• The Korean Journal of Malacology
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• v.32 no.2
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• pp.83-93
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• 2016

For the continuous stable production of oyster, estimation of food availability (F) was carried out in Goseong Bay, south of coast Korea. Primary productivity ranged from 0.07 to $0.44gC/m^2/day$ (average $0.25gC/m^2/day$), lowest in July and highest in January. The distribution of primary productivity at Goseong Bay showed the pattern of "high in the south and low in the north." Food availability (F) was $F{\leq}0$, indicating insufficient food supply, from August to November and F > 0 from January to April. Continuous insufficient food supply was observed at 18 oyster farms in the southern part of the bay and 4 in its northern part. Mortality at the oyster farms was 56% on the average, and around 58% of death occurred during November when food supply was insufficient. The optimal population of cultured oyster per unit flow area was calculated to be $110-115indiv./m^2$ (198-201 indiv./string). When the sea area was divided into 3 regions (A, B, C) according to carrying capacity, the carrying capacity of (A) regions was $52-53indiv./m^2$ (93-95 indiv./string), (B) regions was $142-144indiv./m^2$ (255-259 indiv./string), and (C) regions was $198-202indiv./m^2$ (356-363 indiv./string). In particular, (A) regions showed extremely low productivity. For continuous stable oyster farming at Goseong Bay, it is necessary to control point and non-point source pollution through continuous environmental monitoring and to adjust harvest according to the base carrying capacity during the season of high water temperature.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.35 no.4
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• pp.327-335
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• 2002

Effects of available food on growth of commercially cultured Pacific oysters, Crassostrea gigas in Goseong Bay on the south coast were studied using a numerical model. levels of total protein, carbohydrate and lipid in particulate organic matter in the water column as well as chlorophyll a concentration were determined for estimating total available food for oyster growth. Environmental parameters including water temperature, salinity and total suspended solid were also monitored for the model. Oyster growth was also monitored by means of measuring shell length and tissue wet weight increase on a monthly basis. Simulation results from the numerical model indicated that chlorophyll a is not a good representative of available food for the oysters in Goseong Bay. In contrast, available food in the water column measured by filtration of the organic particles and analyzed in terms of total lipids, carbohydrates and protein was well matched with simulated oyster growth in the Bay which is similar to observed growth. The model also suggested that oysters have relatively low retention efficiency of $50\%$ or less. This result indicates that oysters in the bay utilize only a part of food particle available in the water column, as reported in other studies.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.50 no.3
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• pp.263-269
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• 2017

The mineral contents, and free amino acid, and fatty acid composition of rack and bag or suspended cultured oysters Crassostrea gigas were compared. The moisture content did not change much from 82.8% to 86.3% in the different culture methods. The glycogen level was low 4.7% during rack and bag culture but high 7.2% during suspended culture. The sodium level was the highest during suspended culture, while copper and zinc level were highest during rack and bag culture. The taurine level was 1,385-1,375 mg/100 g in oyster cultured using the rack and bag method, but that in the market sample was lowest at 1,015.8 mg/100 g. Hydroxyproline, glutamic acid, proline, glycine, and alanine were detected at high levels in the experimental oysters. The polyunsaturated fatty acid content was similar among samples. The docosahexaenoic acid level was 14% with rack and bag culture and 12% with suspended culture, whereas the eicosapentaenoic acid level was 15% with rack and bag culture and 20% with suspended culture. The atherogenic index (AI), thrombogenicity index (TI), and hypocholesterolemic/ hypercholesterolemic (h/H) ratio were important factors in the nutritional evaluation. The AI and TI values were 0.5-0.2, and the h/H ratio were 2.0 and 2.4 with the rack and bag and suspended culture, respectively.

• Fisheries and Aquatic Sciences
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• v.8 no.4
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• pp.189-194
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• 2005

Protein, lipid classes, and fatty acid composition, including n-3 highly unsaturated fatty acids (HUFAs), were analyzed in the soft parts, which we differentiated as the adductor muscles and 'other portions,' from the cultured pearl oyster after the pearl was harvested and before the nucleus was grafted to evaluate the nutritional qualities of the soft parts. Total lipid content was higher in the other portions of the soft parts ($1.25-1.26\%$) than in the adductor muscles ($0.58­0.65\%$) in both pearl oyster samples, whereas protein content was higher in the latter ($15.5­18.7\%$) than in the former ($11.2-13.9\%$; P<0.05). The percentage of total lipids (TLs) consisting of phospholipids (PLs) was higher in the adductor muscles ($60.4-68.3\%$) than in the other portions ($40.6-47.0\%$), but the percentage of nonpolar lipids (NLs) was higher in the other portions of the soft parts. The prominent lipid classes were free sterol (FS) and triglyceride (TG) in the NLs and phosphatidylcholine and phosphatidylethanolamine in the PLs. The adductor muscles contained high levels of FS and all PL classes, while the other portions contained high levels of all NL classes, especially TG (but not FS; P<0.05). The prominent fatty acids were 22:6n-3 ($17.2-24.9\%$), 16:0 ($8.35-15.8\%$), 20:5n-3 ($7.95-14.9\%$), 18:0 dimethyl acetal (DMA, $4.79-13.5\%$), 18:0 ($4.50-6.16\%$), and 20:4n-6 ($4.36-5.43\%$). The percentages of 22:6n-3, 20:4n-6, and 18:0 DMA were higher in the adductor muscles than in the other portions of both pearl oyster samples, while those of 20:5n-3 and 16:0 were higher in the other portions (P<0.05). The levels of these food components were similar to those of other bivalves or were higher, especially the protein content, indicating that the soft parts of pearl oysters, which are currently wasted, have food value.

