38 MARCH 2018 • WORLD AQUACULTURE • WWW.WAS.ORG polyurethane foam to maintain room temperature and to protect from corrosion by seawater. Species Selection for Culture in RAS Climate and local markets are considered the key criteria for fish species selection in RAS culture. Thus, coldwater, low marketpriced, fast swimming (with low FCR) fish species should not be cultured in the Bohai Bay region. Warmwater species of groupers are well known for having an attractive market price and high demand in the local market, with a daily demand of about 4000 kg of live fish. Locally cultured groupers are more competitive in the market than those transported from southern China. In grouper RAS (Fig. 9), the water is heated to 25 C during the cold season (October-April) using 70 C geothermal water. Groupers grow to market size (600-800 g) after one year of rearing at a maximum density of 40 kg/m3. Half-smooth tongue sole is a high-value indigenous fish species of the Bohai Bay area. Catches are very limited and the fish cannot be cultured in southern China or in cages. In RAS culture (Fig. 10), water temperature is warmed to 21-23 C using geothermal water during the four-month low-temperature period and cooled during the four-month hot season. The market size of sole ranges from 500 g to 2.5 kg after a culture period of ten months to two years at maximum biomass density of 25 kg/m3. The RAS design of marine fish growout farms in Bohai Bay is successful as the result of comprehensive consideration of advantageous conditions such as a large live fish market, acceptable labor costs, rich and cheap natural geothermal water resources, as well as disadvantageous conditions such as the high price of electricity, turbid seawater and extreme climate and weather. The technical innovation of recirculating aquaculture plays an important role in the growout of marine fish in Bohai Bay. Oversizing the biofilter might favor a very stable microflora with good balance between K- and r-strategists, preventing opportunistic Vibrios from reaching critical (quorum-sensing) densities and eventually activating virulence. Acknowledgements Xin Naihong has received support from Earmarked Fund Innovation Team of Tianjin Fisheries Research System (201717). Notes Naihong Xin, Salt Research Institute, CNSIC, Tianjin 300450, China, xinnaihong@aliyun.com Shusen Zhang and Yonghai Yang, Tianjin Haifa Seafood Industrial Development Co., ltd., Tianjin 300452, China Liying Sui, Tianjin University of Science and Technology, Tianjin 300457, China Kezhi Xing, Tianjin Agricultural University, Tianjin 300384, China Patrick Sorgeloos, Ghent University, B-9000 Gent, Belgium FIGURE 7. Interior view of the RAS system showing production tanks. FIGURE 8. Live fish sales. FIGURE 9. Grouper Epinephelus coioides culture in a RAS system. FIGURE 10. Half-smooth tongue sole Cynoglossus semilaevis culture in a RAS system.
RkJQdWJsaXNoZXIy MjExNDY=