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Growth, production and economic evaluation of earthen ponds for monoculture and polyculture of juveniles spotted babylon (Babylonia areolata) to marketable sizes using large-scale operation.

ABSTRACT 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.

KEY WORDS: Babylonia areolata, Lares calcarifer, monoculture, polyculture, earthen ponds, production, economic analysis

INTRODUCTION

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.

METHODS

Pond Design and Construction

This study was conducted at the Research and Development Unit for Aquaculture of the spotted babylon, Aquatic Resources Research Institute, Chulalongkorn University, Petchaburi province, Thailand, during 2003 to 2004. A total farm area of 0.8 ha was comprised of 0.32 ha grow-out earthen ponds, 0.4 ha seawater reservoir and 0.08 ha accommodation and office. Eight 20.0 x 20.0 m earthen ponds and 1.5 m in depth were used for the polyculture trials. Ponds were arranged in a 4 x 4 array with common walls to reduce construction costs and pond wall was 1.5 m in height, 3.0 m in width at the base and 2.5 m in width at the top. Ponds bottom was covered with coarse sand of approximately 10-15 cm in thickness. Each grow-out pond was fenced by plastic net of 15.0 mm mesh size and 1.2 m in width, supported with bamboo frame for strengthening. The plastic net must be buried under sand about 6 cm in depth to limit movement of snails along pond bottom and pond wall, and ease for harvesting. Prior to the start of the grow-out, all ponds were dried for 2 wk, and filled with ambient, unfiltered natural seawater from a nearby canal to a depth of 70 cm. Water level in the ponds was maintained at 70 cm by adding seawater to replace water loss caused by seepage and evaporation. The grow-out ponds are supplied with ambient unfiltered, natural seawater from seawater intake system. The seawater system was powered by one 5.5-hp engine equipped with water pump of 12.5 cm in diameter of outlet pipe. The seawater intake consisted of a 12.5 cm in diameter PVC pipe manifold horizontally into the sea. Seawater is delivered to each pond through main unlined canal of 80-cm width and 30-cm depth, and 15.0-cm diameter PVC distribution pipes (inlet). The drainage pipe of 12.5 cm in diameter PVC pipe was used as an outlet. Two air blowers (2 Hp) were used to supply high volume of air for all grow-out ponds. PVC pipes of 2.54 cm in diameter were connected to the outlet of the air blower and extended to the pond dike of each pond. Four polyethylene pipes of 18 m long and 1.6 cm in diameter was connected to the PVC pipe and extended to the bottom of each pond. On the PE pipe, there were 10 holes of 1.5 mm in diameter, and the distance between adjacent holes was 2 m. The PE pipes were sustained at 10 cm off the pond bottom using bamboo sticks. An aerator was operating daily for 16-20 h except during feeding and resting of blower.

Monoculture and Polyculture Trials

Spotted babylon and sea bass juveniles were purchased from private hatchery. Individuals from the same cohort were sorted by size to minimize differences in shell length (maximum anterior-posterior distance) and prevent possible growth retardation of small babylon when cultured with larger individuals. The spotted babylon juveniles had an average shell length and body weight of 1.0 cm and 0.3 g, respectively, and 12.7 cm and 37.2 g for those of sea bass, respectively. Two treatments of monoculture and polyculture were designed as following:

Treatment 1: Monoculture of Spotted Babylon

Initial stocking density of spotted babylon juveniles was 200 individuals [m.sup.-2] (80,000 snails per pond).

Treatment 2: Polyculture of Spotted Babylon with Sea Bass

Initial stocking density of spotted Babylon and sea bass juveniles were 200 individuals [m.sup.-2] (80,000 snails per pond), and 5 fish [m.sup.-2] (2,000 fish per pond), respectively.

