Project name: Optimization of farming technique for mollusk raft culture ecosystem in shallow sea Project types: Key Program of Chinese Academy of Sciences Project director: Yang Hongsheng, Research professor Address: Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, 7 Nanhai Road, Qingdao 266071, P. R. China E-MAIL: hshyang@ms.qdio.ac.cn Telephone and Fax: 86-532-2898582 Participant: Zhang Fusui, Professor, Institute of Oceanology, Chinese Academy of Sciences He Yichao, Professor, Institute of Oceanology, Chinese Academy of Sciences Zhou Yi, Associate professor, Institute of Oceanology, Chinese Academy of Sciences Zhang Tao, Associate professor, Institute of Oceanology, Chinese Academy of Sciences Presiding institutions: Institute of Oceanology, Chinese Academy of Sciences Duration: Sep., 1996 to June, 2000 Abstract： The industry of shellfish and seaweed raft culture has been more quickly developing in China since 1980’s, which contributed greatly to the coastal and, even the national economics. But now faced different kinds of severe challenges, because of bad management, seeking high production rate and high output value, lopsidedly and ignoring the social and ecological effectiveness, resulted in being over developed, overloaded and severely self-polluted in some farming areas, and the ecosystem shows disequilibrium, the diseases of the cultured organisms are aggravated, and cultured shellfish small in size, and high in mortality rate, and lower output. These important ecological problems have affected the development of mariculture industry in the shallow sea of China, and more strongly threatened the prospect oncoming. Focusing on the problems above, the monoculture pattern of the scallop Chlamys farreri , and polyculture patterns of the scallop and the kelp Laminaria japonica, and that of the scallop, the kelp and the sea cucumber Apostichopus japonicus, which were stocked with different densities, were designed and established with nine culture and one control ecosystems, according to the findings of shellfish experimental ecology in labrotray and the investigation results of the nutrient dynamics, primary productivity and food aviabilitity, and the status quo of shellfish and seaweed cultured in Sishiliwan Bay, Yantai,. After being measured and assessed, the carrying capacities of the cultured organisms were preliminary evaluated, and some farming patterns were optimized for future research and practice. The main results of this studies are listed as fellows: The carrying capacities of the scallop C. farreri, the kelp L. japonica, and the sea cucumber A. japonicus of Sishiliwan Bay, Yantai, China, were measured semi-in situ from April 5,1998 to June 23,1998. According to the investigation results of the nutrient dynamics, primary productivity and food availability, and status quo of shellfish and seaweed culture in Sishiliwan Bay from May, 1997 to May, 1998, nine ecosystems used for culture and one for control were designed and established with ten breeding tanks in a breeding factory near the bay, in which the scallops only, the scallops and the kelps, the scallops, the kelps and the sea cucumbers with different densities were stocked. The seawater was pumped from the bay 4 times and the exchanging quantity was 100% per day in each ecosystem. Water temperature, dissolved oxygen concentration, pH, and salinity were determined two times daily at 5:00 am and 17:00 pm, and the instantaneous growth rates and the survival rates of the cultured organisms were measured per fifteen days. In this experiment, it was defined that the maximum standing stock in the normal environment when the instantaneous growth rate of one species cultured in an ecosystem reached to naught would be able to stand for the carrying capacity of the ecosystem for the species. The results show that the carrying capacities of the scallops in monoculture ecosystems, and in the polyculture ecosystems of shellfish, seaweed and sea cucumbers are 184.6g/m2 and 201.7g/m2, separately, the capacities of the kelps in the polyculture ecosystems of shellfish and seaweed, and in the polyculture ecosystems of shellfish, seaweed and sea cucumber are 101.8g/m2 and 106.8g/m2, respectively, and that of sea cucumber in the polyculture ecosystems of shellfish, seaweed and sea cucumber is 74.7 g/m2. Using the experimental results for Sishiliwan Bay whole, the carrying capacities of the scallops in monoculture pattern, and in the polyculture pattern of shellfish, seaweed and sea cucumber are 7387.7 kg/ha and 8072.0 kg/ha, separately, and the capacities of the kelps in the polyculture pattern of shellfish and seaweed, and in the polyculture pattern of shellfish, seaweed and sea cucumber are 4072.0kg/ha and 4272.0 kg/ha, respectively, and that of sea cucumbers in the polyculture pattern of shellfish, seaweed and sea cucumber is 597.9 kg/ha. The production efficiency of different mariculture patterns in the shallow sea of Sishiliwan Bay, Yantai, China, were comparatively semi-in situ studied from April 5,1998 to June 23,1998. In the experiment, nine ecosystems used for culture and one for control were established, and described as above. In this experiment, it was defined that the maximum daily production of one species cultured in an ecosystem would stand for the productivity of the ecosystem for the species. The results show that the productivities of the scallops in monoculture ecosystems, and in the polyculture ecosystems of shellfish, seaweed and sea cucumbers are 0.56g/m2.d and 0.78g/m2.d, respectively, and that of sea cucumbers in the polyculture ecosystems of shellfish, seaweed and sea cucumbers is 0.70 g/m2. The growth rate of the scallops in the monoculture ecosystems is slower than that in the polyculture pattern of shellfish and seaweed, and in the polyculture pattern of shellfish, seaweed and sea cucumbers ecosystems. The efficiency of the polyculture pattern of shellfish, seaweed and sea cucumber is better than that of the shellfish monoculture and the polyculture pattern of shellfish and seaweed. The optimal stocking rate for the scallops in monoculture pattern, and in the polyculture pattern of shellfish, seaweed and sea cucumbers are 21.0 and 23.0 ind./m2, respectively, and the optimal for the kelps in the polyculture pattern of shellfish and seaweed, and the polyculture pattern of shellfish, seaweed and sea cucumber are 0.68 ind./ m2 and 0.71 ind./ m2, respectively, and that of sea cucumbers in the polyculture pattern of shellfish, seaweed and sea cucumbers is 2.0 ind./m2. KEY WORDS Optimization of mariculture technique, Chlamys farreri, Laminaria japonica, Apostichopus japonicus, Shallow sea