Fishing port facilities are the main coastal structures in fishery area forming large stocks for which a considerable degradation is concerned. Introduction of the stock management capable of reducing the life cycle cost and enhancing the life and durability of the existing structures is expected. This paper discusses the future prospects and problems with the stock management when applied to the fishing port on the basis of the actual operations. For a smooth introduction of the stock management to the fishing port facilities, a series of systematic measures are introduced including accumulation/utilization of the surveillance data, appropriate diagnosis of the degradation, rational prediction/countermeasures for the degradation , and estimation/yearly stabilization of the LCC .
Ninety-three coral species have been identifi ed at Okinotorishima (Okinotori Island), an isolated table reef located in the center of the Philippine Sea. The species composition of the island is similar to that of other islands in the northwestern Pacifi c, but the number of species is small in comparison with surrounding islands. The coral fauna at the island is characterized by a unique species composition that is independent of the Ryukyu Islands, mainland Japan, Palau, and the Mariana Islands. No endemic species were found, but the dominant Acropora species (A. aculeus, A. sp. aff. divaricata, and A. globiceps) were morphologically different from corresponding species at the Ryukyu Islands. The relatively low species diversity at the island despite the close proximity to an area of high diversity is explained by its small habitat diversity and isolation from other islands. The island is located in a subtropical gyre and is isolated from major currents. Thus, only coral larvae with a long competency period (as long as 70 days) can settle at the island from surrounding islands. This unique species composition seems to have been maintained for at least the last 7600 years, since the last stage of sea level rise in the postglacial period (Holocene).
In late years, a micro-bubble aeration system attracts attention as a means of improving bottom hypoxic waters. In the present study, we examined the performance of the system applied to a fishing port anchorage where hypoxic slack waters often appear during summer. We performed field experiments and then developed a numerical model capable of reproducing the measured data. Forcing the model, we reproduced the observed hydrodynamic and water quality fields during the operation of the micro-bubble aeration system. From the numerical results, we found that the system can improve the bottom hypoxic waters up to the horizontal scale of 25m. This indicates that the total improvement of the present targeted area would be achieved if 4 to 7 sets of the system are properly allocated covering whole of the area.
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