A pelagic and/or midwater trawl using flexible canvas kites as a net-mouth opening device was developed for conducting fishery resource surveys. Wing kites to replace the otter board, and para-kites to replace the floats and sinkers, were designed. During sea trials, a constant net-mouth opening was obtained. The trials clearly show that the kite trawl designed in the present study is able to provide a high-quality net-mouth opening, and that the stability of the trawl is satisfactory under various towing conditions. Moreover, the validity of both the design method and the model testing method for the kite trawl were verified in the context of the trawl' s suitability as sampling gear for fishery resource surveys. In the future, this technology is expected to spread to commercial fishing sites.

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Flow field in rearing tank is generated by aerators, however, few studies evaluating such flow field in detail had been conducted. In the present study, we attempted to clarify the relationship between the flow pattern and the topological character on a vertical cross section through the flow. The effect of aeration rate and aspect ratio (the ratio of water depth to tank radius) on overall flow pattern was investigated experimentally, by use of flow visualization techniques. The results showed that flow patterns were classified into 2 cases, namely 1 vortex pair and 2 vortex pairs systems, as the value of aspect ratio varies almost 1.0 to 2.0, respectively. On the other hand, the change of aeration rate weakly affected these change of vortex pair systems. In addition, corner vortex structures were observed in the both region between the free surface and the upper side wall, and between the bottom wall and the lower side wall. On the side wall, reattachment and separation points were found, which were closely related with these vortex structures.

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The influence of hypoxic water on the early growth rate of the ark shell Scapharca kagoshimensis was examined at six stations, representing different hypoxic environments, in Mikawa Bay. New recruits of S. kagoshimensis appeared from late August to early October at each station. However, the growth rates thereafter differed among the stations; the maximum difference in growth rates among stations was fivefold. The growth rates were closely related to dissolved-oxygen saturation, so it is probable that hypoxic water strongly reduces the early growth rate of S. kagoshimensis in Mikawa Bay.

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We investigated schooling behaviour and the rheotactic reaction in the dwarf sweetfish Plecoglossus altivelis. Under 400lx illumination, the fish formed schools with low polarity; these aggregations were highly compact. There was no schooling behaviour in darkness (0.01lx). A positive rheotactic reaction occurred at current velocities >3.3cm s^<-1>. At current speeds &ge;5.2cm s^<-1>, fish ground speeds declined to zero. There was no clear rheotaxis at current speeds <3.3cm s^<-1>. These results suggested that the stimuli by these slow currents might be too weak to increase the rheotaxis of P. altivelis. Current speed was thus an important factor affecting swimming effort and direction in P. altivelis. Current effects may be particularly strong in dwarf sweetfish because the schools have low polarity.

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Two methods of the cooling water surface convection, namely Kimura's One-Dimensional Convection Method and Energy Method, are investigated to reveal the thermal structure in the boundary layer and to estimate the surface water falling flux. The methods are applied to the vertical water temperature distribution data at the lake KAGAMI DAM in Kochi Prefecture, Japan from December 9, 2003 to January 20, 2004. The conclusion is as follows: (1) Thermal convection cooling water surface occurs only when the surface water temperature is higher than 4℃. If water surface cooling thermal flux is the same, regardless of the water depth, the higher the surface water temperature is the more actively convective movement occurs. (2) Cooling thermal energy flux added to the unit area of water surface Q_o during the observation period at the lake KAGAMI DAM was revealed to be from 80 to 320 (Js^<-1>m^<-2>). (3) Surface-cooled sinking flow flux q_b has come out to be from 1×10^<-5> to 5×10^<-5>ms^<-1>, i.e. the transported water from the surface to the deeper layer amounts from 100 to 180 liters h^<-1>m^<-2>, which entrains oxygen from the water surface to the deeper layers. (4) Velocity (u_λ) of the maximum vortex scale which corresponds to the mean depth of the lake (30m) are from 22 to 47mh^<-1>, which means surface-cooled sinking water reaches the lake bottom around from 40 to 80 minutes.

