In ocean areas where the shortage of spores was a factor limiting growth, large quantities of one-year old brown macroalgae (Ecklonia cava) cultivated on artificial substrates were transplanted in large quantities to submerged breakwater to form beds. In November 1994 and January 1996, approximately 12,000 and 15,000 brown algae samples were transplanted to the site. After six years in March 2001, the area of the beds reached its maximum area of 8,000m^2, implying that the beds expanded at a rate of 20〜48m/year. In low temperature years, the attachment of large numbers of juvenile brown algae was the trigger for bed expansion. During the years when the beds were expanding (1994-2001) there was little feeding pressure from herbivorous animals. Although the submerged breakwaters along the Seisho Coast were originally intended as wave suppression features, they were very effective for creating seaweed beds and for protecting and nurturing marine organisms. In fact, it has been suggested that these breakwaters contributed to an increase in coastal fishery production. Unanticipated factors that contributed to limiting the growth of the beds included strong waves (Autumn 2001), which washed away sections of the brown algae beds, and also heavy grazing by herbivorous fish (Siganus fuscescens) (Autumn 2004). The localized algae beds that escaped grazing occurred in areas where the waves and currents created habitats with complex flow conditions. In addition, access to these areas was limited and they were characterized as having strong circular flow and near shore currents. While grazing by S. fuscescens resulted in the loss of approximately 80% of the brown algae beds, there has been considerable recovery of the brown algae beds since 2006. Long-term monitoring will be continued in the future to increase our understanding of the factors responsible for changes in the distribution patterns of brown algae beds established on submerged breakwaters.
Trolling fishery is a typical fishing method used for catching fish that swim at high speeds, such as tuna, skipjack, and yellowtail, in tropical and subtropical regions. The structure of fishing gear is quite simple and consists of a rod, main line, trolling depressor, leader line and lure. The trolling depressor can be used to submerge the lure when it is being towed. The movement of the trolling depressor is important for catching the target species. The purpose of this study is to clarify the movement of a trolling depressor. The experiments were conducted using a flume tank to clarify the characteristic movement of the trolling depressor. A 3-component load cell measured the line tension. The displacement of the point where the line was connected to the trolling depressor was estimated by the line tension. The period of the y component's displacement was twice as long as those of the x and z component's displacement. It was clarified that the locus of the point was similar to number "8" on the xy, yz, and xz planes. A flume tank experiment was conducted to measure the tension of the line and the attitude and angular velocities of the trolling depressor. In this experiment, a 2 times larger model of the trolling depressor was used to install the underwater motion measuring unit. The acceleration, attitude and angular velocities of the trolling depressor were measured using this unit. This experiment enabled to clarify the change in pitching angle, rolling angle and yawing angle of the trolling depressor, and each period was 0.7, 1.4, and 1.4 seconds.
Flume tank experiments were performed to examine the fluid characteristics of the towing buoy in which the transmitter was installed to track movement of whale shark. The improved-type buoy is made of syntactic foam with high pressure-tightness and buoyancy, and has a streamline shape with the dimension of 48cm long in total, 4cm and 6cm in maximum width and height, compared with the conventional buoy of 39cm long and 12cm in maximum width. The towing drag, lateral force, lifting force, and pitching moment of their buoys were measured with a six-component balance at attack angles ranging from -30°to 30°, and at current speeds ranging from 40 to 140cm/s. Coefficient of each force, moment, and pressure center were also obtained. The drag coefficient of the improved-type buoy was below 0.1 within the attack angle range between ±10°, which is smaller than that of the conventional type at any attack angle. Coefficient of pitching moment of improved-type buoy within the attack angle range between ±10° was quite small, and larger than that of the conventional type. The conventional buoy has its pressure center in the anterior of the body, which causes unstable posture in towing. In contrast, the improved-type buoy has a pressure center in the posterior. Therefore, its posture in towing is stabilized around the attack angle of -5° when the wire-attachment position is determined in the anterior of the buoy, taking the gravity center of the body and transmitter into consideration.
A food economic model including fishery products is developed by expanding IFPSIM which was originally made for analyzing agricultural economic polices. Fishery products are introduced by categorizing fish species according to patterns of supply and demand, by modeling production and demand for typical fish species, and by extending the model to all fishery products. By comparing simulation results and actual data for the period from 1988 to 2002, we confirmed that the developed model simulated the long-term changes in production and prices of each fish categories and the whole marine products with reasonable accuracy. Although future studies are necessary to assess the validity of quantitative results generated in this study, we proposed a valid framework for an economic model of food supply and demand including both agricultural and fishery products. In simulations, using the developed model to forecast food self-sufficiency, it is demonstrated that self-sufficiency in fishery products, which do not rely on feed grain, would make a substantial contribution to overall self-sufficiency in sources of essential animal protein.
Experimental results on the forward speed effect to the longitudinal restoring forces and moments acting on high speed coastal fishing vessels are reported. The restoring forces and moments with and without forward speed were measured with a scaled model of the coastal fishing vessel in head waves. The results show that remarkable forward speed effect exists at the Froude number of 0.5 or over. These measured forces and moments do not improve the ship motion prediction so that it is suggested that added mass and inertia moment could depend on forward speed as well.
When we apply the input-output table analysis for small regions such as fishing villages, we have the following issues: 1) The regional input-output tables have hardly been made, 2) If the regional input-out-put table existed, the industrial sectors, especially fishery and its' concerned industries, are not subdivided into more sectors, 3) To make Input-output tables needs a lot of time and money. In this report, we will explain the methods to make regional input-output tables to reflect characteristics of regional industries and to calculate the economic effects caused by materialization of region development scenarios and the efficient fishery infrastructures by using the input-output tables.