Animal and plant communities in Saｒgassum beds were compared among some areas with different vegetation to analyze environmental conditions, which may determine compositions of communities. Study areas were natural Sargassttm vegetation area and some artificial Sargassttm beds on the concrete blocks ; poly-species area which was disturbed partly, S. giganteifolinm area on which all macrophytes except for S. giganteifolium were removed and barren area on which all organisms were removed. These areas were useful to study the influences of macrophyte on community structure in Sargassum beds. In the phytal animal communities, arthropoda especially gammaridea and caprellidea were dominant, and bivalves in animal communities on the bottoms. Biomass of phytal animals seemed to be related to size, density and species diversity of macrophyte. Then it was thought that habitat complexity and biomass of microphyte as food were very important for phytal animals. On the bottoms, animal densities were probably determined by the area of bared bottom suited for settlement. We could further compare among some Sargassum beds in different phases of succession. It enables to study community succession in Sargassum beds.

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Trapping drift algae can be a useful engineering technique of enhancing habitats for commercially important abalone and sea urchins because most of food algae may be swept out of their nearshore habitats by waves. However, many attempts with artificial barriers made primarily of concrete blocks and quarry rock have failed to trap drift algae because drift algae can be easily raised over barriers by turbulent water flows caused around them. This paper describes a mathematical method of predicting the wave-induced velocity at which drift algae begin to pass over the block under waves. A scale-model experiment in a wave channel shows that the dimensionless velocity limit, defined as the ratio of the velocity amplitude limit to the fall velocity of drift algae, increases with the ratio of the block height to wavelength. A good agreement was found between velocity amplitude limit predicted from the empirical equation and that observed in a field experiment.

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太陽電池の漁船への応用を前提とした高効率運転の確立を目的として,太陽電池の高効率運転が得られる売電圧制御に,素子温度により設定電圧を調整する機能を追加した太陽光発電システムの実験を実施した。その結果,変換効率は前報で得られた効率を2ポイント上回り15%を確認した。また,本装置を実船に搭載した場合の発生電力を推定し,一日当たり約67kWhの電力を得た。これは,蓄電池系統の浮動充電装置の電源として利用可能なことを明らかにした。

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For scallop Patinopecten yessoensis, fom factors (e.g., shell height, projection area, submerged weight and volume) were measured. So they can be expressed as a function of the shell height. Drag, lift and mass force acting on scallop were measured. And drag coefficient, lift coefficient and mass coefficient were calculated. Most great force act on scallop when current flow towards scallop at a 0 degree of attack angle and 15 degrees of inclined angle. The critical flow conditions of the initial movement can be determined based on the balance condition of the rolling moment. The wave conditions that fomed the habitat were also detemined by small amplitude wave theory. The allowable significant wave height (H1/3) can be expressed as a function of the period (T), the wavelength (L), the depth (h) and the shell height (SH) in the following formula:

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Automatic ear-hanging machines have been developed recently in order to reduce amount of manual labor in scallop aquaculture. This paper present theoretical and numerical analysis of conditions for production cost reduction. Operating inferiority concept of MAPI (Machinery and Allied Products Institute) was used in calculation model of the production cost calculation. Then, required minimum throughput qmin (g) and operation time rtmin, (g) was presented as functions of amual inferiority gradient g. Numerical analysis allowed finding out the following figures : 1. Estimates of the upper and lower values of amual inferiority gradient, gmax and gmin. 2. Mechanization is effective when amual inferiority gradient of the machine meets the condition :

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In this paper, attention is focused on how physical environmental conditions, such as water temperature and tide affect on the Sepia esculenta catch in the fishing grounds of Ariake Sound. In a project done to collect basic data on variations in S. esculenta catch, the comparative studies were made using catch data obtained in different fishing grounds. The data used in evaluation were the catch by cuttlefish basket traps in 1996 fishing period (15 February-15 May ; off Fukae town, and 5 January-13 May ; off Ariake town). The water temperature in each fishing ground was recorded continuously for 20 min with the aid of a thermistor attached on a basket trap. Daily mean tide range in each area was calculated using tide table. Catches were high at water temperature between 12-14 degree. Daily catches varied periodically due to the change in the lunar cycle, and it became maximum at neap tide, or ebb, and minimum at spring tide. In this region, Water temperature seems to be an important long-term factor affecting the main fishing period, and tidal current seems to be an important short-term factor controlling daily catch. The results suggested that the amount of catch was controlled by both water temperature and tidal current, which is therefore the important factors in the S. esculenta basket trap fishery.

