Tomoe Shokai (President: Sadao Fukao) started examinations to verify prawn farming in Okinawa from April, taking advantage of the oxygen dissolving device which it handles, estimating a monthly O2 consumption of 1400 to 2700 m3.

Oxygen enrichment in fish farming is aimed generally to control concentration of dissolved oxygen in water. In case of prawns, the dissolved O2 concentration of about 10ppm in the daytime gets lower down to 4ppm or so, resulting in an unstable condition during the nighttime when their respiration becomes active. Such condition surely causes stress and diseases to prawns which are sensitive to environments. In the nighttime, it is also necessary to watch around the farming pond in order to prevent oxygen deficiency, which naturally is a burden on the fish farmers.

To this end, an optimum concentration of 8 to 10ppm must be maintained as a target by an appropriate supply of oxygen from time to time, and it is also aimed to enhance efficiency in farming by increasing the rate of growth at one fish-farming pond. Atushi Sakai of planning sales manager said, “The enhancement of production efficiency by preventing disease contributes to improvements in earnings recovery and also the reduction of burden for a look-around by sensor to monitor the concentration of dissolved oxygen.”

Tomoe implemented its verification test from June to October last year and succeeded in breeding without any problem more than 40 prawns increased from the usual number of 20 per square meter. From April the verification site is moved to Okinawa which is Japan’s biggest production area of prawns and the company challenges a large-scaled verification actually in a farm area of 3300 m2.

For information, the O2 consumption in the previous verification test was about four LGCs per month. This time expecting 20 times larger scale, the company presumes to supply using CE or PSA and estimates a monthly consumption of 1400 to 2700 m3 by means of optimizing the gas supply and water circulation system. The oxygen dissolving device, made by Daiei Seisakusho (President: Yuji Morita) of sheet metal processing company in Toyohashi City, Aichi Prefecture, dissolves water in the atmosphere of oxygen filled in the system with a unique knowhow in the technology to produce highly-concentrated O2 water of maximum 40ppm. Tomoe first started to sell the system to activate and purify the microorganisms which decomposes wastes from plants and sludge of rivers.

Since 4 to 5 years ago Tomoe has been adding its knowhow suitable for fish farming developed through researches, and extended its target to farming of eel, sturgeon, globe fish and flat fish. Particularly, the eel farm out of them took delivery of more than 100 units of the system. To grow the business in future, Tomoe has brought into view a prawn-farming business of own management, aiming at an annual sales of 500 million yen altogether including gas, equipment, piping and other peripheral facilities.