| A series of outdoor experiments were conducted to investigate the optimal culture model of sea cucumber (Apostichopus japonicus selenka) in earthen ponds. We investigated optimal shelters, optimal stocking densities, polyculture with different sea cucumber sizes, experimental studies on polyculture of sea cucumber with shrimp (Fenneropenaeus chinensis Osbeck), and the effect on polyculture of sea cucumber with scallop (Chlamys Farreri Jones & Preston). The main results were presented as the followings:1,Effects of Shelter Types on the Growth and Survival Rate of Sea Cucumber, Apostichopus japonicus, in Earthen PondShelter is a type of farming equipment especially used in sea cucumber pond and sea ranching, and it could provide habit and natural food for sea cucumber. This study was conducted in twenty 8m (L)×8m (W)×2m (H) net enclosures to investigate the optimal shelter through measuring the growth, survivorship and yields of sea cucumber (Apostichopus japonicus Selenka) with initial size of 5.0±2.0 g at different shelter types of stone (ST), cement pipe (CP), earthenware (EA), brick (BR), and plastic pipe (PL) from 20th May 2007 to 20th April 2008. Results showed that the numbers of bacteria on the shelters were significantly different among shelter types and were higher in Nov. 2007 than in May 2008. The highest survival rate and growth rate of sea cucumber were gained in ST and BR respectively; the yields of sea cucumber in BR and ST were significantly higher than in the other shelters. Based on these results, it could be concluded that BR shelter was the best one for the sea cucumber culture among the five popular shelter types.2,Optimal stocking density of farmed sea cucumber, Apostichopus japonicus Selenka, under the conditions of supplement feeding and unfedThe study was conducted in thirty 8m (L)×8m (W)×2m (H) net enclosures to investigate the optimal stocking density for growth, survival and production of the sea cucumber. The initial weight was 5.0±2.0 g and the stocking densities were 5, 10, 15, 25 and 35 ind m-2 under the conditions of supplement feeding and unfed from 20th May 2007 to 20th April 2008. The results showed that a large weight loss in the aestivation phase (AE) occurred, and sea cucumbers grew slowly during the winter phase (WT), and grew rapidly during the spring phase (SP) and the autumn phase (AU). Supplement feeding could promote growth of sea cucumber (P < 0.05). However, there was no significant difference in survival rates between different feeding regimes, though average survival rates of sea cucumber with supplement feeding was slightly higher than those unfed. With the increase of stocking densities, specific growth rate decreased from 3.4 to 1.1 % day-1. The optimal stocking density was 22.3 and 14.1 inds. m-2 for the supplement feeding condition and the unfed condition, respectively.3,The experimental studies on polyculture of different size of sea cucumbersIn present study, the available of polyculture different sizes sea cucumbers together was investigated with indoor and outdoor experiment to achieve commercial size sea cucumbers every year. The results showed that the specific growth rate of sea cucumber in polyculture was lower than those in monoculture; however, the total yield in polyculture was higher than in monoculture. Sea cucumber with 1g ind-1and 30g ind-1 body weight could polycultured together, and individuals with initial body weight of 30g ind-1 got to commercial size and 1g ind-1 gtowth to 30g after one year rearing, and then juvenile sea cucumber with initial body weight of 1g could be added again. Supplement 1g ind-1 juvenile sea cucumber was stocked. With this method, commercial size sea cucumbers could be harvested every year.4,The experimental studies on polyculture sea cucumber with shrimp (Fenneropenaeus chinensis Osbeck)The study investigated the polyculture of sea cucumber with shrimp in net enclosure during 330d culture period. The result showed that there was nosignificant difference in survival rate and growth of sea cucumber among different stock densities of shrimp. However, the size and survival rate of shrimp with stocking densities increasing decreased significantly. The optimal stocking density of sea cucumber (about 5g) and shrimp (about 0.8) is 15ind. m-2 and 4ind. m-2 which could gain the maximum production and economic income of sea cucumber. 5,The experimental studies on polyculture sea cucumber with scallop (Chlamys Farreri Jones & Preston)The effect of polyculture sea cucumber with scallop was studied. Sixteen net enclosures were stocked randomly at densities of 0 and 3.75 ind. m-2 scallop and 10 and 15 ind. m-2. The result showed there was no significant difference in growth and survival rate of among different densities of sea cucumbers (P > 0.05). However, sea cucumbers which polyculture with scallop grew faster than mono culture of sea cucumbers significantly (P < 0.05). Polyculture scallops in spring and autumn with sea cucumbers increased the production significantly (P < 0.05). The optimal stocking densities of sea cucumber and scallop are 15 ind.m-2 and 3.75 ind.m-2, respectively.6,Analysis of sustainability of sea cucumber culturing in earthen pond of China using the EMERGY approachThe economic income and environmental sustainability of sea cucumber culture in northern China was analyzed using EMERGY approach. Schematic diagram of sea cucumber ponds with EMERGY symbols was built to analysis the EMERGY of different part in sea cucumber earthen ponds. EMERGY Yield Ratio (EYR), EMERGY Loading Ratio (ELR) and EMERGY Sustainable Index (ESI) was selected to evaluate the sustainability and carrying capacity of sea cucumber ponds and several integrated fish and shrimp culture model, the results showed that EYR in sea cucumber culture was higher than integrated fish and shrimp culture, and sea cucumber culture gained higher sustainability and carrying capacity.
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