World Aquaculture March 2019

WWW.WA S.ORG • WORLD AQUACULTURE • MARCH 2019 63 ( C O N T I N U E D O N P A G E 6 4 ) After tank preparation, a mature male is stocked into the tank first. Soon after the male makes a bubble nest, a mature gravid female is stocked into the tank, which should be covered with a hard board to create humid conditions in the tank. Soon after stocking the female, both the male and female begin courtship behavior (e.g. chasing each other). During this period, the male bends around the abdomen of the female near the bubble nest, stimulating the deposition of about 500- 3,000 eggs in the bubble nest by the female, which are then fertilized by the male. The male also collects eggs and deposits them in the bubble nest. Soon after release of eggs, the female should be removed from the breeding tank. Inasmuch as this species is found in tropical regions, egg hatching requires no more than three days (24-36 hr). Within 3-5 days of hatching, hatchlings develop into free-swimming fry. Males guard eggs and larvae for 2-3 weeks in the wild, but larvae can be removed once they are free swimming. Larval Rearing Free-swimming larvae or fry are stocked into a rectangular aquaria or plastic tanks that are provided with diffused aeration and filtration of suitable size (Figs. 6 and 7). Larvae are fed with live food immediately after yolk-sac absorption. They are provided with sufficient quantity of infusoria or rotifers for one week, ensuring that minimum effort is required to search for food. After one week of rearing, larvae are fed Artemia nauplii, blood worms, sludge worms or mixed zooplankton until they reach stocking size. The 10-15 d old larvae may be stocked into other tanks to enable them to attain marketable size within 3-4 months. Periphyton can also be developed in the larval rearing tank through introduction of various types of artificial substrates such as plastic strips and aquatic plants that serve as feed for young larvae. In case live feed is not available, freeze-dried or refrigerated live food organisms can also be used. Feeding should be done 3-4 times per day for optimal growth and survival. Green water is also very useful for larval rearing of gourami. In this type of production system, specific varieties of phytoplankton (e.g. Spirulina, Chlorella) are cultured in a nutrient-rich media and used to feed larvae. Best management practices for breeding include: • Avoid aeration in breeding tanks because it will disturb nest formation. • Keep mature males separate in small containers because males are aggressive in the presence of a female. • Select healthy males for breeding because they will make larger bubble nests. • The size of the bubble nest is managed by placing small TABLE 4. Nutrient requirements of ornamental gouramis at different life stages. Nutrients Young stage Brood stock Sources Protein 40-45 30-40 Fish meal, Squid meal, shrimp meal, soyabean meal, mustard meal, groundnut meal, wheat/ maize meal etc. Lipid 4-6 6-8 Fish oil, vegetable oil (sunflower, soyabean oil etc.) Carbohydrate 40-45 40-45 Corn flour, rice bran, wheat bran Vitamin-Mineral 1-2 1-2 Synthetic forms FIGURE 6. Larval rearing in circular fiberglass tanks. FIGURE 7. Larval rearing in plastic tubs.