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
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.
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:
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
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 :
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.
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.
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
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.
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.
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
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.