• 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.

• Fisheries and Aquatic Sciences
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• v.16 no.2
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• pp.131-135
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• 2013

The presence of ostreid herpesvirus 1 (OsHV-1) and the percentage of viral DNA detected in Pacific oyster Crassostrea gigas adults were investigated monthly between May and November 2012 at three locations along the southern coast of Korea. Among 210 oysters examined by polymerase chain reaction (PCR) analysis, OsHV-1 DNA was detected in only one oyster collected in August. The low detection rate of OsHV-1 DNA was consistent with the lack of reported OsHV-1-associated disease in C. gigas cultured in Korea. The sequence of the present PCR product amplified with the C2/C6 primer pair was identical to that of OsHV-1 ${\mu}Var$ except for one nucleotide, and the sequence amplified with Del36-37F2/Del36-37R showed a 605-bp deletion as in OsHV-1 ${\mu}Var$. Although these sequence data are insufficient to determine genotype, the results suggest that the herpesvirus detected was similar to OsHV-1 ${\mu}Var$. This is the first report on the presence of OsHV-1 in adult Pacific oysters cultured in Korea.

• Fisheries and Aquatic Sciences
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• v.2 no.2
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• pp.135-141
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• 1999

In order to investigate the composition of extractive nitrogenous components in the diploid and the triploid oysters, Crassostrea gigas, cultured at the south coast of Korea, the whole edible part (whole body) was analyzed into extractive nitrogen, free amino acids, oligopeptides, ATP and its related compounds, quaternary ammonium bases, and guanidino compounds using specimens collected from April to May of 1992. The major free amino acids in the diploid and the triploid were taurine, proline, alanine, glycine, glutamic acid hypotaurine, glutamine, arginine, aspartic acid, and $\beta-alanine$. There was no conspicuous difference in the constituents of free amino acids between the diploid and the triploid. A lot of hypotaurine was detected in the diploid and the triploid of oyster and the contents of them were 107 mg and 123 mg/100g, respectively. The compounds, glycinebetaine, homarine and trigonelline were found in both the diploid and the triploid. Among them, glycinebetaine was the most prominent in all the samples. The amount of protein, glycogen, extractive nitrogen, oligopeptides, ATP and its related compounds, and free amino acids in the triploid was higher than that of the diploid (p<0.10)

• Journal of Marine Bioscience and Biotechnology
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• v.2 no.4
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• pp.263-266
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• 2007

Vibrio vulnificusis a causative agent of serious diseases in humans resulting from the contact of wound with seawater or consumption of raw seafood. Several studies aimed at detecting V. vulnificus have targeted vvh as a representative virulence toxin gene belonging to the bacterium. In this study, we targeted the rpoS gene, a general stress regulator, to detect V. vulnificus. PCR specificity was identified by amplification of 8 V. vulnificus templates and by the loss of a PCR product with 36 non-V. vulnificus strains. The PCR assay had the 273-bp fragment and the sensitivity of 10 pg DNA from V. vulnificus. SYBR Green I-based real-time PCR assay targeting the rpoS gene showed a melting temperature of approximately $84^{\circ}C$ for V. vulnificus strains. The minimum level of detection by real-time PCR was 2 pg of purified genomic DNA, or $10^3$ V. vulnificus cells from pure cultured broth and $10^3$ cells in 1g of oyster tissue homogenates. These data indicate that real-time PCR is a sensitive, species-specific, and rapid method for detecting this bacterium using the rpoS gene in pure cultures and in infected oyster tissues.

• The Korean Journal of Malacology
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• v.26 no.2
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• pp.107-114
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• 2010

To evaluate the culture conditions in oyster-farming waters, chemical and biological measurements were made in seawater and oysters from six bays around Tongyeong in November and December 2003. Nutrient levels in the seawater were higher in the western area than in the eastern area, in contrast to particulate organic matter and dissolved oxygen levels. The mean total polycyclic aromatic hydrocarbon ({\sum}PAH) content of the oysters was 194.5-375.9 ng/g dry weight, with four-ring compounds constituting 34.1%-79.6% of PAH. Despite wide temporal variations, a "western > eastern" spatial distribution of PAH was apparent. These low concentrations of PAHs indicate that Tongyeong waters are pristine in terms of PAH contamination. Among the hemocytic biomarkers, only lysosomal activity was significantly reduced in Hansan-Goje Bay, but did not correlate closely with PAH content. This finding indicates that the impact of PAH on cultured oysters is negligible around Tongyeong waters.

• International Journal of Industrial Entomology and Biomaterials
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• v.8 no.1
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• pp.61-66
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• 2004

Bacillus thuringiensis 656-3 which was isolated from a soil sample of mushroom house and showed high toxicity to mushroom flies, Lycoliella mali and Coboldia fuscipes, was surveyed for insecticidal effect in the oyster mushroom house.3. thutingiensis 656-3 was mass-cultured in the fermenter containing soybean cake(2%) and wheat bran (2%) as media source. Semi-for-mutation of B. thuringiensis 656-3 was performed with metamorphic starch only. When the formulation suspension containing $5{\times}{10^7}$ cfu was sprayed on the mushroom in mushroom house, the insecticidal effect of B. thuringiensis 656-3 to mushroom flies,1. mali and C. fuscipes, was maintained over 90% by the fifth day after starting spraying. The yield of oyster mushroom house with B. thuringiensis 656-3 was significantly increased compared to control. B. thuringiensis 656-3 represents a powerful biological insecticide for the control of mushroom flies.