Grow-out Operation

The feeding schedule was as follows: sea bass were fed to satiation with fresh trash fish twice daily in morning (09:00 h) and evening (17:00 h). Spotted babylon were fed with fresh trash fish at 15% to 20% of body weight once daily in morning (09:00 h) this was done after stopping feeding of the sea bass. Feeding was monitored daily by means of baited traps. Food amounts were adjusted every 30 d after body weight measurement. Fifty percent of seawater was exchanged at 15 d interval and seawater was sampled before water exchange at 25 cm above pond bottom for analyses of seawater temperature, salinity, pH, alkalinity, nitrite-nitrogen and ammonia-nitrogen following standard methods as described by APHA et al., 1985. Dissolved oxygen was measured daily. No chemical or antibiotic agent was used throughout the entire experimental periods. Grading by size was not carried out in any pond throughout the growing -out period. For growth estimation, 50 baited traps were used to sample the spotted babylon in each pond at 30 d interval for measurement of body weight individually and counting the number of snails per kg. The spotted babylon juveniles were cultured until they reached the marketable size of 120-150 snails per [kg.sup.-1].

Economic Evaluation

The components of financial analysis were categorized according to initial investment, annual ownership costs and annual operating costs as follows:

Initial investment requirements for farm construction on monoculture of juvenile spotted babylon and polyculture with sea bass to marketable sizes in earthen ponds were evaluated. The investment requirements included land, construction of eight 20.0 x 20.0 x 1.5 m grow-out earthen ponds, one 0.4 ha seawater reservoir, two seawater pumps and housing, two blowers and housing, four 3.0 x 5.0 x 0.7 m canvas nursery tanks and housing, accommodation for labor and office and operating equipment and facilities.

Ownership costs per production cycle consisted of land, depreciation and interest on investment. These costs are fixed and incurred in the short run regardless of whether the facilities are in operation. Annual depreciation was estimated by the straight-line method, based on the expected useful life of each item of equipment. Assets are assumed to have no residual value for all items constituting facilities at the end of their useful life. Eight 20.0 x 20.0 x 1.5 m grow-out earthen ponds and one 0.4 ha seawater reservoir were assumed to have useful life of 5 and 2 y, respectively. Housing and the blowers and seawater pumps were assigned a useful life of 2 y. The life expectancies of equipment ranged from 1-2 y. Interest rates for capital cost were based on 2003 bank loan rates (3.5% per year) for this type of business enterprise.

Operating costs per production cycle are incurred upon actual operation of the grow-out unit and include repairs and maintenance, labor, feed, utilities and interest on operating capital. Costs for purchasing and transportation of spotted babylon and sea bass juveniles are $0.02 and 0.11 per juvenile, respectively. Spotted babylon and sea bass are fed fresh meat of trash fish at a cost of $0.13 per 0.18/kg and feed conversion ratio was 2.2. The repairs and maintenance is estimated on the actual expenses for housing, earthen ponds, reservoirs, and operating equipment costs. Electricity is used for operating the various pumps and lighting units in the farm. The average charge was $0.03 per kilowatt hour. Labor requirements were based on the particular needs for production cycle of the proposed farm. Two operators (full-time) were assigned for operation of the farm; the cost of one operator was $125.0 per month. Operating equipment (fuel, storage containers, farm equipment, etc.), chemicals and lime was estimated based on actual use of each item. Land is actual lease from private sector at a rate of $625 per ha per year. Interest charges for operating capital are based on 2003 bank loan rates (3.5% per year) for this type of business.

Return Analysis

Net return and return on investment for grow-out production were computed at the selling price of spotted babylon market sizes at farm gate in 2003 ranging from $8.8-9.3/kg. Gross return was computed from total yield multiplied by selling price. Net return was calculated from the gross return minus to the total amount cost per production cycle. (Rubino 1992, Fuller et al. 1992).

