| The Qiansan Islets of Haizhou Bay were chosen for the ecological aquaculture of scallop Chlamys farreri. The geography, hydrology, environmental quality and food supply capacity were studied from May 2007 to June 2008. The clearance rate was estimated in situ, and the carrying capacity was evaluated by the actual growth rate of C.farreri and hydrology of the area. Survival, growth and immunity activities were studied at different culture depths and with different culture methods. The predation of scallop by crab Charybdis japonica and seastar Asterias amurensis were also studied, both in situ and in the laboratory. All of this yielded information on the best way to culture C. farreri in this area. The results are as follows:1.The sea water quality was very high, and although the food quantity is low in the seawater, the high current speed can make up for lack of food concentration. The environmental parameters varied with water depth, so that culture methods need to be adjusted in terms of the actual situation to obtain a better quality of shellfish products.2.The growth of scallop Chlamys farreri suspended in deep water of Haizhou Bay were studied from July 2007 to June 2008; and the biodeposition method was used to estimate the clearance rate of C. farreri under field conditions. Results showed that the scallop grew fast during all the culture time, with the exception of summer. The average growth rate of dry tissue weight was 11.29 mg/d, and that of dry shell weight was 48.84 mg/d, the scallop reaching commercial size (6cm in shell height) at the beginning of the second year. The clearance rate is influenced significantly by water temperature and scallop size. It increased with a rise in water temperature for the same scallop size, and it likewise increased with an increase in scallop size under constant water temperature. Using the improved Incze et al. (1981) model to evaluate the carrying capacity of scallop cultured in the area,we found that area lengths suitable for scallop culture along the current direction at different times were 4.0, 4.6, 4.7, 5.1, 4.5 and 3.2 km respectively, with an average value of 4.35 km.3.The survival, growth, and immune response of C. farreri cultured in lantern nets at 5 different depths (2, 5, 10, 15, and 20 m below the sea surface) were studied in Haizhou Bay during summer and autumn, 2007. The survival and growth rates of the scallops were quantified bimonthly. Immune activities in haemolymph (superoxide dismutase (SOD) and acid phosphatase (ACP)) were measured to evaluate their health at the end of the study. Environmental parameters at the 5 depths also were monitored during the experiment. The mortality of the scallops mainly occurred during summer, and their survival when suspended at 15 m (78.0%) and 20 m (86.7%) was significantly higher than at 2 m (62.9%), 5 m (60.8%), and 10 m (66.8%) at the end of this study. The mean shell height growth rate was significantly faster at 10 m (205.0μm/d) and 20 m (236.9μm/d) than at 2, 5, and 15 m in summer (July 9 to September 1); but the shell growth rate at 20 m was significantly lower than at the other 4 depths in autumn (September 2 to November 6). In contrast with summer, the scallops at 5 m grew the fastest (262.9μm/d) during autumn. The growth of soft tissue at different depths manifested a trend similar to that of the shells. There was a faster growth rate of shell height and soft tissue in autumn than in summer, with the exception of the shell height at 20 m. The SOD activity of the scallops increased with depth, and the ACP activity was significantly higher at 15 and 20 m than at other depths, which suggests that scallops were healthier near the bottom. Factors explaining the depth-related mortality and growth of scallops are also discussed.4.We examined the growth, survival, and immune response of C. farreri, during a 1- year period in deep water of Haizhou Bay. Scallops were cultured using two methods, (1) in lantern nets at 5 m depth, and (2) in bottom culture system (sleeves) on the seabed. Shell height, meat dry weight, and immune activities in haemolymph (superoxide dismutase (SOD) and myeloperoxidase (MPO)) were quantified bimonthly or quarterly from July 2007 to June 2008. Survival was measured at the end of the study, and environmental parameters in the experimental layers were monitored during the experiment. The growth and immune activities of the scallops were lower during summer than at other periods, and the main mortality occurring in summer and autumn. The growth and immunity of the scallops were higher in suspended culture than in bottom culture during the experiment, with the exception of shell growth during the last study period. The survival of scallops in suspended culture (54.6±12.3 %) was significantly lower than in bottom culture (86.8±3.5 %) at the end of the study. We conclude from our results that high mortality of C. farreri can be prevented by culturing them in the bottom culture system during summer and autumn and then transferring them to suspended culture to improve scallop production.5.The predation of C. farreri by crab Charybdis japonica and seastar Asterias amurensis was examined in situ and in the laboratory at different water temperatures. Results showed that the predation rate of small scallop (shell height<5.0 cm) increased with increasing water temperature, but that predation is negligible when the shell height of scallop exceeded 5.9 cm and also when the water temperature is lower than 10℃. The in situ predation rate was higher than in the laboratory with the same seawater temperature, but the Q10 values were similar in the two different methods. The best way to enhance the survival of bottom cultured C. farreri is to seed large scallops in autumn and winter when the water temperature is low.
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