• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.538-541
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• 2005

Tidal flats develop along the south coast ofthe Korean peninsula. These areas are famous for sea farming. Specially, strong and coherent radar backscattering signals are observed over oyster sea farms that consist of artificial structures. Tide height in oyster farm is possible to measure by using interferometric phase and intensity of SAR data. It is assumed that the radar signals from oyster farm could be considered as double-bouncing returns by vertical and horizontal bars. But, detailed backscattering mechanism and polarimetric characteristics in oyster farm had not been well studied. We could not demonstrate whether the assumption is correct or not and exactly understand what the properties of back scattering were in oyster farm without full polarimetric data. The results of AIRSAR L-band POLSAR data, experiments in laboratory and JERS-l images are discussed. We carried out an experiment simulating a target structure using vector network analyser (Y.N.A.) in an anechoic chamber at Niigata University. Radar returns from vertical poles are stronger than those from horizontal poles by 10.5 dB. Single bounce components were as strong as double bounce components and more sensitive to antenna look direction. Double bounce components show quasi-linear relation with height of vertical poles. As black absorber replaced AI-plate in bottom surface, double bounce in vertical pole decreased. It is observed that not all oyster farms are characterized by double bounced scattering in AIRSAR data. The image intensity of the double bounce dominant oyster farm was investigated with respect to that of oyster farm dominated by single bounce in JERS-l SAR data. The image intensity model results in a correlation coefficient (R2 ) of 0.78 in double bounce dominant area while that of 0.54 in single bouncing dominant area. This shows that double bounce dominant area should be selected for water height measurement using In8AR technique.

• Proceedings of KOSOMES biannual meeting
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• 2004.05b
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• pp.81-84
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• 2004

Control of Sediment is very important in prawn farm due to the eruption of toxic material such as W1ionized H2S, NH3 and NO2-. In this study, column test study, column with filter media such as activated carbon, zeolite, oyster shell and iron chloride to evaluate the reduction of toxicity from sediment ammonia-N(NH3) was effectively removed by Zeolite and oyster shell. It was indicated that ammonium ion(NH4+) was removed by ion exchange of zeolite. And the ammonia in the column of oyster shell was existed as the form of NH4+, which is not toxic for prawn because oyster shell was stably kept around pH 8. Therefore, some of ammonia(NH3) was reduced by oyster shell. Hydrogen sulfide and COD were effectively removed by adsorption of activated carbon and a partial removal of hydrogen sulfide was accomplished by Oyster shell. Phosphorous was removed by activated carbon, oyster shell and iron chloride. In prawn farm, the concentration of ammonia was increased with increase of pH by algae photosynthesis in the column of activated carbon, zeolite and iron chloride, but it was revealed that pH was stably kept in the column of oyster shell.

• Journal of Biosystems Engineering
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• v.38 no.2
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• pp.81-86
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• 2013

Purpose: Recently, domestic and abroad consumption of mushroom has been increasing. Especially, oyster mushroom has been the most consumed product, sharing one third of the mushroom market. The air temperature differences between relative positions of the mushroom farms were needs to be minimal. However, in reality, the air temperature differences ranged from 2 to $5^{\circ}C$. Because of this, the mushrooms are non-uniform growth as well as decrease in both quality and quantity. Although air circulators have been employed by oyster mushroom farms to minimize air temperature differences, no experiments have been performed to illustrate the effect of the air circulators. Methods: This experiment is designed to analyze the effect of the air circulation by constructing a prototype air circulator and measuring the air temperature when the circulator was position at different heights (50 cm, 150 cm, 200 cm) from the floor in the center. Result: The horizontal plane air temperature of the first growing bed when the air circulator was installed 50cm above the floor in the center, once not using the air circulators and the other time using the air circulators, yielded the air temperature differences of $8.6^{\circ}C$ and $1.8^{\circ}C$ and deviations of 2.82 and 0.60, respectively. The third growing bed's air temperature differences were $10.0^{\circ}C$, $1.6^{\circ}C$ and deviations 3.28, 0.64, each respectively. These outcomes proved that the use of air circulators minimized the air temperature difference and deviation. The use of air circulators helped minimize the air temperature differences and the derivations in oyster mushroom farm. Conclusion: The use of air circulators helped balance the air temperature distribution in oyster mushroom farm.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.47 no.6
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• pp.1026-1036
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• 2014

Real-time monitoring for environmental factors (temperature, salinity, chlorophyll-a, etc.) and fugacity of carbon dioxide ($fCO_2$) was conducted at an oyster Crassostrea gigas farm in Goseong Bay, south coast of Korea during 2-4th of November, 2011. Surface temperature and salinity were ranged from $17.9-18.7^{\circ}C$ and 32.7-33.8, respectively, with daily and inter-daily variations due to tidal currents. Surface $fCO_2$ showed a range of $390-510{\mu}atm$ and was higher than air $CO_2$ during the study period. Surface temperature, salinity and $fCO_2$ are showed significant correlations with chl.-a and nutrients, respectively. It means when chl.-a value is high in surface water of the oyster farm, active biological production consume $CO_2$ and nutrients from environments and produce oxygen, suggesting a tight feedback between biological processes and environmental reaction. Thus, factors affecting the surface $fCO_2$ were evaluated using a simple mass balance. Temperature and biological productions by phytoplankton are the main factors for $CO_2$ drawdown from afternoon to early night, while biological respiration increases seawater $CO_2$ at night. Air-sea exchange fraction acts as a $CO_2$ decreasing gear during the study period and is much effective when the wind speed is higher than $2-3m\;s^{-1}$. Future studies about organic carbon and biological production/respiration are required for evaluating the roles of oyster farms on carbon sink and coastal carbon cycle.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.23 no.3
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• pp.253-262
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• 1990

