• Proceedings of the KSRS Conference
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• 2004.10a
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• pp.685-688
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• 2004

Fresh water discharge from the sea floor strongly affects a coastal ecology and the diffusion of contaminants. Much fresh water discharge has been found in the edge of Kurobe alluvial fan, in which annual rainfall is over 4000mm and there is abundant groundwater. However, it is difficult to find the groundwater discharge, thus the search of possible areas with some remote sensing tools is required. Because the temperature of the discharge point is relatively low compared with the surrounding sea water surfaces, there is a possibility to detect the area as an irregular zone of thermal infrared images. Two anomalous temperature zones, which have no surface streams from rivers, are detected by ASTER thermal-infrared images. One of them was verified as the groundwater discharge point by dives. In addition, the distribution of water table under the land side of the two areas is also detected as irregular zones by a ground-penetrating radar

• Land and Housing Review
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• v.15 no.1
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• pp.117-134
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• 2024

This study examines the factors contributing to waterfront satisfaction among different generations, utilizing a survey on the use and perception of waterfront areas by residents of apartment houses in Tokyo's coastal region. The variables used in this study are developed through a review of existing literature, focusing on factors related to waterfront usage. Specifically, we select the proximity to the waterfront, duration of stay at the waterfront, and frequency of visits to the waterfront as key variables for investigation. In addition, the study further incorporates aspects related to waterfront recognition, such as the space, user behavior, and management status of the waterfront. Utilizing these variables, we carry out a correlation analysis to investigate the association between generational use and perception of the waterfront and their satisfaction with water-related experiences. The results identify three key factors to enhance waterfront satisfaction: First, to increase visits from both younger and older generations, improving pedestrian access to the waterfront is essential. Second, for middle-aged and older generations, creating waterfront areas closer to their residences can reduce travel distance and time, encouraging more frequent use. Third, maintaining clean and well-kept waterfront spaces is fundamental for all generations to enjoy relaxing experiences, thereby improving overall satisfaction.

• Journal of the Korean Institute of Navigation
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• v.24 no.1
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• pp.1-12
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• 2000

The ships over the certain navigation area or her length are required to carry charts under the relevant laws. Charts are indispensible to the ships and fishing vessel, because their crew should know the water depth and location of obstacle in order to avoid danger in the navigation and fishing area. But it was found that many ships do not carry proper charts onboard according to the research marine accidents files of marine accident inquiry agency, and questionnaire survey. Consequently, many ships run aground on the coast and port. This study examined the present status of the coastal ship and the fishing vessels, and explained some problems in the aspect of the covering area, the place, the number of the selling agent and adjoining chart, as well as the geographical and traffic density, the crew on board the ship's characteristics, and so on. In this study we propose the way to solve the problem. firstly, the category of the fishing vessel which should carry the chart on bard under the related laws are required to be lowered to 10 gross tons. Besides a ship inspector should examine if the charts covering the area where to navigate even when the temporary inspection is done are carried on board property. Secondly, the inspection body or the controlling office of ship's entry and departure should check throughly whether the ships concerned carry the chart on board. Thirdly the fishing vessels should used the fishing charts, and the body concerned should train the offices about how to use chart, especiany the difference between Tokyo datum and WGS-84 datum. Fourthly the customized chart such as an atlas like a map, a calenda-type chart, a small chart, as a coated chart needs to be publish for the safety of small ship and fishing vessel. Fifthly, it is advisable to draw a recommended course in the route where the coastal navigate mainly and in the narrow channel, The adjoining area should be improved, as well as the qualify of the chart paper. Sixthly, publication of additional new chart in the southern part of East Sea, the eastern part of South Sea, the western part of South Sea and middle part of Yellow Sea near Incheon port should be thought over. Seventhly, the number of chart selling agent should be increased for the sake of purchaser in proportion to the number of port, and small correction of charts in selling agent must be carried out completely.

