal protein in practical diets for postlarval tiger shrimp (Penaeus monodon). A control diet without containing seaweed meal was compared with five experimental diets in which fishmeal protein was replaced by increasing the levels of green seaweed protein (10, 20, 30, 40 and 50%) in the diets. All diets were formulated to be equivalent in crude protein (40%) and lipid (7%). Each dietary treatment was replicated in triplicate. After 45 days of the feeding trial, survival of the shrimp was not significantly influenced by the feeding treatments (p > 0.05). Growth rates of the shrimp fed with 10, 20, or 30% replacement levels of green seaweed protein in the diets were superior or similar to those fed with the control diet whereas shrimp fed with the diet containing 40 and 50% substitution levels showed significant reduction in growth (p < 0.05). The feed conversion ratio and protein efficiency ratio exhibited the similar trend as observed for growth performance. Moreover, shrimp fed with the control diet presented the lowest stress tolerance to formalin shock while the best performance was detected in the animals that received the 10 and 20% replacement diet. These results suggested that green seaweed Cladophora could replace up to 30% of fishmeal protein in the tiger shrimp postlarvae diet, and the optimal performance, including growth rate, feed efficiency, and stress resistance, appeared in shrimp fed with the diet of 10 to 20% substitution. [ABSTRACT FROM AUTHOR]