34 MARCH 2015 • WORLD AQUACULTURE • WWW.WAS.ORG Current Status of Shrimp Farming Technology Integrated mangroveshrimp farming systems and improved extensive farming systems. Two traditional and typical shrimp farming systems with rather similar farming methods are the integrated mangroveshrimp farming system (Fig. 5a) and the improved extensive farming system (Fig. 5b). These were developed and have existed mainly in the Mekong Delta since the 1980s until the present. Integrated mangrove-shrimp farming systems are located in the buffer zone, behind the full protection zone of the coastline. In contrast, the improved extensive shrimp farming system is practiced in the economic zone, behind the coastal buffer zone. Major characteristics of these systems are shown in Table 3. Both systems are characterized by a rather large farm area (3-10 ha), consisting of a platform (60-80 percent), ditch (20-40 percent) and surrounding dikes. For the integrated mangroveshrimp farming systems, mostly Rhizophora mangrove trees are planted at about 50-70 percent of the platform area. For the improvedextensive shrimp farms, aquatic plants (Scirpus littoralis, Typha sp.), seaweeds (Enteromorpha, Chaetomorpha, Cladophora, Gracilaria) or mangrove trees are planted or allowed to develop naturally on the platform. These plants are good for the environment and create excellent habitat for shrimp, fish and especially mud crabs. In these systems, wild shrimp, fish and crabs are taken into farms through tidal water exchange during periods around the full moon and new moon. In addition, hatchery-reared black tiger shrimp postlarvae companies using intensive farming systems (Fig. 4a). Hatchery capacity of larval rearing tanks ranges from 48 to 2800 m3 for black tiger shrimp and 60 to 6500 m3 for Pacific white shrimp. Black tiger shrimp broodstock are mostly large individuals (250-350 g) caught from the sea. Pacific white shrimp broodstock were mostly imported from other countries (Hawaii, USA, Thailand and Singapore). Recently, trials on domestication of Pacific white shrimp broodstock have been practiced by different research institutes and companies 2, 3 (Tao 2013). For larval rearing, two major techniques have been applied: open clearwater systems and recirculating systems. Open clearwater systems (Fig. 4b) are applied mainly in large hatcheries near the coast with an abundance of seawater. Recirculating systems, developed by Can Tho University, are applied mainly in hatcheries in Can Tho City, where brine from salt pans is used for production. Larvae for rearing can be from broodstock cultured at hatcheries or bought from other hatcheries, especially Pacific white shrimp larvae from hatcheries in the central provinces. The stocking density of black tiger shrimp larvae is 100-250 nauplii/L and the survival rate to postlarvae is 50-70 percent. For Pacific white shrimp, the stocking density is 150300 nauplii/L and survival is 40-60 percent. Diatoms are used for Pacific white shrimp larval culture (Fig. 4c). Because most of the Pacific white shrimp hatcheries are large scale (Fig. 4d), average annual production is 47-1,780 million postlarvae/hatchery, which is much greater than that of small-scale black tiger shrimp hatcheries (39-172 million postlarvae/hatchery). A. B. C. D. FIGURE 4. Shrimp hatcheries and seed production in Vietnam: (A) large-scale hatchery, (B) larval rearing tanks with open, clearwater system, (C) modern system for diatom algae culture, (D) white leg shrimp hatchery. FIGURE 5. Shrimp farming systems in Vietnam: (A) integrated mangrove-shrimp farming system, (B) improved extensive shrimp farming system, (C) alternative rice-shrimp farming system, (D) intensive shrimp farming system. A. B. C. D.
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