The approach to large-scale fishery seed production has been accelerated along with positive promotion of aquaculture. The technology for mass and stable production of the initial feed organisms using the mass culture tank is necessary for the large scale production of the fishery seedlings. The clarification of the light penetration in the culture tank attenuation with the increase of the cultured microalgal density and the light irradiation distance make setting and controlling optical radiant environment be a concern of the photosynthetic activity of microalgae in general. Measurement and analysis of the attenuation of optical penetration in the culture tank were conducted with the increase of the microalgal density and the light irradiation distance. As a result, it was found that the reduction of optical radiation is proximate to the law of Lambert-Beer within the range of 5 × 10⁵ ∼ 1 × 10⁷ cells ml^-1 of practicable density, and 14 ∼ 24 cm of liquid thickness. The practical mass culture tank could be designed by the simulation of optical environment according to the law.

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Trials of individual rearing of tilapia Oreochromis niloticus were carried out as the feasibility experiments of fish culture using cartridge type tanks. And for the development of the cartridge type tank, a reasonable tank size was examined. Tilapia (average weight 4.5 g) were individually raised for four weeks in the small acrylic aquaria: height of rearing area is 50 mm, depth is 100 mm, and widths are 20, 25, 30, 35 and 40 mm. Some of diets flowed out through drainage tube of the aquaria, and were lost. The ratio of lost diets was large in the 20 mm-width aquaria, in which fishes were not able to turn around. Specific growth rates (SGR) in 25, 30, 35 and 40 mm-aquaria were almost equal, although SGR in 20 mm-aquaria was lower than them. These differences should be influenced by ratio of lost diets. These results suggested that the most important problem in the development of the cartridge type fish culture system for aquaculture factory is avoidance of feed loss, and the width of cartridge type tank can be reduced into two times the width of the fish.

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A comparison of methods to detect and diagnosis Cucumber mosaic virus by using enzyme-linked immunosorbent assays (ELISA) and an Immunocapture Reverse Transcriptase Polymerase Chain Reaction (IC-RT-PCR) was made to determine the detection limit of each method. We produced monoclonal antibodies for two Japanese strains Pepo, M2-Cucumber mosaic virus (CMV) as antigens. Tests to detect the pure virus protein with ELISA and IC-RT-PCR were performed and IC-RT-PCR was found to be more sensitive, reaching 10 pg/ml for the pure virus protein, while ELISA method levels were 0.7 ng/ml. Furthermore, we concluded that the present method is very useful for the diagnosis of infected plants.

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We are planning to develop a new food production system using Euglena, a photosynthetic microalgae, replacing higher plants to feed the rapidly increasing global population. In this study, we evaluated the quantum yield of Euglena and proved that Euglena is a more effective food source than higher plants. Euglena was cultured under three light conditions of red and blue light emitting diodes (LEDs) and white fluorescent lamps, aerated with the addition of 0.04 and 10% CO₂, respectively. We measured cell numbers, dry weight, and carbon concentration everyday. The quantum yield (QY) was calculated at the log phase. QY=the quantity of energy for carbon fixation/photon energy. As a result, we found that the optimal light conditions of the white fluorescent lamp for the quantum yield of CO₂ fixation was 30 μmol m^-2 s^-1, aerated with the addition of 10% CO₂. We found that the optimal light conditions of LEDs were 30 μmol m^-2 s^-1, aerated with the addition of 10% CO₂, as well as a red:blue photon ratio of 9:1. The QY of Euglena under LED light conditions reached 14%, higher than that of higher plants (under 11%, theoretically). We concluded that the quantum yield of Euglena was greater than that of higher plants. We will further investigate other basic data of Euglena as a food production system.

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18-days-old tilapia fry (Oreochromis niloticus) were raised for 15 days in various artificial aquaculture waters (AAWs), which are eight compositions of isotonic saline mediums (AAW-1 to 8) and an artificial freshwater (AAW-9). All of fry reared in isotonic mediums lack potassium (AAW-2 and 8) had been died until seventh day, although fry in the other AAWs exhibited high survival rates. It was suggested that tilapia fry can not tolerate low level of potassium at relative high salinity. The specific growth rate of tilapia in AAW-9 was slightly better than the others, but not significantly. The reason why fry in isotonic medium showed reduced SGR was assumed that increase of energy cost for saline adaptation exceeded decrease of energy cost for osmoregulation in 15 days of experimental period. The optimum age at transfer to AAW must be examined thoroughly to minimize energy cost of saline adaptation and enhance growth performance.

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