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Ulsan, South Korea

Kim T.,Chonnam National University | Yoon H.-S.,Chonnam National University | Shin S.,Chonnam National University | Oh M.-H.,SubOcean Co. | And 4 more authors.
Aquaculture | Year: 2015

The co-culture potential of juvenile abalone with sea cucumbers presents a simple yet tremendous opportunity to expand existing monoculture techniques. Both products have substantial market demand and if the wastes of the abalone can be used as food for the sea cucumber, then both economic and sustainability goals could be addressed. Designing a simple but effective containment structure suitable for both animals, however, requires both engineering and scientific approaches. The first objective of this study was to investigate the flow field and dissolved oxygen exchange within two potential structure designs using computational fluid dynamics (CFD). The second objective was to conduct a laboratory experiment, with the same containment structures, to determine if the sea cucumbers would use organic matter (food residues and feces) as a food source produced from the abalone and would show positive growth rates. The design of both containment structures included surfaces for both species to reside and move around. One of the structures utilized vertical plates with access holes between sections (called the UC) while the other was a combination of tube and plate sections (called the TC). The procedure included placing both structures in separate seawater flow through tank systems each with juvenile abalone and sea cucumbers for 7. months. The intent was to examine the growth rates of each set of animals under the same, external flow field conditions. During the experiments, only the abalone was fed.The CFD calculations were verified with tank measurements and indicated better dissolved oxygen exchange in the UC structure. Results of the sea cucumber growth experiments showed that the animals in the UC structure grew to 7.50. g from an initial wet weight value of 3.37. g. In the TC structure, however, the results were not as promising with total growth measured at 1.4. g from an initial wet weight of 3.61. g.During the 202. day experiment, specific growth rates of 0.40 and -. 0.47% in the UC and TC, were calculated respectively. For the abalone, a statistically significant growth rate difference was not evident between the containment structures. The study also found that the juvenile sea cucumber actually fed on biodeposits from the abalone and that the substantial difference in growth rates between structure types was due to the better flow rate in the UC. © 2014 Elsevier B.V. Source

Kim T.,Chonnam National University | Kim T.,SubOcean Co. | Hwang K.-S.,SubOcean Co. | Oh M.-H.,Chonnam National University | And 2 more authors.
IEEE Journal of Oceanic Engineering | Year: 2014

A novel and fully automatic rigid fish cage system has recently been developed for deployment in the waters of Korea. The cage structure has 12 sides, incorporating a steel framework with a diameter and depth of 5.92 and 2.91 m, respectively. Attached to the steel framework is a housing for motor valves controlling variable ballast tanks, eight housings for two air compressors, a main control system, four batteries, a reserve air tank, four high air pressure tanks, 12 variable ballast tanks, and a seawater pump housing. The net of the fish cage is tightened across the frame to minimize volume reduction due to currents. The cage is outfitted with a control station located above the valve housing. With the control system, the buoyancy can be adjusted by utilizing compressed air stored in the four high air pressure tanks. The mechanical components of the ballast systems are operated by automated software that incorporates control and monitoring algorithms. The software initiates control of the ballasting components so the fish cage system can submerge if a preselected sea state occurs. The automatic control station incorporates a wind gauge, wireless communication printed circuit boards (PCBs), and a transmitting antenna. During operation, it monitors the wind speed, so the cage can be submerged before extreme sea states and then surfaced after the weather has passed and the conditions are considered safe. The control station also regulates the flow of air and seawater to and from the variable ballast tanks in response to the surface environmental conditions. Control can also be done remotely by a facility operator. In the development process, in situ tests were conducted to assess the performance of the submersion mechanism and the reliability of the automatic control system with a 1/4 size fish cage of similar construction. During the tests, the vertical position and inclination of the fish cage in the water column were measured. During the tests, the close/open states of the motor valves that control the 12 variable ballast tanks were also assessed during descent and ascent operations. The successful performance of the 1/4 size fish cage during the tests showed promise that such a system could possibly be used on a much larger scale to avoid the rigors of the environment in support of commercial level offshore aquaculture. © 2014 IEEE. Source

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