The study was conducted to determine the feasibility for growing-out of the spotted babylon juveniles (Babylonia areolata) to marketable sizes with the large-scale operation of 20.0 x 20.0 x 1.5 m earthen ponds at Petchaburi province, Thailand. The production and economic analysis for monoculture of spotted Babylon were compared with the polyculture with sea bass (Lates calcarifer). Each pond was stocked with juveniles of 0.3 g initial weight at a density of 200 snails [m.sup.-2]. This study provides good results in growth and production of spotted babylon in earthen ponds. The average growth rates in body weight were 0.67 and 0.51 g [mo.sup.-1] for snails held in the monoculture and polyculture with sea bass, respectively. At the end of the experiment, total yield of spotted babylon held in the monoculture and polyculture with sea bass was 10,520 and 10,450 kg [ha.sup.-1], respectively. Based on farm data, stocking data and harvest data used in this study, total cost per production cycle of the monoculture and polyculture with sea bass were $19,184 and $23,245, respectively. The cost of producing spotted babylon marketable sizes in this grow-out farm design was $5.69 per kg and $6.95 per kg for the monoculture and polyculture trials, respectively. At a farm gate price in 2003 of $9.00 per kg resulted in a net return of $11,124 and $14,691 for the monoculture and polyculture with sea bass, respectively. The present study indicated the technically feasible, and economically attractive for monoculture and polyculture of B. areolata to marketable sizes in earthen ponds.

Recently, there has been considerable interest in the commercial culture of spotted babylon, Babylonia areolata, in Thailand resulting from a growing demand and an expanding domestic market of seafood, and a catastrophic decline in natural spotted babylon populations in the Gulf of Thailand. From an aquaculture point of view, the spotted babylon had many biological attributes, production and market characteristics necessary for a profitable aquaculture venture and it was considered a promising new candidate of aquaculture species for the land-based aquaculture industry in Thailand (Chaitanawisuti & Kritsanapuntu 1999). At present, the successful culture of spotted babylon juveniles to marketable sizes was operated in large-scale production using the flow-through seawater system in concrete/canvas ponds. However, this culture technique had many considerations in disadvantages of the culture purposes. Basically, it needed the high investment of pond construction, buildings and facilities, large area for pond construction, and operational costs, but the production and low economic returns is not high enough for commercial operations (Chaitanawisuti et al. 2002a, 2002b). Because many marine shrimp ponds (Penaeus monodon) have been abandoned or rested because of diseases, poor management and environmental degradation for a long time in Thailand, this study was then focused on the potential and feasibility for a pilot growing-out of the spotted babylon juveniles to marketable sizes in earthen ponds. This study may provide an opportunity to develop a sustainable aquaculture system for growing out of spotted babylon juveniles to marketable sizes in earthen ponds and may result in the best use of many abandoned/rested shrimp ponds in coastal areas of Thailand. However, lack of economic data can be an important constraint to the successful development of spotted babylon aquaculture operations. A financial investment analysis which tied biological, production, cost and market price variables has been used to make decisions about culture methods, feasibility and potential for commercial operation of this enterprise. However, polyculture techniques have been used to increase production of fish and shellfish in culture ponds. Several marine shellfish species have been shown in polycultures, augmenting harvests through wider use of available food and space, whereas minimizing the negative effects of species--specific competitions and exometabolites. In addition, the polyculture of shellfish with fish presented some possibility that could benefit the local aquaculture operation (Hunt et al. 1995). A lack of economic data can be an important constraint to the successful development of spotted babylon aquaculture operations. A financial investment analysis which tied biological, production, cost and market price variables has been used to make decisions about culture methods, and feasibility and potential for commercial operation of this enterprise. Thereafter, the land-based aquaculture operation for growing-out of spotted babylon in earthen ponds was developed for commercial purposes in Thailand. The objective of this study is to present the growth, production and economic consideration for monoculture of juvenile B. areolata, and their polyculture with sea bass, L. calcarifer, using large-scale production of earthen ponds.