Shigeaki Shiotani

Improvement of the survival in the seven-band grouper Epinephelus septemfasciatus larvae by optimizing aeration and water inlet in the mass-scale rearing tank

The water flow in larval rearing tanks has been indicated to cause mass mortality of the seven-band grouper Epinephelus septemfasciatus larvae. Therefore, a new aerating method was tested in an actual scale intensive rearing tank (8.0 m in diameter, 1.87 m of water depth, 100 m3 of volume), in which an aerator was positioned at the center of the rearing tank surrounding cylindrical drain (1.2 m in diameter) to generate the flow field, and seven larval rearing trials were performed. The survival rate with the former aeration methods were compared, in which several aerators were located in the rearing tank. The survival rate at 10 days after hatching with the new aeration method (61.5±5.1%, n=7) was approximately three times higher than the former methods (21.2±13.7%, n=6). The flow environment of rearing tanks was also examined by quantifying the flow field, and the relationship between the flow field in the rearing tank, behavior of larvae and survival discussed. It was confirmed that the vertical circulating flow was observed in rearing tanks, and determined effectively the survival and the behavior of grouper larvae in patchiness.

Larval rearing without aeration: a case study of the seven-band grouper Epinephelus septemfasciatus using a wave maker

Generally, the flow field in a rearing tank for seedling production is generated by aerators to prevent stratification, to insure oxygenation and to disperse live and artificial foods. However, the bubbles hitting larvae might stun or injure them, and strong aeration might keep larvae from feeding, make them struggle and waste energy, which is lethal to the larvae. Howell et al. pointed out that oscillating horizontal paddles or vertical plungers can be used for creating the water field in a rearing tank instead of aeration. There have been studies on the effect of turbulence using the vertical plungers on the survival and feeding activity of fish larvae. However, little attention has been paid to compare the effect of the flow field generated by aeration and other flow generating methods in rearing tanks on larval survival and growth. Therefore, the present study compared the larval survival and growth between two different generating methods for flow field in the larval rearing tank; one is aeration and the other is a wave maker which creates a constant wave on the freewater surface in the rearing tank. The seven-band grouper Epinephelus septemfasciatus was chosen as an experimental fish in this study. Although E. septemfasciatus is expected as a new candidate species for aquaculture and stock enhancement in Japan, physical stress such as strong flow and light intensity, causes the water surface tension-related death, which is critical in the early phase (fromhatch to abound 10 days after hatching) of the seedling production of this species. Oil-film forming is commonly used in order to prevent the surface tension-related death in the seven-band grouper larviculture. However, surface films will not only reduces gaseous exchange across the air–water interface, but also prevent the larvae swallowing the air that is essential to normal swim bladder inflation. In the present study, the authors hypothesized that continuous movement of the free-water surface, by creating small wave, would reduce the surface tensionrelateddeathof the seven-bandgrouper larvae, and conducted a larval rearing trial for 3 weeks in order to compare early survival and growth in this species reared by the wave maker and aeration.

Simulation of Weather and Ocean for Numerical Ship Navigation

For safe navigation, high-resolution information on wind and waves is very important. In coastal areas in particular, the weather and ocean situation changes dramatically in time and place according to the effects of geography and water depth. In this paper, high resolution wave data are generated using SWAN [1][2] as a numerical wave model. To estimate waves, wind data is necessary. By using the mesoscale meteorological model of WRF-ARW, detailed wind data was generated. We simulated wind and ocean waves for the duration of a typhoon passing over Japan in September of 2004. Secondly, we simulated ship maneuvering using simulated wind and wave data. For the ship maneuvering model, the MMG (Mathematic Modeling Group) was used. Combining high-resolution wind and wave data with the numerical navigation model, we studied the effects of wind and waves on a ship’s maneuvering. Comparing the simulated rhumb lines of a ship with the dead reckoning tracks, it was recognized that the effects of the wind and waves on a moving ship were significant.Copyright

Development of radar simulator software using AIS data for ship data

A radar simulator for ships is a device for effective education concerning safety in ship navigation. In existing radar simulators, it is necessary to simulate surrounding ship data, and much effort is required to input such data. Therefore, this study aims to address this problem using AIS (Automatic Identification System) data. The proposed radar simulator system simultaneously achieves the following functions: (1) the creation and display of simulated radar images based on AIS data and (2) the display and overlay of AIS information on radar screens. As a result, it is possible to train individuals in ship maneuvering using actual ship traffic of a specific ocean area as the environment in the surroundings of ones own ship. Moreover, this proposed radar simulator system works on a general PC. Thus, it is possible to have two or more people simultaneously participate in training using a network with two or more PCs. In this paper, the outline of the proposed system and simulation results are described.