RESULTS

Growth and Production

Growth expressed as body weight and number of snail per kilogram of juvenile B. areolata for monoculture and polyculture with sea bass over a period of 7 mo was shown in Figure 1 and Figure 2. Growth of spotted babylon was not significantly higher in monoculture, compared with growth in polyculture with sea bass (P < 0.05). 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. Mean ([+ or -] SE) final body weights of spotted babylon held in the monoculture and polyculture with sea bass was 5.22 [+ or -] 0.63 g, and 4.10 [+ or -] 0.57 g, respectively. Mean ([+ or -] SE) final shell lengths of snails held in the monoculture and polyculture with sea bass was 3.2 [+ or -] 0.35 cm, and 3.6 [+ or -] 0.75 cm, respectively. The snails can reach the sizes of 205 [+ or -] 17.55 and 214 [+ or -] 43.90 individuals [kg.sup.-1] for the monoculture, polyculture with sea bass, respectively. Feed conversion ratio (FCR) was 2.69 and 2.71 for snails held in the monoculture and polyculture with sea bass, respectively. Final survival of snails held in the monoculture was 84.94%, and 84.30% for those held in polyculture with sea bass, respectively. At the end of the experiment, the average total yield of spotted babylon in monoculture and polyculture with sea bass were 10,525 and 10,450 kg [ha.sup.-1], respectively. Size distribution of the spotted babylon in monoculture was consisted of 2 main size classes of 100-250 and <250 snails/kg with 90.81% and 9.19%, respectively. For Polyculture with sea bass, the snails consisted of 2 main size classes of 100-250 and <250 snails [kg.sup.-1] with 87.57% and 12.43%, respectively. For sea bass, the average final weight, final survival, FCR and total production were 300-1,200 g, 46.0%, 4.47 and 12,250 kg [ha.sup.-l], respectively.

[FIGURE 1 OMITTED]

Economic Evaluation

Farm data (total farm area, pond sizes and total pond area), stocking data (average initial weight, stocking density) and harvest data (duration of grow-out, average weight at harvest, final survival, feed conversion ratio and yield) are based on the actual data of pilot farm. Parameters used for the economic analysis for monoculture and polyculture of spotted Babylon with sea bass in a total farm area of 0.8 ha were summarized in Tables 1, 2, 3, 4, 5. Total investment requirement for construction of a total farm area of 0.8 ha was estimated to be $4,837 for the monoculture and polyculture trials. Construction of grow-out ponds and seawater reservoirs was the largest cost component of the farm (35.14% of the total investment cost), followed by building of canvas nursery ponds, land, seawater pumps and blowers representing 12.92%, 10.34%, 10.34% and 10.34% of the total investment cost, respectively (Table 2). Ownership cost per production cycle was estimated to be $2,241 for the monoculture and polyculture trials. The major ownership cost items were depreciation, land and interest on investment accounting 76.22%, 22.31% and 1.47% of total ownership cost, respectively (Table 3). Operating costs per production cycle was estimated to be $16,943 and $21,004 for the monoculture and polyculture trials, respectively (Table 4). Total cost per production cycle for the monoculture of spotted babylon in a total farm area of 0.8 ha was $19,184 and $23,245 for the monoculture and polyculture trials, respectively (Table 5). 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. The enterprise budgets based on the price of spotted babylon at farm gate in 2003 of $9.00 per kg resulted in net return of $11,124 and $14,691 for the monoculture and polyculture trials, respectively (Table 6).

DISCUSSION

In this study, the average monthly growth rate, FCR and final survival of spotted babylon for monoculture in earthen pond were 0.67 g [mo.sup.-1], 2.69, and 84.94%, respectively, and the average monthly growth rate, FCR and final survival of spotted babylon were 0.51 g [mo.sup.-1], 2.71, and 84.30% respectively for polyculture with sea bass. The snails can reach a marketable size with an average body weight of 9-10 g in a 7-mo period of culture. By contrast, Chaitanawisuti and Kritsanapuntu (1999) reported that average monthly growth rates of spotted babylon in flow the through culture system in concrete/canvas tanks was 1.4 g [mo.sup.-1]. FCR and final survival were 1.6% and 95.8%, respectively. Chaitanawisuti et al. (2001) reported polyculture of B. areolata and L. calcarifer in 3.0 x 4.5 x 0.5 m concrete ponds supplied with flow-through seawater system that the average growth, survival, FCR and total production were 1.17 g [mo.sup.-1], 96.0%, 1.34 and 29.0 kg, respectively. Growth of spotted babylon in earthen ponds was lower than those in concrete/canvas tank. The most concerned major issues for slow growth of spotted babylon in earthen ponds is the soil sanitization caused by pond seepage, salinity increases caused by water evaporation, salinity decrease caused by heavy rain falls, fast deterioration of total alkalinity, appropriate feeding strategy and invasions of snails (Cerithium sp.) as follows: (1) excessive food caused the degradation of water quality and decay of pond bottom; (2) food competition from various predators such as the tiger prawn naturally occur in earthen ponds (Peneaus monodon), swimming crabs (Portunus pelagicus), mud crab (Scylla sp), carp (Orechormis mossambica); (3) deterioration of water quality, particularly total alkalinity which, caused slower feeding of spotted Babylon; (4) salinity decrease during rainy season, which caused slower feeding and obvious slow growth and (5) mineral competition from a large number of snails (Cerithium sp.) that competed for minerals in the seawater, particularly calcium for shell formation, which resulted in shell abnormality and slow growth. In this study, production and economic analysis was performed for monoculture of juvenile B. areolata to marketable sizes using a large-scale production of earthen ponds in Thailand. The analysis was based on actual cost and production data from a pilot commercial-scale farm. A total farm area of 0.8 ha was comprised of 0.3 ha grow-out earthen ponds, 0.4 ha seawater reservoir and 0.08 ha accommodation and office.