• Ocean and Polar Research
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• v.35 no.3
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• pp.205-217
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• 2013

We investigated the population dynamics of Aurelia aurita in Sihwa Lake from April to October in 2009. Salinity ranged from 5.9 to 30.7 psu at the surface. Abundance of mesozooplankton ranged from 3 to 111,874 indiv. $m^{-3}$. Ephyrae occurred from April to May with the peak in abundance occurring on 17 April. Maximum density of ephyrae was observed near the power transmission towers that are known to be habitats of polyps. Mortality of ephyrae was lower than in other areas because of the abundant prey concentration and the absence of predators. Young medusae occurred from April to July with the peak in abundance occurring on 8 May. Adult medusae occurred from May to July with the peak in abundance on 25 June and they disappeared before the rainy season. Planula occurred only in May and June with the peak in abundance on 25 June. Growth rates of Aurelia aurita ranged from -0.06 to 0.34 $d^{-1}$, and decreased rapidly after May. The period in which adult medusa occurred was restricted, compared with those in other area in Korea (e.g., Masan Bay) and Japan (e.g., Tokyo Bay). In the period of this study, the available food was limited in June and salinity decreased to ca. 20 psu in May because of the beginning of the wet season. We assumed that the exceptionally short period of occurrence of the medusa may be a response of adults to changes in temperature, salinity or food limitation which leads to the precocious maturation of young medusa and the release of planula and that the brief occurrence of medusa was caused by an abrupt decrease in activity after the release of planula.

• The Journal of Fisheries Business Administration
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• v.34 no.2
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• pp.75-90
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• 2003

When we think of fundamental problems of the aquaculture industry, there are several strict conditions, and consequently the aquaculture industry is forced to change. Fish aquaculture has a structural supply surplus in production, aggravation of fishing grounds, stagnant low price due to recent recession, and drastic change of distribution circumstances. It is requested for us to initiate discussion on such issue as “how fish aquaculture establishes its status in the coastal fishery\ulcorner, will fish aquaculture grow in the future\ulcorner, and if so “how it will be restructured\ulcorner” The above issues can be observed in the mariculture of yellow tail, sea scallop and eel. But there have not been studied concerning seabream even though the production is over 30% of the total production of fish aquaculture in resent and it occupied an important status in the fish aquaculture. The objectives of this study is to forecast the future movement of sea bream aquaculture. The first goal of the study is to contribute to managerial and economic studies on the aquaculture industry. The second goal is to identify the factors influencing the competition between production areas and to identify the mechanisms involved. This study will examine the competitive power in individual producing area, its behavior, and its compulsory factors based on case study. Producing areas will be categorized according to following parameters : distance to market and availability of transportation, natural environment, the time of formation of producing areas (leaderㆍfollower), major production items, scale of business and producing areas, degree of organization in production and sales. As a factor in shaping the production area of sea bream aquaculture, natural conditions especially the water temperature is very important. Sea bream shows more active feeding and faster growth in areas located where the water temperature does not go below 13∼14$^{\circ}C$ during the winter. Also fish aquaculture is constrained by the transporting distance. Aquacultured yellowtail is a mass-produced and a mass-distributed item. It is sold a unit of cage and transported by ship. On the other hand, sea bream is sold in small amount in markets and transported by truck; so, the transportation cost is higher than yellow tail. Aquacultured sea bream has different product characteristics due to transport distance. We need to study live fish and fresh fish markets separately. Live fish was the original product form of aquacultured sea bream. Transportation of live fish has more constraints than the transportation of fresh fish. Death rate and distance are highly correlated. In addition, loading capacity of live fish is less than fresh fish. In the case of a 10 ton truck, live fish can only be loaded up to 1.5 tons. But, fresh fish which can be placed in a box can be loaded up to 5 to 6 tons. Because of this characteristics, live fish requires closer location to consumption area than fresh fish. In the consumption markets, the size of fresh fish is mainly 0.8 to 2kg.Live fish usually goes through auction, and quality is graded. Main purchaser comes from many small-sized restaurants, so a relatively small farmer and distributer can sell it. Aquacultured sea bream has been transacted as a fresh fish in GMS ,since 1993 when the price plummeted. Economies of scale works in case of fresh fish. The characteristics of fresh fish is as follows : As a large scale demander, General Merchandise Stores are the main purchasers of sea bream and the size of the fish is around 1.3kg. It mainly goes through negotiation. Aquacultured sea bream has been established as a representative food in General Merchandise Stores. GMS require stable and mass supply, consistent size, and low price. And Distribution of fresh fish is undertook by the large scale distributers, which can satisfy requirements of GMS. The market share in Tokyo Central Wholesale Market shows Mie Pref. is dominating in live fish. And Ehime Pref. is dominating in fresh fish. Ehime Pref. showed remarkable growth in 1990s. At present, the dealings of live fish is decreasing. However, the dealings of fresh fish is increasing in Tokyo Central Wholesale Market. The price of live fish is decreasing more than one of fresh fish. Even though Ehime Pref. has an ideal natural environment for sea bream aquaculture, its entry into sea bream aquaculture was late, because it was located at a further distance to consumers than the competing producing areas. However, Ehime Pref. became the number one producing areas through the sales of fresh fish in the 1990s. The production volume is almost 3 times the production volume of Mie Pref. which is the number two production area. More conversion from yellow tail aquaculture to sea bream aquaculture is taking place in Ehime Pref., because Kagosima Pref. has a better natural environment for yellow tail aquaculture. Transportation is worse than Mie Pref., but this region as a far-flung producing area makes up by increasing the business scale. Ehime Pref. increases the market share for fresh fish by creating demand from GMS. Ehime Pref. has developed market strategies such as a quick return at a small profit, a stable and mass supply and standardization in size. Ehime Pref. increases the market power by the capital of a large scale commission agent. Secondly Mie Pref. is close to markets and composed of small scale farmers. Mie Pref. switched to sea bream aquaculture early, because of the price decrease in aquacultured yellou tail and natural environmental problems. Mie Pref. had not changed until 1993 when the price of the sea bream plummeted. Because it had better natural environment and transportation. Mie Pref. has a suitable water temperature range required for sea bream aquaculture. However, the price of live sea bream continued to decline due to excessive production and economic recession. As a consequence, small scale farmers are faced with a market price below the average production cost in 1993. In such kind of situation, the small-sized and inefficient manager in Mie Pref. was obliged to withdraw from sea bream aquaculture. Kumamoto Pref. is located further from market sites and has an unsuitable nature environmental condition required for sea bream aquaculture. Although Kumamoto Pref. is trying to convert to the puffer fish aquaculture which requires different rearing techniques, aquaculture technique for puffer fish is not established yet.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.17 no.5
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• pp.423-435
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• 1984

