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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]

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]

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]

The on-farm trials of rotational rice-prawn farming in a semi-deep water area in the Mekong Delta of Vietnam was carried out in six rice fields (0.7-1.0 ha) to evaluate the production and economic efficiency of using low and high cost teed on prawn culture in paddies at different densities. Two stocking densities of 4 and 5 PL/m² were investigated. Two treatments of feed types (pellets only or a combination of pellets, trash fish, and snail meat) were applied at stocking 4 PL/m². At the treatment of 5 PL/m², prawns were fed a combination of pellets, trash fish, and snail meat. Prawns were stocked in the mid-April and harvested in mid-November before the next dry season rice crop. Rice farming was started 3 to 5 days after prawn harvesting. By cull harvesting during the culture period, final mean weights of prawn ranged from 47.2 to 57.2 g/prawn and the male:female ratio at harvesting was 2.5:1.0. The prawn yield of treatment 5 PL/m² was highest (630 ± 22 kg/ha). Net profits in treatments using the combination of pellets, trash fish, and snail meat were 861 ± 193 US$/ha to 1,019 ± 25 US$/ha for the prawn crop and 1,393 ± 71 US$/ha to 1,576 ± 180 US$/ha for the whole system (prawn crop + dry rice crop) and significantly higher than in treatment using pellet only (P < 0.05). Prawns fed on pellets or a combination of pellets and snail meat both offer similar results in terms of production and economics. The dry rice crop offered high cost benefit ratio (2.29-2.33) with low operating cost (414-434 USD/ha) and it made a better use in sustainable rice fields through the rotational rice-prawn system. [ABSTRACT FROM AUTHOR]

Postlarvae (PL) of Macrobrachium rosenbergii (de Man 1879) were stocked at 1, 2, 3 and 4 PL m−2. Prawns were fed only pellets (P) and a combination of pellets and snail meat (PS) with three replications in 100 m2 plots in the rotational prawn–rice system. Water levels were 0.3–0.6 m in rice growing areas. The water temperatures at noon in the hot months were higher than the suitable range for prawns. The final mean weights of prawns in treatments 1, 2 and 3 PL m−2 were significantly higher than in treatment 4 PL m−2 ( P<0.05). The yields from different density treatments ranged from 194±82 to 373±32 kg ha−1 and increased significantly with the increases in prawn densities ( P<0.05). There was no significant difference between the two types of feed on production parameters ( P>0.05). The total cost significantly increased at higher densities ( P<0.05), but it was not different between feed types ( P>0.05). Net profit and cost benefit ratio of treatment PS were significantly higher than in treatment P. In the present study, treatment 3 PL m−2 and treatment PS offered the optimal results. [ABSTRACT FROM AUTHOR]

Post larvae of Macrobrachium rosenbergii (de Man 1879) were stocked at 2, 4, and 6 postlarvae (PL)/m2 into rice fields under two culture systems, the integrated and the rotational prawn-rice system. Prawn was fed pellet feed twice daily. The growth of Macrobrachium rosenbergii decreased at higher stocking densities. Prawns in the rotational system grew faster than those in integrated system. The yields ranged from 286 ± 32 to 527 ± 51, 412 ± 17, to 538 ± 37 kg/ha in the integrated and the rotational prawn-rice system, respectively. The yield at density of 2 PL/m2 was significantly lowest (P < 0.05) and was highest in the treatment with 6 PL/m2. However, at higher density, the investment cost significantly increased (P < 0.05), while profit significantly decreased (P < 0.05). At a density of 2 PL/m2, cost benefit ratio and profit was the highest (P < 0.05). The integrated rice-prawn system gives lower profits than the rotational system. [ABSTRACT FROM PUBLISHER]