The enterprise budgets of monoculture based on the price of spotted babylon at farm gate in 2003 of $9.00/kg, net return of the monoculture and polyculture were $11,124 and $14,691, respectively. This study presented a positive net return and a payback period of less than five years are often used as business investment criteria. In Thailand, living spotted babylon fetched the selling prices ranging from $11.25-15.00/kg at seafood restaurants and $8.75-9.25 per kg at a farm outlets. The basic consumption in this study (juvenile price of $0.02 per juvenile, production feed price of $0.2 per kg, stocking density of 200 snails [m.sup.-2], and selling price of $9.0 per kg) indicated that the proposed eight 20.0 x 20.0 x 1.5 m grow-out earthen ponds operation is economically feasible under these conditions. The feasibility of producing spotted babylon marketable sizes in pilot commercial grow-out earthen pond operation should be continued to be examined. Although returns are small, production with 80% survival and selling price of $9.0 per kg is economically feasible under the assumptions used. The results showed that total yield of monoculture (10,520 kg/ha) and poly culture with sea bass (10,450 kg/ha) was gradually different. For cost and returns analysis, total cost per production cycle of polyculture with sea bass ($23,245) was 17.47% higher than that of monoculture ($19,184) because of increasing costs of sea bass juveniles and feed, and the net return per production cycle of polyculture with sea bass ($14,691) was 24.28% higher than the monoculture ($11,124). Results of this work showed that juvenile spotted Babylon could be successfully grown to marketable size in earthen ponds for monoculture and polyculture systems.

This study has basically demonstrated that it is possible to culture the spotted Babylon in earthen ponds such as the abandoned/rested shrimp ponds by stocking acclimated spotted babylon juveniles to marketable sizes. Thus, monoculture and polyculture of spotted babylon is environmentally friendly and economically attractive with appropriate abandoned/rested shrimp farms, resulting in effective reuse of abandoned shrimp ponds, better economic returns and less environmental pollution. Furthermore, the polyculture of spotted babylon with sea bass or milkfish at relatively low stocking density may provide an opportunity to develop a sustainable aquaculture system to best use many abandoned/rested shrimp ponds in various coastal areas of Thailand. The results of this study provide preliminary evidence for the biological feasibility of culturing the spotted Babylon, B. areolata, in earthen ponds for monoculture and polyculture. However, application of these results to commercial levels of production should be preceded by careful examination of other parameters that might be important, such as deterioration of water quality at high stocking densities. Further study should concentrate on pond design, management of seawater and pond bottom quality, feeding strategy and competition for food and habitat caused by natural occurrence of organisms, for the success of commercial grow-out operation of spotted babylon in earthen ponds.

ACKNOWLEDGMENTS

The authors thank the National Research Council of Thailand (NRCT), who provided funding for this research in fiscal year 2003 to 2004. The authors also express sincere thanks to Professor Dr. Yutaka Natsukari, Faculty of Fisheries, Nagasaki University, for his supervisors who were involved in the research and revision of this manuscript.

LITERATURE CITED

APHA, AWWA, & WPCF. 1985. Standard methods for the examination of water and wastewater, 16th Edition. American Public Health Association, American Water Works Association and Water Pollution Control Federation, Washington, DC. 1268 pp.

