World Aquaculture March 2019

42 MARCH 2019 • WORLD AQUACULTURE • WWW.WA S.ORG operations. The challenge was how to accomplish this. Under guidance of IMRAD staff, the initial focus was to use backyard milkfish hatcheries (Figs. 6 and 7). Concrete was used to construct larval rearing tanks, something that is cost-effective in Indonesia. Farmers used materials that were locally available, cost-effective and what they had the most experience with. Apart fromGondol and Negara on Bali, some milkfish hatcheries were also operating in Situbondo, Tanjung Kodok (in East Java) and in South Sulawesi (Patadjai 2001). The average harvest density in 1993 was 8 fry/L. Using a single 5,000 L rearing tank with a working volume of 4,000 L stocked with 80,000 eggs, an estimated 32,000 fry could be produced per three-week cycle. Using these production values, the estimated gross annual income in 1993 was 11 times the national average and about 50 times the income level of the rural poor. Using the values obtained, approximately 10,000 backyard milkfish hatcheries were needed to meet the national requirement for milkfish fry. By 2007 there were an estimated 8,000-10,000 backyard hatcheries throughout Indonesia, the number estimated to meet milkfish fry demands in 1993. Over the course of just 15 years apparently an explosion in milkfish fry production had taken place. Because of the increased production and subsequent drop in the price of milkfish fry, their increased availability also resulted in another industry, the production of milkfish for bait used to capture tuna, apparently well on its way prior to 1996 (FitzGerald 1996) (Figs. 8 and 9). By 2018 the number of backyard milkfish hatcheries in Indonesia had diminished to just over 2,000. Each backyard hatchery currently consists of at least four larval rearing tanks (10 m 3 each) with live feed production tanks. There are currently 14 complete hatcheries, each with more than 100 brooders, and larval rearing and live food production tanks. These hatcheries market milkfish eggs and fry. In addition, there are currently six partial hatcheries, each with more than 100 brooders, but no tanks are used for larval rearing as they market only fertilized eggs. Collectively the hatcheries produce approximately five billion milkfish fry per year, sufficient to provide the entire domestic market, with the excess exported to the Philippines, Taiwan, Malaysia, Thailand, Vietnam and Hong Kong. FromMilkfish to Groupers By 2018 some of the backyard and full-scale milkfish hatcheries included grouper production (Fig. 10). Currently grouper juveniles are produced and sold domestically and exported to Malaysia, Thailand, Vietnam and Hong Kong. The grouper species currently being produced in Indonesia are tiger grouper Epinephelus fuscoguttatus , coral grouper Plectropomus leopardus and humpback grouper Cromileptes altivelis . A reduction in the price for tiger grouper juveniles and increased demand by the Chinese market for another kind of grouper resulted in a collaboration between private farmers and the Aquaculture Institute in Situbondo, East Java. This collaboration resulted in commercial production of a hybrid grouper between a female tiger grouper and a male giant grouper ( E. lanceolatus ). This hybrid grouper currently has become the most popular grouper juvenile produced in Indonesia because of better growth and disease resistance. It is called cantang for the hybrid between macan (tiger grouper) and kentang (giant grouper). This is another example of how private and public sectors worked collaboratively, just as they did with the milkfish industry, and are now contributing to growth and diversification of the mariculture industry in Indonesia. In 2007, coral grouper juveniles produced in the Gondol area were stocked into net cages and fed a combination of trash fish and a commercial diet (Fig. 11), an example of how grouper culture was ABOVE, FIGURE 9. Harvest of milkfish to be used for bait for the tuna longline industry. RIGHT, FIGURE 10. Juveniles of P. leopardus produced in a backyard hatchery, Gondol, Bali, 2007