Growth Acceleration of Fish and Shellfish by Discharge Plasma Treated Air*

Food problems around the world are becoming more severe year by year. One way to solve the food problem is through breeding, but people strongly resist genetic modification. Since it is tough to grow fish and shellfish in a completely closed system, and most are farmed in natural environments, it is preferable not to tamper with their genomes. If we could promote the growth of fish and shellfish without tampering with their genomes, we could increase production efficiency without raising resistance among consumers. Our research aimed to pioneer a novel technology that stimulates the growth of fish and shellfish by treating them with active species generated by discharge plasma.

Plasma-treated gas containing active species such as nitric oxide (NO) was generated via an arc discharge in the atmosphere and inserted into an aquarium containing Nile tilapia. No ozone was detected in the plasma-treated gas. The supply duration of plasma-treated air to the water tank was 0.5, 2, 5, and 15 min. Tanks were prepared for each of these four conditions. The plasma-treated gas was supplied daily at the same hour. We observed that when plasma-treated gas was supplied to tilapia from the 16th week of age for 5 minutes daily, the average length of the fish at 31 weeks of age was about 1.5 times longer than that of the control fish. We found that plasma treatment enhances growth in average values for all other supply time conditions. Individual differences in body size were more evident under conditions of 15 min feeding time. One of the fish had more restrained growth than the control. This means that an excessive supply of active species may cause growth inhibition. Similar results are obtained for shellfish. In conclusion, our research shows that by supplying optimal plasma-treated gas brings a growth-promoting effect on fish and shellfish.