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DGPSは補正データを伝送することによって利用者側の測位精度を向上させることができる。この補正データの伝送に遅延が生じれば,利用者側のDGPSによる測位精度は劣化する。そこで,利用者側の受信機を補正データを送信する側のすぐ近くに置いた場合と,約210km離れたところに置いた場合において,補正データの伝送遅延時間が及ぼす測位精度の劣化程度がどのようになるかを解析した。その結果,送信側から210kmのエリア内の測位誤差は,補正データの伝送遅延時間と利用者側のDGPSの測位誤差にのみ影響を受け,送信側から利用者までの距離の影響は受けないことが分かった。このことにより,補正デ=タ伝送遅延時間による測位誤差を簡単に求めることが出来る近似式を導き出した。

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In this study, discussed the method to simulate the bottom environment of sublittoral muddy bottom under the breeding, which use for culture of fauna in muddy bottom. In the case of same density but diffferent grain size of substram, showed that same moisture content approximately in each grain size at larger quantity of seawater, although showed that high moisture content in coarser grain size at smaller quantity seawater like in aquaria. In the case of different specific gravity of muddy substram, showed that high water content in each quantity of seawater at lower specific gravity. But muddy substram in low specific gravity couldn't hold against the decrease of moisture content with consolidation. These facts suggested that factors of substram to simulate the muddy bottom environment for the aquaria were as follows : lower specific gravity of substram, coarser grain size of substram and form of substram, since kept high level on porosity and avoided the effect of consolidation.

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A new material with high content of fly ash named 'Ashcrete' has been developed. To examine the applicability of Ashcrete to marine structures, strength characteristics, resistance to sea water attack, and safety in the marine environment have been studied. And a new manufacturing process has been developed which fluidizing fly ash, cement, admixture and a minimal amount of water mixture by series of vibrations named 'Super fluidizing method'. There are at least following four advantages in the super fluidizing method for Ashcrete production ; (1) increased quality of Ashcrete with homogeneous mixing and least cracking after drying, (2) increased economical efficiency by cutting the amount of cement by 2/3, (3) increased easy handling during operation with minimum adhesion and easy transport, and (4) increased easy mixing design with easy control of water and vibration. As the result of long term studies and underwater observations, the Japanese Govemment has approved the durability of the material, safety in the marine environment and attractiveness to fishes. It is therefore proposed that Ashcrete can be used in constructing large-scale sea mounts named 'Super Ridge' in deep water for the purposes of generating upwelling stream. The project was launched in which Ashcrete blocks were piled onto the seabed to construct a mound-shaped structure. This project is being carried out at a cost of approximately 10 million dollars spaming a period of six years.

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It is demanded to develop the durable and reasonable fence to obstacle the movement of sea urchins, because of releasing intensively and breeding sea urchins in calm sea area In present study, we made an experiment to develop the fence which can obstruct those escaping effectively, and investigate the efficiency of the fence which has the air-pocket. It was found that sea urchins did not wholly expose themselves in the air, and also they did not expose their tube feet which can cling substrates. Both northem sea urchins and shortspined sea urchins twenty-five were put in the air-pocket fence, and stood for 72 hours. As the experiment result, there was no sea urchin escaping over the air-pocket fence at all.

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The relationship between distribution of juvenile Japanese surf clam Spisula sachaliensis and environmental factors in the neighboring area of nuclear power plant was investigated. Then a life cycle model of population dynamics incorporating the environmental factors was developed to evaluate the impact of the coastal structure installation on the stock of the surf clam. And a wave transport model was also developed to evaluate the effect of wave transport on the juvenile clam. Results of juvenile surveys show that the density of juvenile clam is higher around the breakwater. The mortality of the surf clam in shallow bottom and deeper offshore areas was affected by waves and the silt content respectively. Therefore a method was developed to estimate the mortality coefficient in terms of the Shields number. The life cycle model focuses on effect of the environmental factors such as current, silt content, Shields number and water temperature on survival and growth of the surf clam at various life stages. Results of the model show that the installation of coastal structures has an effect to reduce the mortality rate of juvenile clam, so that stock abundance of the clam increased accordingly. A wave transport model for the juvenile clam shows that clams tend to accumulate in the depth zone of 8 to 10 m under average wave condition. It suggests that optimal habitats of the surf clam result from the small mortality and effect of wave transport.

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