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A contra-rotating propeller (CRP) system was installed on the purse seiner Nippon Maru in 2006. This system utilizes two propellers that operate in tandem while rotating in opposite directions from each other. The front propeller is driven by the main diesel engine while the rear propeller, which is installed on the rudder, is driven by an electric motor. This system is expected to produce improvements in propulsion efficiency over conventional propulsion systems consisting of one main engine and a single propeller. In this study, experiments aimed at measuring fuel consumption of the Nippon Maru were conducted to evaluate the fuel-conservation effects resulting from variations in front and rear propeller speeds. The results showed that the fuel consumption under CRP operation was 15% less than that experienced during same speed operation of the vessel using the front propeller alone. Furthermore, it was found that the fuel consumption of Nippon Maru using the CRP system was lower than that of a similar conventional purse seiner with a single engine/propeller system at medium speeds of between 11 and 15 knots, although no such decrease was seen at high speeds. In the future, an integrated control system for controlling both propellers using a single throttle control lever should be developed.

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Based upon the understanding of niche (raison) of "fisheries engineering" such as engineering researches and technology developments for sustainable utilization of fisheries resources by human being, the following 3 selected subjects were described as the importance and current our understanding; (1) possible increase of fisheries resources by ocean fertilization, (2) complete aquaculture of fish eating fish in offshore using least fish powder and fish oil, and (3) restoration of coastal marine environment in order to recover sustainable supply of natural fisheries resources.

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Conventionally, the primary objective of the construction of fishing grounds has been to create a habitat environment of the specific species for fishery, where main purpose is often to directly grow aquatic organisms that occupy an upper trophic level. However, this method might provide a possibility to destabilize the interactions between organisms including the interspecific competition and the predator-prey relationship, as well as to result in unexpected resource changes or the extinction of some species. To avert such risks while maintaining and growing fishery resources, it is effective to facilitate the species whose trophic level or ecological niche is lower than that of the target species. Thus, future efforts should be shifted to creating this type of environmental productivity. A future development of fishing grounds should focus on the promotion of the material circulation which occurs in an extensive sea area and driven by the life cycle of aquatic organisms, and the development of a cleaner and more productive aquatic environment. This would be accomplished by improving the quality and efficiency of aquatic organisms' life cycles, while reproducing and creating the environmental infrastructure that closely relates to the early stage of growth of aquatic life, such as seaweed beds and mud flats.In order to accurately evaluate the results of the development of fishing grounds that are characterized by high uncertainty and variability, it is necessary to build and use a fishing ground developing process that is adaptive and based on the PDCA cycle which is regulated by the generation time of the target species and the time before the effect reaches. To maintain the PDCA cycle, it is required to prepare an implementation plan that incorporates collaboration with various entities if necessary. In this respect, it is urgently needed to develop a tool or procedure to reach agreement among such entities, as well as build a process that allows such entities to reproduce extensive fishing grounds safely, easily and for low cost.

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The study of an artificial reef consists of three fields; 1) Fisheries civil engineering field of artificial reef of structure, stability, etc. 2) Biological field of artificial reef and fishes' ecology etc. 3) Society and economics field of effect of fishery production by artificial reef etc. In this paper, the progress, state and development of study of an artificial reef is described from three fields.

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Aging of fishing boats has been serious problem on the sustainment and reorganization of fishery with fishing boats because of prolonged wrong condition without renewal of fishing boats. Finally, the renewal of aged fishing boats gets underway by the policy of the fisheries agency from 2007. These measures are aiming at the rebuilding of the production system in the offshore/pelagic fisheries. On the potential problem about the seakeeing qualities and labor environment on the Japanese fishing boats, it is well known that regulation of gross tonnage has been strong restriction for various improvements of fishing boats. Further, it is suggested that the resource management by gross tonnage and allowed number of fishing boats has no rationality. Then, considering future fishing boat and fishing production system, we need special freedom to design. It is a good opportunity now because built fishing boats will be used in future.

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