Chaitanawisuti, N. & A. Kritsanapuntu. 1999. Growth and production of hatchery-reared juvenile spotted babylon Babylonia areolata Link, 1807 cultured to marketable sizes in intensive flow-through and semi-closed recirculating water system. Aquaculture Res. 31:415-419.

Chaitanawisuti, N., A. Kritsanapuntu & y. Natsukari. 2001. Growth trials for polyculture of hatchery-reared juvenile spotted babylon, Babylonia areolata Link 1807, in flow-through seawater system. Aquaculture Res. 32:247-250.

Chaitanawisuti, N., S. Kritsanapuntu & y. Natsukari. 2002a. Economic analysis of a pilot commercial production for spotted babylon Babylonia areolata Link, 1807 marketable sizes using a flow-through culture system in Thailand. Aquaculture Res. 33:1-8.

Chaitanawisuti, N., A. Kritsanapuntu & y. Natsukari. 2002b. Effects of different types of substrate on the growth and survival of juvenile spotted babylon Babylonia areolata Link, 1807 reared in a flow-through culture system. Asian Fish. Sci. 14:279-284.

Hunt, J. W., M. S. Foster, J.W. Nybakken, R.J. Larson & E.F. Ebert. 1995. Interactive effects of polyculture, feeding rate, and stocking density on growth of juvenile shellfish. J. Shellfish Res. 14:191-197.

Fuller, M.J., R.A. Kelly & A.P. Smith. 1992. Economic analysis of commercial production of freshwater prawn Macrobrachium rosenbergii postlarvae using a recirculating clearwater culture system. J. Shellfish Res. 11:75-80.

Rubino, M. C. 1992. Economic of red claw Cherex quadricarinatus aquaculture. J. Shellfish Res. 11:157-162.

S. KRITSANAPUNTU, (1) N. CHAITANAWISUTI, (2) * W. SANTHAWEESUK (2) AND Y. NATSUKARI (3)

(1) Faculty of Technology and Management, Prince of Songkla University, Suratani, Thailand; (2) Aquatic Resources Research institute, Chulalongkorn University, Bangkok, Thailand 10330; (3) Faculty of Fisheries, Nagasaki University, 1-14 Bunkyo-Machi, Nagasaki, 852 Japan

* Corresponding author. E-mail: nilnajcl@hotmail.com
TABLE 1.
Parameters used for the economic analysis for the monoculture and
polyculture trials of spotted babylon in a total farm area of 0.8 ha
of earthen ponds.

 Monoculture Polyculture

Parameters Amount ($) Amount ($)

A. Farm data
 Total farm area (ha) 0.8 0.8
 Pond size (ha) 0.04 0.04
 Total pond area (ha) 0.3 0.3
 Total area of seawater
 reservoirs (ha) 0.4 0.4
B. Stocking data
 Average initial weight of spotted
 babylon (g) 0.3 0.3
 Average initial weight of sea
 bass (g) 2.3
 Stocking density of spotted
 babylon (no. [m.sup.-2]) 200 200
 Stocking density of sea bass
 (no. [m.sup.-2]) 5
C. Harvest data (Spotted Babylon)
 Duration of grow-out (mo) 7 7
 Average number of crops per
 year per pond 1.4 1.4
 Average final weight (g) 5.22 4.10
 Average final survival (%) 84.94 84.30
 Feed conversion ratio (FCR) 2.69 2.71
 Yield per production cycle
 (kg/ha) 10,520 10,450
 Selling price at farm gate ($/kg) 8.75-9.25 8.75-9.25
D. Harvest data (Sea bass)
 Duration of grow-out (mo) 6
 Average number of crops per
 year per pond 2
 Average final weight (g) 300-1,200
 Average final survival (%) 46.00
 Feed conversion ratio (FCR) 4.47
 Yield per production cycle
 (kg/ha) 12,250
 Selling price at farm gate ($/kg) 1.89-2.25

TABLE 2.
Estimated investments requirements for the monoculture and
polyculture trials of spotted babylon in a total farm area of 0.8 ha
of earthen ponds.