The reproductive cycle of the small filefish, Rudarius ercodes was investigated based on the annual variations of gonadosomatic index(GSI) and hepatosomatic index(HSI) by electronic and photic microscophy. The specimens used were collected at the coastal area of Benden island, Sizuokagen, Japan, from September 1982 to August 1983. GSI began to increase from March, starting season of longer daylength and higher water temperature, and reached the maximum value between June and August. It began to decrease from September with the lowest value appearing between November and February without any evident variation. The annual variations of HSI were not distinct in male filefish and were negatively related to GSI in female : HSI decreased in the summer season when the ovary was getting mature and reached the maximum in the winter season when the ovary was getting retrogressive. The ovary consisted of a pair of saccular structure with numerous ovarian sacs branched toward the median cavity. Oogonia divided and proliferated along the germinal epithelium of the ovarian sac. Young oocytes with basophile cytoplasm showed several scattering nucleoli along the nuclear membrane. when the oocytes growing to about 300 ${\mu}m$, nuclear membrane to disappear with nucleus migrating toward the animal pole. The regions of protoplasm were extremely confined within the animal hemisphere in which most of cytoplasms were filled with yolk materials and oil drops. After ovulation, residual follicles and growing oocytes remaining in the ovarian sacs degenerated. But perinucleatic young oocytes without follicles formed were not degenerated, and growing continuously still in the next year. Mitochondria and endoplasmic reticula in the cytoplasm remarkably increased with oocytes maturing and yolk accumulating. Those were considered to be functionally related to the yolk accumulation. Five or six layers of possible vitellogenin, oval-shaped disc structures with high electron density, appeared in the apex of follicular processes stretching to the microvilli pits of mature oocytes. Testis consisting of a pair of lobular structures in the right and left were united in the posterior seminal vesicle, Cortex of testis was composed of several seminiferous tubules, and medulla consisting of many sperm ducts connected with tubules. Steroid hormone-secreting cells with numerous endoplasmic reticula and large mitochondria of well developed cristae were recognized in the interstitial cells of the growing testis. Axial filament of spermatozoon invaginated deeply in the central cavity of the nucleus and the head formed U-shape with acrosome severely lacking, mitochondria formed large globular paranuclei at the posterior head, and microtubular axoneme of the tail represented 9+9+2 type. The annual reproductive cycles could be divided into five successive stages : growth(March to July), maturation(May to September), Spawning(mid May to early October) and resting stages(October to February). The spawning peak occurred from June to August.