Journal of Fisheries Engineering
Online ISSN : 2189-7131
Print ISSN : 0916-7617
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Volume 31 , Issue 1
Showing 1-8 articles out of 8 articles from the selected issue
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  • Jun HAN, Etsuyuki HAMADA, Yoshihiko NAKAMURA, Kiyotaka SAITO
    Volume 31 (1994 - 1995) Issue 1 Pages 1-6
    Released: January 01, 2018
    JOURNALS OPEN ACCESS
    Remotely Operated Vehicles (ROVs) equipped with underwater video cameras are often used to conduct Visual investigations such as observing fish behavior. It is, however, Very difficult to guide an ROV to its target Without the aid of an accuracy positioning system. Therefore, We have developed an ROV positioning system using an ultrasonic pinger, Which presents a highly accuracy real time track pIot. A pinger is an underwater ultrasonic tag, Whose bearing can be determined from the directivity of a directional transducer, and the distance from the transducer to the pinger is inferred from the amplitude of the received pulse. The positioning accuracy in such cases however, is unreliable. In this study, the distance from the transducer to the pinger is calculated by using an original method in which the receiver and the pinger are Synchronised to measure the time difference between transmitting and receiving a pulse. A synchronising drift error which accumulates with time was corrected by using the time average of the distance which was calculated from the transmission loss. In this way we obtained more accurate measurement of distance. Using the distances calculated by the synchronising method, We fixed the ROV position using the range-range (p-p) positioning method. Compared with the hyperbolic positioning method, the positioning accuracy in this study is clearly improved.
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  • Toshihiko FUJITA, Daiji KITAGAWA, Yasutoshi JIN, Yusaku OKUYAMA
    Volume 31 (1994 - 1995) Issue 1 Pages 7-13
    Released: January 01, 2018
    JOURNALS OPEN ACCESS
    A combination method of TV camera census and fishing-gear sampling was devised to estimate demersal fish abundance on artificial reefs. Capturing area (A') of a fishing gear for a fish species was defined as the area Where all individuals of the species could be captured by the gear, i.e. catchability q=1. When A'was determined, density (D) and biomass (B) can be estimated by the fishing gear, calculated from the number captured (C) and their weight (W) using the equations, D =C/A'and B= W/A'. we evaluated A' for a bottom trammel net and a bottom long line by sampling where fish densities were measured by a TV camera census. The density and biomass of the dominant fishes on Okama artificial reef situated at a depth of about 130 m off Kamaishi, Japan, Were estimated by using these two fishing gears.
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  • Masato HAMAGUCHI, Kazuyoshi UCHIDA, Shinya SHIMOKAWA, Kazuyuki MAEDA
    Volume 31 (1994 - 1995) Issue 1 Pages 15-20
    Released: January 01, 2018
    JOURNALS OPEN ACCESS
    To clarify the characteristics of NOx emission and optimum speed for environment on a small fishing boat, concentration of NOx and O2, Ship's speed and fuel oil consumption were examined by using 12 GT size fishing boat equipped with 265kW/2200 rpm 4-CyCle marine diesel engine. Two comparative examinations, Sailing and trawling conditions, were carried out in order to study the relationship between the ship's speed and NOxemission. The results obtained from the examinations are as follows : (1)At the sailing condition of a sIow speed, NOx emission [kg/h] increased proportionally to the approximate square of the ship's speed, but the condition of a high speed, the NOx emission practically keeps constant value ; (2) Both conditions of sailing and trawling, NOx emission [kg/h] correlates with fuel oil consumption ; (3) Total NOx emission [kg] per unit sailing distance increased with the ship's speed unti1 13 knot, then decreased gradually ; (4) To sail at the high speed that actual fuel oil consumption become smaller than theoretical fuel oil consumption based on propeller low is effective for reduction of NOx emission and improvement of fisherboat’s function.
