In order to clarify the towing perfomance of jigs for oval squid, Sepioteuthis lessoniana, two handmade
sample of jigs were used in a flume tank. They are fish and shrimp types with the same volumes and different lead
weights were attached to their bodies to change the specific gravity and the position of the gravitational center.
The towing performance of jigs were recorded on video tape. The data were investigated at 0.1 second intervals,
and the speed and attack angle of the jigs were analyzed.
The hydrodynamical resistance of the fish type was larger than that ofthe shrimp type. The shrimp type has
larger attack angle than the fish type at the given speed's conditions.
Experiment on maintenance of temperature difference between of inlet and outlet cooling water in
condenser was conducted to evaluate electric power consumption of the variable speed pump used inverter
for refigerator oh the tuna long line fishing boat.
The results showed that the temperature difference of inlet and outlet cooling water in condenser was kept
Within 1℃, although sea water temperature under operation changed with the range from 10 to 30 ℃. In this
case, the system could save 6.8 kW in electric power consumption, the rate of energy saving indicated 86 %.
An emergency stop system of main engine on fishing boats operated by one man was devised to save a
fisherman who fell into the sea. This system consists of the three parts ; a transmitter, a FM radio, and a
detector. Experiments were conducted to evaluate the characteristics of the emergency stop system.
The results showed that the average of the operating distance limits of transmitter, the stopping distance
and time on the initial speed of 6.3 kt were 22.8 m, 198 m, and 166 sec, respectively. Thus this system is
expected to be significantly effective as a life-saving device for many fishing boats.
In this paper, based on the field observation, the characteristics of stratified flow and that of intemal tide
in Gokasho Bay were investigated. Observation period was from 16 June to 1 July '93. Current meters with
temperature sensor were moored at three or two layers at fourteen points, three of those were out of the bay,
two were near the mouth and nine were in the bay. Sampling interval was ten minutes.
Intemal tides were apparently observed around the bay. The amplitude of the intemal tide was decreased
toward the inner part of the bay, that is ten and some meters near the mouth of the bay, some meters near the
central part and very small at the innermost part. It is concluded that the intemal tide has an important effect
on the environment of the bay except the innermost part of it.
The information of ship waves generated by a small boat is very important to prevent damage of the floating
marine structure such as the cage for fishing aqua-culture. This paper deals with the measurements of ship waves
generated by three kinds of actual small boats, a displacement boat, a high-speed boat and a planing boat. The
main purpose of this study is to investigate the fundamental characteristics of waves generated by a small boat
passing near the marine structures. The measurements of ship waves are carried out in the cases of varying
distance from the sailing line with constant ship speed and varying ship speed with constant distance from the
The measured ship waves are compared with ones calculated by two kinds of simplified estimation methods
and the evaluations of these methods are also investigated. As results, the both calculated results show relatively
good agreement with the measured ones of a displacement boat and a high-speed boat, but have discrepancy with
ones of a planing boat.
For the purpose of development of steel fish reef, a teｓt reef was installed off the shore at Katsuura-cho,
Nachi, Wakayama prefecture in 1982. Stability and durability of the structure and swaming effect of the fish
reef have been checked with eleven diving works. Specially, for the purpose of researching the steel corrosion
amount above the water depth of about 50m, several test pieces were installed, and have been checked for a stated
period. The reef has shown the satisfying function and has been in sufficient condition in stability and durability
for these eleven years since its installment.