Items Amount ($) %

Land renting 500 10.34
Construction of eight 20.0 x 20.0 x 1.5 m
 grow-out earthen ponds and one 0.4 ha
 seawater reservoirs 1,700 35.14
Construction of accommodation and storage
 house 250 5.17
Construction of four 3.0 x 5.0 x 0.7 m
 canvass nursery ponds and housing 625 12.92
Water pumps and housing 500 10.34
Blowers and housing 500 10.34
Traps for sampling and harvesting 100 2.06
Operating equipment (pvc pipes, lighting,
 salinometer, thermometer, ect) 162 3.35
Miscellaneous 500 10.34
Total investment 4,837 100

TABLE 3.
Estimated ownership costs per production cycle for the monoculture
and polyculture trials of spotted babylon in a total farm area of 0.8
ha of earthen ponds.

Items Amount ($) %

Land 500 22.31
Depreciation
 Construction of grow-out earthen ponds
 and seawater reservoirs 340 15.17
 Construction of accommodations and
 facilities 125 5.58
 Construction of canvass nursery ponds
 and housing 312 13.92
 Water pumps and housing 250 11.16
 Blowers and housing 250 11.16
 Traps for sampling and harvesting 1,000 4.46
 Equipment (pvc pipes, lighting,
 salinometer, thermometer, ect) 81 3.61
 Miscellaneous 251 11.16
 Interest on fixed cost 33 1.47
 Total ownership cost 2,241 100

TABLE 4.
Estimated operating costs per production cycle for the monoculture
and polyculture trials of spotted babylon in a total farm area of 0.8
ha of earthen ponds.

 Monoculture Polycultures

 Amount Amount
Items ($) % ($) %

Purchasing for juveniles
 spotted Babylon 11,200 66.10 11,200 58.32
Purchasing for juveniles
 sea bass -- -- 1,800 8.57
Fuels and lubricants 586 3.46 586 2.79
Electricity 378 2.23 378 1.80
Feed for spotted babylon 1,358 8.02 1,358 6.47
Feed for sea bass -- -- 1,920 9.14
Labor (2 full time) 1,750 10.33 1,750 8.33
Repairs and maintenance 375 2.21 375 1.79
Ice for feed storage 108 0.64 108 0.51
Interests on operating capital 1,188 7.01 1,529 7.28
Total operating cost 16,943 100 21,003 100

TABLE 5.
Estimated total cost (%) per production cycle for the monoculture
and polyculture trials of spotted babylon in a total farm area of
0.8 ha of earthen ponds.

 Monoculture Polyculture

 Amount Amount
Items ($) % ($) %

Ownership costs 2,241 11.68 2,241 9.64
 Land 500 2.61 500 2.15
 Depreciation 1,708 8.90 1,708 7.35
 Interest on investment 33 0.17 33 0.14
Operating costs 16,943 88.32 21,004 90.36
 Spotted Babylon juveniles 11,200 58.38 11,200 48.18
 Sea bass juveniles - - 1,800 7.74
 Fuel and lubricants 586 3.05 586 2.52
 Electricity 378 1.97 378 1.63
 Feed for spotted babylon 1,358 7.08 1,358 5.84
 Feed for sea bass - - 1,920 8.26
 Hired labor 1,750 9.12 1,750 7.53
 Repairs and maintenance 375 1.95 375 1.61
 Ice for storage of feed 108 0.56 108 0.47
 Interests on investment 1,188 6.19 1,529 6.58
Total cost per production cycle 19,184 100 23,245 100

TABLE 6.
Enterprise budgets of a total farm area of 5,000 [m.sup.2] for the
monoculture and polyculture trials of spotted babylon in a total
farm area of 0.8 ha of earthen ponds.

Parameters Monoculture Polyculture

Production
 Spotted Babylon (kg) 3,368 3,344
 Sea bass (kg) -- 3,920
Costs per production cycle
 Initial investment requirements 4,837 4,837
 Ownership costs ($) 2,241 2,241
 Operating costs ($) 16,943 21,004
 Total cost ($) 19,184 23,245
Returns
 Gross return ($) 30,312 37,936
 Net returns ($) 11,124 14,691

* Total yield of spotted Babylon and sea bass per production cycle
at 0.4 ha

--Price at farm gate for spotted Babylon and sea bass of $9.00 and
2.25/ kg, respectively
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Author:Natsukari, Y.
Publication:Journal of Shellfish Research
Date:Dec 1, 2006
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