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  • Fuxiang Hu, Ko MATSUDA, Yasuyuki YAMAKOSHI, Tadashi TOKAI
    Volume 31 (1994 - 1995) Issue 1 Pages 21-26
    Released: January 01, 2018
    JOURNALS OPEN ACCESS
    An accelerated motion of conical net is associated with a reduction of water velocity inside the net. Water mass retained inside the net will move with the towed net. This water mass is defined as the added mass. In order to evaluate the added mass of the conical net, ten models of different mesh factors and attack angles were tested in a large scale towing tank at the National Research Institute of Fisheries Engineering. The measured added mass is then converted into dimensionless added mass coefficient using the volume of the conical net and the mesh factor. The added mass coefficients of conical nets can thus be compared by type of models and evaluated.
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  • Hu CHEN, Sadami YADA
    Volume 31 (1994 - 1995) Issue 1 Pages 27-32
    Released: January 01, 2018
    JOURNALS OPEN ACCESS
    In this paper, an experimental system was constructed by a vacuum pump, a suction room, two sets of ball valve and sieve of longitudinal. In the system, the fry was sucked from head. In order to hold invariable suction velocity, the suction pressure of the system was adjusted by tank of pressure control. By using two sets of laser sensor set up outside wall of a measuring pipe (or U-shaped ditch), the body length of the fry inside the pipe (or U-shaped ditch) was measured when the fry drained from the system. The ability of the laser wave to pass through pectoral fins, the effects of the existence of water, diameter of the measurmg pipe and the fry velocity on the accuracy of measuring fry body length were discussed. Measuring error caused by laser wave diffusion was also analyzed. The results were as follows. 1. When fry body width (13 -18mm) was nearly equal to the imer diameter (20mm) of a measuring pipe, the measurement of fry body length was most accurate as the laser wave could pass through the pectoral fin. 2. Whether the velocity of the fry inside a pipe flowing water rose or not, measuring accuracy didn't drop. When measuring fry body length, it was necessary to adjust the velocity of the fry inside the U-shaped ditch to below 2m/s, because measuring accuracy dropped if the velocity rose to 2m/s. 3. As this system had only a minimal measuring error (0.0959mm) caused by laser wave diffusion, it could be considered an effective method for measuring fry body length.
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  • Haruyasu KIMURA, Vicham INGSRISAWANG, Michikazu BAN
    Volume 31 (1994 - 1995) Issue 1 Pages 33-40
    Released: January 01, 2018
    JOURNALS OPEN ACCESS
    Local scour plays an important role on sinking phenomena of artificial fish reefs placed on sand bed in shallow seas. If artificial fish reefs sink into sea bottom, they lose their ability to gather fishes. In order to clarify this sinking mechanism and to overcome this problem, an experimental study on local scour around an artificial fish reef was initiated. This paper presents the results of experiments on scour around cylindrical artificial fish reef models in one way currents in an open channel. The local scour around artificial fish reefs is substantially different from that of bridge pier which have been investigated by many researchers because the artificial fish reef inclines and slides into the scour hole developed in scouring process. In addition to actual scour tests, a flow visualization study was carried out to understand the flow pattems around cylindrical shape models. The important parameter for estimation of the equilibrium local scour depths around the artificial fish reefs was found to be the ratio of the sediment number (Ns) to the critical sediment number (N*sc ), when the model width to water depth ratio was constant.
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  • Haruyasu KIMURA, Masahito IZUMI
    Volume 31 (1994 - 1995) Issue 1 Pages 41-45
    Released: January 01, 2018
    JOURNALS OPEN ACCESS
    Water temperature, salinity, dissolved oxygen, nutrient salts, transparenoy and benthos were observed throughout a year in Uranouchi Bay, Kouchi Prefecture. In a stratified season, the benthos died, the concentration of nutrients increased and the environments of bay were becoming worse rapidly due to the oxygen deficincy occurred at the sea bottom.
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  • Symposium Executive Committee
    Volume 31 (1994 - 1995) Issue 1 Pages 47-56
    Released: January 01, 2018
    JOURNALS OPEN ACCESS
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