Hardened seed oysters which inhabit the Hansan Bay of Korea and Hiroshima Bay of Japan were cultured at the oyster farm of Nino island near Hiroshima from June, 1972. to June, 1973. The present experiment investigated monthly increment of shell height, shell length, meat weight, moisture, fatness and gonad development of the seed oysters. Environmental factors were also checked to know ecology of the oysters. The oyster farm of Nino island near Hiroshima city showed high water temperautre and low salinity com-paring with the oyster farm of Hansan Bay. Korea. Shell height and shell ten求h of the hardened seed oyster of Hansan Bay grew faster than those of Hiroshima Bay, especially in oyster meat weight. Histological observation on gonads showed little difference in developmental process between the two localities from June through December, 1972, whereas the hardened seed oyster from Hansan Bay has grown rapidly in the development of gonad after February, 1973. It can be concluded that in the viewpoint of seed oysters productivity the hardened seed oyster from Hansan Bay is more effective than that of Hiroshima Bay comparing in seed growth, fatness and developmental process of gonad.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.5
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• pp.773-783
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• 2020

In order to evaluate the recovery of fishing ground environment after the cessation of aquaculture farming, we examined the variation in sediment quality over time using different geochemical factors and investigated whether these factors are indicators of sediment quality recovery. The study area was an oyster Crassostrea gigas, farm in Tongyeong, Geyongsangnam-do, South Korea, where aquaculture activities had been carried out for 20 years, and the changes in water and sediment environment were monitored for 14 months after the abandonment of the farm. The mean water depth was 14 m, with a tidal range of 3 m, and seawater current velocity ranged from 4.7 to 7.0 cm/s. After the abandonment of the farm, total organic carbon and total nitrogen concentrations in the surface sediments decreased significantly over time compared to those in the control site; in particular, immediately after farm abandonment, acid-volatile sulfide concentrations decreased relatively rapidly. Carbohydrate and protein concentrations in the sediments showed no significant changes; however, lipid concentrations markedly decreased. Further studies on other aquaculture taxa and various aquaculture areas are needed to establish new policies for environmental management of fishing grounds, such as relocation of fishing grounds and determination of optimal fallowing periods.

• Journal of the Korean Society for Marine Environment & Energy
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• v.5 no.1
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• pp.68-75
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• 2002

This study were observed to the conditions of organic pollution applying to tile environmental assessments based on macrobenthos around the raft culture ground which became an issue by organic matter input in Jinhae Bay. Three stations, mussel farm, oyster farm and the control station on which rarely culture activities were fixed and have analyzed to the sediment characteristics and macrobenthic communities. Muddy substrates between 6.0 and 6.60 on mean grain size have prevailed to the bottom layer in all stations. The highest organic matter content of 2.8% was observed to the mussel farm while the lowest one of 1.5% was recorded on the control area. As a total, 79 species from seven phyla were identified. Comparing to shell farms, the control station have composed to more diversified community structure. In the mussel and the oyster farm, opportunistic species, living in high organic contents area, Lumbrineris longifolia, Heteromastus. filiformis in polychaetes and Corophium sinense in amphipod were dominated. As results on environmental assessment, in spite of changing to the species composition and densities seasonally, the mussel farm have recorded only to moderately polluted condition.

• The Korean Journal of Malacology
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• v.29 no.4
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• pp.283-289
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• 2013

In order to improve oyster farming condition, estimation of food availability (CC) was carried out in Garorim Bay, Seosan, Korea. The primary production of the waters were ranged from 0.07 to $0.26gC/m^2/day$. A strong tendency was observed that the inner side of the bay was higher at primary production. Estimated food availability was ranged from 0.0424 to 1.655. Temporal shortage in food supply was observed at April with about 15% less than the oysters' requirement, which may be causative of spat mortality after introducing into the farms. Food availability was met the food demand during summer but significant shortage was also observed at after August, which may main causative of retarded oyster fattening in the waters. This study suggested that adjustment of cultural density may be necessary for the improved harvesting of the oyster.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.11 no.4
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• pp.243-247
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• 1978

COD and sulphide contents in the superficial mud in three oyster farms, one near Gajo-do in Chinhae Bay, the second near Eup-do in Koseong Bay and the third near Eogu in Keoje Bay, around the Chungmu area have been monthly determined for seven months from May through November in 1978. Bottom water was also checked for chlorophyll-a, dissolved oxygen, COD and sulphide. In general, large amounts of COD and sulphide in the superficial mud were found in the summer season, COD was 38.1 mg/g dry mud in the farm near Gajo-do, 32.3 mg/g near Eup-do and 25.1 mg/g in Eogu farm and sulphide was 0.313 mg/g dry mud, 0.517 mg/g and 0.132 mg/g respectively. COD and sulphide contents in the farms near Gajo-do and Eup-do were a little over the upper level of the eutrophic range, that is, 30 mg/g dry mud in COD and 0.3 mg/g dry mud in sulphide. It shows that the above two oyster farms were already eutrophicated. However, among three oyster farms no clear difference in bottom water was found.

• Proceedings of KOSOMES biannual meeting
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• 2004.11a
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• pp.101-103
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• 2004