56 December 2011 the world, thirteen species of seahorses were cultured commercially, two species in research-only operations (Heather and Martin-Smith 2010). Notably, three species, the H. kuda, H. trimaculatus and H. comes, can change to a yellow color if these are cultured in tanks with a green bottom and background (Figure 1). In captivity, seahorse spawn 5 - 8 times per year , with brood size ranging from 200 – 1,700 embryo, depending on the species. Fry grow rapidly, reaching commercial size (7 - 10cm) in three to four months of culturing . Three species (H. kuda, H. comes and H. histrix) have been found to possess a closed life cycle, attaining a mature size after seven to ten months age. Seahorse in captivity feed well on frozen Mysis and Acetes. Survival rate from birth to adult is higher than 70 percent. In Vietnam, the production cost of live seahorse with length 6 – 8cm is US$1. The worldwide number of live seahorse traded from captivity ranges from 35,400 to 52,700 individuals, representing at least 33 declared species. In 2008, global production of cultured seahorse totaled 19, 336 individulas (Heather 2005,Heather and Martin-Smith 2010). In Viet Nam for 2010 alone, total culture production reached about 30,000 animals from three small hatcheries in Khanh Hoa province. Broodstock (Figure 2) are collected by divers or from F1 generation and are kept in tanks with 70cm of water depth. The feeding regime is the same as maintenance feeding, but some vitamins A, C and E are added to the feed to improve gonad quality and to strengthen fish larvae. In the spawning season, male and female mate for a few days in the morning, and then the female deposits her ripe eggs into the pouch of male. Embryo development takes place in this pouch within 10 - 20 days, depending on the temperature of water (Cai et al. 1984). With four pairs of male and female in captivity, about 1,500 juvenile seahorse are produced per month. Using this method, as we are doing in Vietnam, the development of seahorse aquaculture does not depend on broodstock from the wild. After giving birth, broodstock in spawning tanks (0. 5 m3 tanks, Figure 3) are removed to mating tanks for the next spawning. The fry are cultured at a density of 1 -2 /L, and the environmental conditions are maintained at 30 – 25 ppt salinity, 4 – 5ppm DO, pH 8.0 – 8. 3, NH3 at zero, and at a temperature range of 26 – 28o C. Fry are fed copepoda three times per day from birth to 40 days old. Copepoda are fed at density 3 – 5/mL/time. In addition, enriched Artemia nauplii (A1 DHA Selco, INVE) are fed to fry from 10 days onwards at the same density as copepoda. Some authors use only enriched Artemia for producing seahorse fry, however their survival rates are comparatively low (Payne and Rippingale 2000, Chang et al. 2001); whereas when feeding with Copepod and enriched Artemia, the survival reaches an average of more than 90percent. After 40 days, juvenile seahorse (Figure 4) are transferred to bigger tanks, 2 – 4/m3. The stocking density is Fig 3. Seahorse fry seahorse tank Fig 4. Seahorse fingerling H. comes Fig 5. Grow – out tanks (2 m3) (Continued from page 54)
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