Study on the estimation of tsunami propagation from an analysis of sailing ship motion

The Great East Japan Earthquake occurred on March 11, 2011, in the coastal sea area of northeastern Japan. The epicenter was located close to the seashore. The big tsunami that was generated caused extensive damage. Over the entire Pacific coastal region, tsunami warnings and tsunami advisories were issued continuously. The short arrival time of the tsunami and late evacuation are thought to explain the extensive damage suffered. If early forecasting of tsunami propagation becomes possible, it is believed that tsunami damage will be reduced and safety from tsunamis can be ensured. This paper deals with a method of early forecasting of tsunami propagation. The AIS data obtained from many sailing ships were used and analyzed for estimating tsunami propagation. It was confirmed that this method was very original and effective.

Small Craft Assistant Information System Based on GPS and Google Earth in Real Time

The system is aimed at establishing the information support system for small craft operators. This system can also be used for playback and simulation purpose. The combination of 3D map service of Google earth and GPS can supply real time position and 3D geographic virtual circumstance. In this study, authors make the small craft assistant information system based on Microsoft.Net technology, GPS and Google Earth.Copyright

Current Situation and Difficulty of Wave Forecast From Viewpoint of Ship Management

Numerical forecasts of weather and oceanography are increasingly common in the field of ship operations due to advances in computer science. However, in some situations, the accuracy of forecasts is too unreliable to ensure safe operations. In the current study, a nationwide questionnaire is used to determine the effectiveness of wave forecasts in enhancing navigation safety. Data analysis is also shown for two cases of failed forecasts in low-pressure weather systems near Japan in the winter. Finally, recommendations are made for improving wave forecasts from the viewpoint of ship operations.Copyright

Information System for Achieving Navigational Safety by Obtaining Visual Information Using a 360° Camera

This research was aimed at building a new navigational information support system that could be used for preventing accidents involving sea-going vessels. This paper proposes a methodology for obtaining visual information with a 360° camera, this information can be used to issue early warnings. This methodology involves superimposing image groups captured with the camera, with the superimposed images also providing positional information about the locations where the images were captured. These image groups are superimposed on a map by using a geographical information system. This method is extremely effective as it enables ship navigators to acquire effective information through the visualization of surrounding conditions, particularly in critical marine areas, in addition to providing regularly used information such as that obtained from nautical charts. Furthermore, the use of this system as a navigational simulator during sea voyages is expected to reduce uncertainties for first-time ship navigators visiting unfamiliar marine regions. Therefore, the system can help prevent marine accidents.

Study on Presentation of Navigational Information of Atmospheric and Ocean in Voyage Simulation for Safety of a Ship Sailing in Coastal Sea Area

Navigational information highly affects the transporting industry. Prevention of a marine disaster is one of the best ways to ensure the safety of sailing ships. Collision and stranding are the two most common causes of marine disasters. Most coastal stranding is attributed to shallow waters. Accurate information on water depth for the prevention of ships stranding. On the other hand, information about the atmosphere and the oceans is also important. In this paper, we propose an effective method to communicate information regarding water depth, the atmosphere, and the oceans using Geographic Information System (GIS) to prevent ship stranding.

Numerical Simulation of Tidal Current or Wind Over the Sea and Applications to Navigational Simulation of a Sailing Ship

This paper deals with numerical estimations of the ocean surface wind and tidal currents in a bay. Such estimates are very important because the wind and tidal current react to environmental factors, such as the effects of a marine structure or a sailing ship. The final object of this research was to develop a weather routing system for small vessels in coastal water. First, a computer simulation of tidal current was carried out in the same bay in Japan. The results showed that tidal simulation was very effective for the weather routing system of a small vessel. Next, an estimation of the ocean surface wind was carried out in Osaka Bay using the MM5 mesoscale meteorological model. A comparison of the calculated numerical results with the observed ones was confirmed that the ocean surface wind in Osaka Bay was accurately estimated. Third, as an application of the estimation of wind or tidal current in the bay, navigational simulations of a sailing ship under the effects of the wind or tidal current were conducted using the numerical data of the ocean surface wind or tidal current separately. The importance of this simulation method for ship positioning was confirmed, as was the accurate estimation of the effects of wind or tidal current in coastal water on a sailing ship in a navigational simulation for optimum weather routing.Copyright