9:45 AM - 10:00 AM
[AOS13-04] Aquaculture in Space
Keywords:Aquaculture, Food chain, Gravitational environment, Material flow
For human beings to carry out activities outside of the earth, it is necessary to maintain their lives by making full use of various technologies. Especially for living on Mars or other planets, where it is difficult to smoothly supply resources from the earth due to the distance from the earth, a controlled ecosystem life support system CELSS that provides the place of human habitat and produces food with material recycling is necessary. Among them, food production is responsible not only for food supply but also for waste reuse and oxygen regeneration. Many plant cultivation studies have been conducted on the earth and in orbit, likewise, in animal experiments under microgravity, various experiments using fish have been carried out for a long time, and raring techniques including the development of rearing equipment have been established, and the fish has been shown that they are highly adaptable to space environment. Therefore, experimental studies with the aim of developing a higher-order food production technology of supplying animal protein by applying fish farming in space have been conducted. These studies are related to the production of edible aquatic organisms while performing material recirculation using the food chain, and to understand the biological characteristics contributed to the rearing technics of the applied aquatic organisms including swimming and feeding behaviors under different gravity environments.
Our studies were aimed at producing of the edible fish, tilapia Oreochromis niloticus. First, in the study of fish rearing with material recirculation, culture experiments were conducted using the rearing wastewater and solid sediments discharged from tilapia as fertilizers for culturing of the microalgae Chlorella vulgaris as the food for water flea Moina macrocopa, the water flea fed on Chlorella and then the tilapia fries were produced by propagation the water flea as food for the fish. The assumed material flow from tilapia waste to their juveniles was analyzed using these experimental data. These results showed that 5.17% of nitrogen and 5.54% of phosphorus excreted from reared tilapia are accumulated in tilapia fry in one food chain cycle. In addition, aquaponics, which uses tilapia rearing water as liquid fertilizer for hydroponic cultivation of vegetables, has been studied for a long time, and the use of these complex food production technologies also will be able to enrich the food situation in space.
Next, experiments using aircraft on tilapia's swimming and feeding behavior under different gravity was conducted. An attempt was made to shoot the video images of swimming behavior by using a closed recirculation-type fish observation device equipped with an artificial lung for oxygen supply was installed to the aircraft. As a result, under visible light irradiation, most of the individuals showed normal swimming due to the dorsal light response that turned their back to the light. It was also found that when irradiated with a near-infrared light LED (emission wavelength: 950 nm), it exhibits abnormal swimming behavior, such as rolling that rotates toward the lateral side around the body axis and looping that rotates toward the anterior around ventral side. It was also clarified that swimming and feeding are possible by irradiating visible light from one direction even under microgravity. In a gravity sensing experiment conducted by creating different gravity environment from micro to 0.2G by a similar aircraft experiment, it is possible to maintain their posture from about 0.1G, and under 0.2G, almost all individuals swim normally even without light irradiation.
From these results, it was possible to clarify a part of the material flow when performing material recycle aquaculture with tilapia in space, and it was suggested that tilapia show the normal swimming and is possible by fully adapting to the gravity of the moon and Mars.
In the future, it is necessary to study aquaculture technology with a view to alternation of generations, assuming long-term fish breeding.
Our studies were aimed at producing of the edible fish, tilapia Oreochromis niloticus. First, in the study of fish rearing with material recirculation, culture experiments were conducted using the rearing wastewater and solid sediments discharged from tilapia as fertilizers for culturing of the microalgae Chlorella vulgaris as the food for water flea Moina macrocopa, the water flea fed on Chlorella and then the tilapia fries were produced by propagation the water flea as food for the fish. The assumed material flow from tilapia waste to their juveniles was analyzed using these experimental data. These results showed that 5.17% of nitrogen and 5.54% of phosphorus excreted from reared tilapia are accumulated in tilapia fry in one food chain cycle. In addition, aquaponics, which uses tilapia rearing water as liquid fertilizer for hydroponic cultivation of vegetables, has been studied for a long time, and the use of these complex food production technologies also will be able to enrich the food situation in space.
Next, experiments using aircraft on tilapia's swimming and feeding behavior under different gravity was conducted. An attempt was made to shoot the video images of swimming behavior by using a closed recirculation-type fish observation device equipped with an artificial lung for oxygen supply was installed to the aircraft. As a result, under visible light irradiation, most of the individuals showed normal swimming due to the dorsal light response that turned their back to the light. It was also found that when irradiated with a near-infrared light LED (emission wavelength: 950 nm), it exhibits abnormal swimming behavior, such as rolling that rotates toward the lateral side around the body axis and looping that rotates toward the anterior around ventral side. It was also clarified that swimming and feeding are possible by irradiating visible light from one direction even under microgravity. In a gravity sensing experiment conducted by creating different gravity environment from micro to 0.2G by a similar aircraft experiment, it is possible to maintain their posture from about 0.1G, and under 0.2G, almost all individuals swim normally even without light irradiation.
From these results, it was possible to clarify a part of the material flow when performing material recycle aquaculture with tilapia in space, and it was suggested that tilapia show the normal swimming and is possible by fully adapting to the gravity of the moon and Mars.
In the future, it is necessary to study aquaculture technology with a view to alternation of generations, assuming long-term fish breeding.