海洋生態系工学研究室

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Innovative seafood production system

The consumption of seafood is increasing in the world. On the other hand, the production of seafood continues declining in Japan due to its inefficiency. For effective and sustainable seafood production, offshore submergible aquaculture system and automated net hauling system of set net fishery are developed to reduce the danger and labor of local workers.


Controllable Depth Cage (CDC)Submergible Cage with Flexible HosesSubmergible Cage with Improved Frame
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A cage can be installed at variable depth adjusting the buoyancy of the cage or the floats between the cage and the anchors. The vertical position of the cage can be adjusted according to the natural environment such as the attacks of high waves, algal blooming, and hypoxic water. A cage can be submerged and floated by ejecting and injecting air into the flexible hoses in the polyethylene pipes. Silver salmon was cultured at 10-20 m below sea surface in Onagawa Bay using this submergible cage, resulting in the longer time culture and adjusting shipping time. Overview of this study can be found here. A submergible cage was developed by improving the inner structure of the polyethylene pipes in order to exchange water and air efficiently. This submergible cage can be made by improving the generally prevaililng cages. Field test was carried out near Kashiwa-jima in Kochi Prefecture for tuna farming. Overview of this study can be found here.
Feeding Barge for Offshore AquacultureAutomated Net-hauling System
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A barge ship was developed to feed fish in the submerged cages in an exposed sea. A barge escapes when the significant wave height is more than 4 m, whereas the feeding period can be extended by 40-50 days. The field test was carried out in Shibushi Bay. An automated net-hauling system is developed for human-saving and labor-saving of set net fishery. The hose net that is made by connecting flexible hoses is floated gradually by injecting air in order to corner the fish in the box chamber net for harvesting.

Environmental impact assessment and ecosystem simulation for lakes and coastal seas

A wide variety of environmental problems arises in the world lakes and coastal area. A hydrodynamic and ecosystem coupled model is developed to understand the physical, chemical, and biological processes in aquatic environment. The effects of eutrophication and climate change on the ecosystem are examined for Tokyo Bay, Lake Biwa, Lake Kasumigaura, the Caspian Sea, aquaculture pond, etc. Then the measures to these problems are propopsed and their effects are predicted by numerical simulation.


Collision Risk to TurbinesCarrying Capacity of AquacultureCollaboration with Fishery
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Environmental impact assessment is required for installation of marine renewable energy facilities. The collision of marine animals to turbine blades is worried. The collision risk is examined by water tank testing. The effects of turbine blades on the physical environment are also predicted by numerical simulation. We join Annex IV (Environmental effects) of Ocean Energy Systems in International Energy Agency. Overview of the water tank testing of the collision risk can be found here. Self-pollution problems caused by algal blooming and hypoxic water occur at the aquaculture site in the semi-closed bay. Numerical simulation of material cycle in the aquaculture site is carried out in order to predict its carrying capacity. Integrated Multi-Trophic Aquaculture (IMTA) is also considered as a countermeasure of the self-pollution problems. Overview of this study can be found here. The use of sea area should be permitted when marine renewable energy facilities are installed. The change in the distribution of marine animals caused by installation of devices should be assessed in collaboration with fishermen. The observation system using circular fish-eye cameras is developed to observe marine animals around devices. Overview of this study can be found here.
Oxygen InjectionReverse SimulationToxin Simulation
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The effects of hypoxic waters on bivalves are the serious problem in Ariake Bay. The method of injecting oxygen into hypoxic water on the bottom is developed. This new method is cheap and used easily by fishermen. The bivalves in the hypoxic water can breathe temporally. The source of pollusion should be specified as soon as possible if any pollution is detected in waters. The governing equations are solved inversely in time in the reverse simulation. The performance of the reverse simulation was verified by vertual pollution problem in Lake Biwa. Overview of this study can be found here. The transition of algao species occur and toxic algae appear in Lake Kasumigaura. Toxin modeling is combined with the hydrodynamic and ecosystem coupled model in order to reveal the reasons of algal species transition and toxic algae appearance in Lake Kitaura.
Regeneration of Heda BeachCaspian SeaLake Ikeda
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Lots of species of bivalves existed in the beach of Heda in 1960s, whereas the number and species of bivalves decreased rapidly due to intorusion of sludge and construction of breakwaters. The purpose of this study is to regenerate the rich ecosystem in the beach of Heda. The overview of this study can be found at this site. The development of oil and gas resources becomes active around the Caspian Sea. The prediction of oil transport is required when the oil spill occurrs in the Caspian Sea. Numerical simulation was carried out to reproduce the physical environment in the Caspian Sea. The overview of this study can be found here. The overturn sometives ceases in Lake Ikeda probably caused by climate change. Numerical simulation is carried out in order to predict the physical environment and water quality in Lake Ikeda.
Lake BiwaModeling Sessile OrganismsEIA of Floating Platform
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Insufficient overturn caused by climate change is worried in Lake Biwa. According to the future senarios of climate change, the future environment is predicted by the hydrodynamic and ecosystem coupled model. Then the results of numerical simulation will be applied to environmental risk finance. Marine organisms settle in several layers on artifical substrate. Active and inactive organisms should be discriminated in order to predict the effects of sessile organisms on the surrounding water quality. A competition model for space and food was developed for mussels. The overview of this study can be found here. A very large floating structure (called Mega-Float) will be used for offshore city and runaway. The environmental impacts of the Mega-Float should be assessed in advance. The hydrodynamic and ecosystem coupled model was developed to predict the effects of Mega-Float on the surrounding environment. The overview of this study can be found here.

Marine renewable energy

The development of marine renewable energy is active all over the world. Focusing on the wave energy, the efficiency of converter is improved and its application to the fishery or the other sectors are discussed.


WHzerLinear WEC and OETR
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Motion-controlled small ship with wave energy harvester is developed. The performance of the experimental ship with the length of 3.3 m was examined in Yuya Bay and off Hiratsuka. The overview of this study can be found at this site. OETR (Ocean Energy for Tohoku Regeneration) research group studies on the linear-type wave energy converter in order to test the device in the demonstration field of ocean eneryg off Kamaishi, Iwate Prefecture. For the OETR group, please visit this site.

Aquatic environment preservation by an electrochemical method

An electrochemical method is expected to be one of the preservation methods of aquatic environment. The electrolysis produce hydrogen and oxygen, which are supplied for energy use and for hypoxic or annoxic water, respectively. It can degrade inorganic nitrogen which causes eutrophication in lakes and coastal seas. Charcoal enclosed and dielectric electrodes are developed to suppress the consumption of these electrodes.


Charcoal-enclosed ElectrodeDielectric ElectrodeAnti-fouling to Nets
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Charcoal-enclosed electrode is developed to suppress the degradation of the electrode. The performance of decomposing ammonium is examined by the electrolysis using charcoal-enclosed elecerodes. Dielectric electrode is developed to suppress the degradation of the electrode. The electric current flows if the polarity is changed. The performance of decomposing ammonium is examined by the electrolysis using dielectric elecerodes. Titunium is inserted in the twine of the fishing net. A very small quantity of hypochlorous acid is produced by electrolysis in order to prevent the settlement of sessile organims to fishing nets.
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