Introduction
Sea cucumber, Apostichopus japonicas, has become an important species cultured in the northern part of China including Liaoning, Shandong and Hebei provinces, and has gradually expanded towards the southern part including Fujian, Guangdong and Hainan provinces (Chen, 2004). Recently, under the stimulation of large profits, capital investment has been continuously flowing into the sector and farming areas have sharply expanded. Sea cucumbers are deposit-feeders that ingest sediment with organic matter (Yingst, 1976; Yingst, 1982; Hudson et al., 2005; Uthicke and Karezc, 1999; Michio et al., 2003). The coastal zone bears most of the ecological consequences of aquaculture development (Primavera, 2006).There has been much emphasis on developing sustainable approaches for aquaculture, such as integrated culture and zero discharge aquaculture system. In comparison with the other species, sea cucumber is no extra-feed and better to environment. Kang et al (Kang et al., 2003) considered that abalone cocultured with sea cucumber could reduce the level of inorganic nitrogen in the water and consequently promoted the growth. Bivalves (Zhou et al., 2006), shrimp (Purcell et al., 2006), and green-lipped mussel (Slater and Carton, 2007) cocultured with sea cucumber were proved to be beneficial, too.

The commercialization of sea cucumber farming, which was stimulated by the outbreak of shrimp disease, has begun since 1990s. However, the methods and model of sea cucumber culture lacked diversity, relying mainly on extensive culture. Lower production but higher price limited the development of sea cucumber industry.

Many studies were conducted on sea cucumber in the respects of its economic value, culture methods and physiological mechanism. Nevertheless, there were few researches about the economic benefit and investment risk of sea cucumber culture. The aim of the study is to carry out a bio-economic evaluation of sea cucumber in the earthen ponds so as to provide reliable data for investors.

1 Methods

1.1 Bio-economic model

The bio-economic model of sea cucumber culture is shown in Figure 1. The economic income was influenced by the culture technique and market price. The whole culture period of sea cucumber was mainly determined by the size of juvenile. Juveniles at the size of 2-15g/ind., 15-30g/ind. and 30-60g/ind. need be cultured 2.5 year, 1.5 year and 1 year, respectively. However, the input and survival rate were different as the size of juvenile varied.

Figure 1 Bio-economic model of sea cucumber culture

 

1.2 Data source

All financial data in the present study were collected from three commercial sea cucumber farms located in Ru Shan, Wei Hai, Shan Dong provinces, China. Three earthen ponds of 0.5 ha, 2.2 ha and 1.2 ha for sea cucumber culture were selected. Data concerning sea cucumber culture, product price, economic income and expenditure cost were collected from a three-year observation (from 01/2008 to 05/2011). The investment on all the culture farms was self-financed by the investors.

1.3 Economic evaluation

The income and cost of the fourth and fifth year were estimated based on the first three-year data. The data was plotted graphically using linear regression analysis to identify any possible trends between market price per unit and that per unit size. However, it is difficult to forecast the price for two more years; thus the price of the fifth year was used for calculating the income and output of that of the sixth to tenth year.

Table 1 summarizes a range of data collected during the culture period in order to obtain accurate and valid bio-economic evaluation of the farms. Net present value (NPV), internal rate of return (IRR) and discounted payback period were the main parameters for the evaluation of the economic income. For the experimental data, various assumptions are made in order to simplify the study and underscore the focus of the research (Table 2).

Table 1 Parameters monitored in sea cucumber (Apostichopus japonicas) farm (Ionno et al., 2006)

Table 2 Data obtained from the three sea cucumber ponds

2 Results

2.1 Construction cost and operating cost of the three ponds

The construction cost of sea cucumber ponds increased in linear with varied size of the pond (Figure 2). The relationship between the total input during the three years and pond size can be described by the equation of y = 143490Ln(x) + 405559 (Figure 3), while the relationship between the input of juvenile sea cucumber and pond size can be represented by the equation of y = 42332Ln(x) + 82695 (Figure 4). Juveniles of sea cucumber at different size of 2 g, 25 g and 50 g per ind. required different prices; however, they all presented with a linear trend (Figure 5).

Figure 2 Variation of construction cost with size of pond

Figure 3 Variation of total input with size of pond during the three-year culture

 

Figure 4 Variation of total input of juvenile sea cucumber with size of pond

 

Figure 5 Fluctuation of price of sea cucumber during 2007~2011

2.2 Cost and benefit

The cost and benefit of sea cucumber culture in the three ponds were described in Table 3, Table 4 and Table 5. The data of year 1 to year 3 of the three ponds were gained throughout the culture period. The cost and benefit of year 4 to year 5 were estimated based on the trend of the first three years’ data. The data of year 6 to year 10 came from those of year 5. The inflation of labor cost, electricity cost, construction cost and chemical/cleaning product cost were not included.

Table 3 Benefit and cost of sea cucumber cultured in 0.5-ha pond

 

Table 4 Benefit and cost of sea cucumber cultured in 1.2-ha pond

 

Table 5 Benefit and cost of sea cucumber cultured in 2.3-ha pond

2.3 IRR, NPV, and payback period

IRR, NPV and payback period in ten-year period were shown in Table 6. Net present value of the sea cucumber ponds increased with the increasing pond size, obviously higher than that in the other industries. However, the internal return rate dropped at the pond size of 1.20 ha. The payback periods of three ponds were all less than 4 years (Table 5).

Table 6 IRR, NPV and payback period of the three ponds in ten year period

Zhou Y., Yang H., Liu S., Yuan X., Mao Y., Ying Liu, Xu X., and Zhang F., 2006, Feeding and growth on bivalve biodeposits by the deposit feeder Stichopus japonicus Selenka (Echinodermata: Holothuroidea) co-cultured in lantern nets, Aquaculture, 256: 510-520
http://dx.doi.org/10.1016/j.aquaculture.2006.02.005