Tomoe Shokai is carrying out a verification test of oxygen-enriched farming of Japanese tiger prawn at Itanma Farming Center (President: Akira Terukina) of Nanjo City, Okinawa, utilizing the oxygen dissolution equipment supplied by Tomoe.

The verification test for one year from May 2016 to April 2017 is aimed to research effects appearing in the growth rate or pace of prawn in comparison with the farming pond without oxygen enrichment. As the Japanese tiger prawn is nocturnal, the oxygen concentration in the sea goes down in the night time when their breathing becomes active. The prawn is so sensitive to any such environmental change that the low concentration may cause their diseases. The oxygen supply at night is intended to enhance the yield of growth promotion. For the verification implemented this time oxygen is supplied using PSA and oxygen dissolution equipment. From 5:00 p.m. to 8:00 a.m. on the next day, namely from the sunset to dawn when the prawn is active, water pumped up from the farming pond then mixed with the oxygen supplied by PSA and returned to the pond as a structural routine.

One unit of PSA (capacity: 3m3/h) made by Advance Riken is employed, and three units of oxygen dissolution equipment made by Daiei Seisakusho (President Yuji Morita, headquartered in Aichi) are in operation with the addition of Tomoe’s own knowhow, of which monthly oxygen consumption amounts to about 1200m3.

The prawn under verification in Okinawa was caught at the end of 2016 and it seems that there apparently was an effect of oxygen. President Terukina is satisfied to say, “The growth number increased by 40% comparing with last year. In some cases growth is disturbed by an increase of the number, but at the moment the prawns are growing at a good pace. The average weight of the prawn caught in this season is 20g as standard, but in this season with oxygen many prawns are seen large-sized.”

In this farming center, apart from the application into the farming pond, oxygen is also added to the water tanks loaded on ships or forklifts for landing catches and temporary tanks to keep prawns in the sorting process before packing into boxes, so that prawns may not be weakened until delivery. For this purpose cylinders are used. The approximate consumption of oxygen is one cylinder per three days.

Tomoe Shokai started to sell oxygen dissolution equipment for fish farming about five years ago, and has already delivered more than 100 units to the eel, halibut and globe-fish farmers.