34 JUNE 2023 • WORLD AQUACULTURE • WWW.WAS.ORG of outdoor pond production of Artemia can now be recognized in Thailand. Artemia Production from Hatchery Wastewater Treatment In Thailand, hatchery wastewater needs to be treated before release to natural waters. Biodegradation and natural waste treatment requires 70 percent additional land than the original hatchery complex. In marine shrimp hatcheries, the bio-extraction components include mangrove trees and phytoplankton to trap the waste nutrients and suspended particles. The black tiger shrimp farm of Mr. Banchong Nissagavanich in Chachoengsao Province, nearly 60 km east of Bangkok, developed an original idea. On his farm, Artemia is produced within the wastewater treatment facilities as an additional high-value crop. This Artemia farm was already described in a 2005 article on “Recycling water and making money” (Kongkeo and Wilkinson 2005). Most of the wastewater treatment area allows evaporation and the last line of reservoir ponds usually has a higher salinity and less suspended solids to allow Artemia production. With one can of Artemia cysts added to two ponds in the 1990s, the farm has maintained continuous production of Artemia for the last 30 years without adding new cysts. The entire hatchery complex refreshes water once a year and keeps the brine water stored before the annual water exchange. Due to high salinity, until now there has been no record of disease in feeding this live biomass to Penaeus monodon and Macrobrachium broodstock as well as postlarvae. The key is to be able to maintain salinity between 70-90 g/L always, even during the rainy season. Two ponds are in operation on a year-round basis. The ponds have a surface area of about 6500 m² and a depth of 2 m, so as to be able to drain, on the four sides of the ponds, the freshwater runoff from heavy rainfall during the rainy season. With a salinity of 110 g/L at the start of the rainy season, it falls to only 70-80 g/L at the end of the rainy season. In addition to maintaining high salinity, understanding the maximum daily harvest level is also important to be able to maintain consistent daily harvest. Optimum daily harvest allows the existing stock to grow within a 24-hr period to replenish the Artemia population. Unlike fish, food for Artemia is not expensive. Ami-ami, as well as different wastes of plant and fruit processing, cow dung and even kitchen waste are used as organic fertilizers and added daily (Fig. 3). Every other day the pond bottom is raked with a heavy chain dragged by boat over the pond bottom (Fig. 4). Harvesting of the Artemia biomass that accumulates at the water surface in the early morning hours when low dissolved oxygen levels prevail is pushed into a harvesting net by a paddlewheel (Fig. 5). Thus, the Artemia production in the Banchong farm is turning the agro-industrial and green waste into high-protein biomass. Harvest yields are 100-120 kg wet weight Artemia biomass per pond per day or approximately 4.5 t/ha per mo. From this farm, 60 kg live weight of Artemia are sold every day for US$1.75/kg to crab and marine fish hatcheries as live food. The cost of production is less than US$0.50/kg. As a result, this farm makes an annual profit of US$27,000/yr by supplying 21.6 t of live Artemia from only 0.6 ha of dedicated pond area. Artemia Production from an External Waste Stream Mr. Tanan made an example of Artemia production as his major farming crop and livelihood. Only 20 percent of the total farm area has been allocated for salinity concentration by evaporation and the remaining 4-ha area is entirely used for Artemia production. This farm is located in the salt production areas of Phetchaburi, approximately 140 km from Bangkok city center. Here the only nutrient input is chicken manure and cow dung. This is a very low cost method but nutrient release is slow. As a result, daily harvest is FIGURE 4. A heavy chain is dragged across the Artemia pond bottom every other day. FIGURE 5. Harvesting an Artemia pond. The slowly turning paddlewheel and bamboo guides direct Artemia into the shallow set-net fixed in position behind, where it can be easily removed (Photos: NACA). FIGURE 6. Net cages used to collect Artemia at Tanan farm near Phetchaburi, Thailand.