Scallop culturing by ear-hanging method demands drilling of hole in the ear groove on the left shell for which
an equipment for automatic in-line positioning and posturing of the scallop shell is required. The authors develope
such an equipment with revolving rollers, and discuss mechanical conditions for controling posture of scallop
shell. The results are summarized as follows.
The characteristic of the scallop shell's contour is that while most part of its contour is circular shape, it has
a straight line part at the ear. Under the action of the two revolving rollers, the vertically positioned scallops
start revolving between two holding plates and when the ear of scallop gets into the gap of the two rollers, it
stops rotating with the ear facing down and the ventral margin up. Thus, automatic posturing of the scallops is
made possible. When the gap S between two rollers is (0.54-0.77)L, the gap B between two holding plates is
(1.09 -1.15) W, the revolution number 71 of the rollers is from 84 to 212 rpm and the diameter of the roller is
less than 0.34L, the success rate of posturing of ears reaches 100 %. where L : length of shell, W :Width of
Theoretical formulas in the finite depth estuary were developed based on the formulas by Tamai and Arita
in the infinite and their proprieties were verified by experiments.
(1) The entrainment rate Q is related to the densimetric Froude number at the outlet of river water, the
non-dimension depth of the bay R and the supply of sea water at the mouth.
(2) Q has the critical number QR determined by R. TO increase the entrainment rate, We should increase
the outlet densimetric Froude number of river water and the supply of sea water from the mouth or the depth of
It has been suggested that aquacultural facilities should be set up in open sea areas because of decreasing
fishing grounds in calm bays. n these areas it is necessary to construct wave control structures so that aquacultural
facilities, e.g. net cages, are not carried away.
In this study wave deformations around a submerged plate as wave controI structures are estimated by solving
linearized three-dimensional wave diffraction problems using the hybrid method. In some cases, the plate size,
plate set up condition and incident wave condition are changed.
Our calculation results show that low wave height areas are fomed into belt-shapes from a side of the plate.
However, When kh≦1.0 or w/h≦1.0 (k is the wave number, h is the water depth and w is the width of the plate),
it is not expected that the wave could be controlled by the submerged plate. It is shown that the low wave height
area of H/Hi≦0.6 (H and Hi are the wave height at a calculated point and the incident wave height, respectively)
is larger when w/h≧2.0, d/h≦0.3 and the sloping angle of the plate≧30 (d is the depth of the plate).
When constructing and improving fishing ports and communities, fundamental concepts based on ecological
aspects are required to recognize the value of the ecosystem and to coexist with nature. As a first step to assess
the construction and improvement of fishing ports and communities from ecoIogical viewpoints, We conducted
the following surveys and studies. We conducted a questionnaire survey on the natural environments and the
living conditions of wildlife in fishing ports, as well as on the habitat conditions of the wildlife listed in the
category subject to assessments,in our country. The results are as follows ;
1) The fewer the artificial structures, the more diversity in the topographic features of the surrounding areas.
2) Changes in the number of wildlife were confirmed at more than half the surveyed fishing ports, which is
evidence of the ongoing trasitions of the ecosystem.
3) Drastic increases and decreases in the populations of wildlife are likely to occur as the diversities of the
nature are smalller.
4) The living conditions of the types of wildlife listed in the category subject to assessments were found.
Furthermore, the ecosystem-friendly fishing port construction and improvement method was examined to
conserve and restore the ecosystem around fishing ports.
Two field investigations were executed to study relationship between port structures and marine organisms.
The first investigation deals with the process of attachment of marine organisms (sessile animals, mobile animals
and seaweeds) on concrete blocks in the sea. The blocks having several wall properties were prepared. For example,
uneven type and sulfate of iron (FeSO4) coating type etc. Marine organisms,attached on the blocks which
were set in the sea water for about 2 years, were studied from both qualitative and quantitative points of view
related to marine ecology. The second investigation deals with the aquatic data collected by the Ministry of Transport.
Relationship among two physical factors (waves and port structure type) and the quantity and quality of
marine organisms was studied.
As breakwaters having the function of seaweed bed, sloping breakwaters with rear step and a wave absorbing
works with a small step were constructed. Also, to confirm the function of breakwaters as spawning ground, a
investigation has been made on the spawning situation of loligos at inside and out side ports. It was found that a
wave absorbing work and the like are functioning as spawning grounds in ports where the loligos are migrating.
Authors have been developing the armor block that was added the function of the loligos spawning ground and
applied them to some fishing ports in Hokkaido.
In order to clarify the function of breakwaters as habitats for fishes and shellfishes, a gill net investigation
was conducted around breakwaters and in comparative zones where there are no.structures. Quantity of fish
catch by gill net around breakwaters was greater than that in the zones.
Recently, marketing of live fishes becomes prosperous. We surveyed present conditions and problemson live
fish-stocking in fishing ports. It appears that to get worse the water is anxious. But the technique of controlling
water condition is not established yet. Authors have proposed a method of waterintake works with a submerged
mound regarding the design and layout. It was reported from field survey that the constructed facility was able
to intake seawater to a sufficient amount and it is useful for purifying the basin.
Surf clam Psendocardium sybillae living in sandy beaches along the open sea in northem Japan is important
fishery resources. It has been found that the populations of surf clam has been increasing with the extension of
the breakwater. In the case of Ishikari Bay New Port, one of the major factors of that increase is the formation
of the calmness fields of waves and the circulation fields around the port. The behavior and mortality process of
live bivalves affected by waves was experimentally studied.
Associated with the port construction and/or coastal reclamation, it is sometimes required to construct new
tidal flats or rehabilitate damaged tidal flats. Experiences on construction and rehabilitation along Japanese coasts
are reviewed. Understanding of the physical systems which support benthic ecoIogical activities is necessary. Five
elemental conditions can be pointed out for the supporting system. In the field, natural fluctuations of these
elemental conditions are inevitable. For the self-stability of the ecosystem, negative feedback mechanisms and/
or environmental gradient and variety are important for designing and management in both constructions and
rehabilitation of coastal tidal flats.