• Journal of Aquaculture
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• v.11 no.3
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• pp.391-400
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• 1998

This study was performed to investigate the effects of environmental parameters on the growth of Pacific oyster, Crassostrea gigas at old suspended culturing grounds of Korsung Bay and newly deveoped bottom, culturing grounds of Haenam region located in southern coast of Korea. The Kosung Bay was semiclosed and water exchange occurred through the small mouth and the current speed was very slow as the value of below 0.5kn. Haenam was opened and littoral zone. Current speed of the surroundings of this Bay about to 5.0knand transparency was low with the mean depth of 1.2m by the resuspension of the sediments. Water temperature and salinity regimes were suitable for oysters at those sites, however the mean value of those parameters and seasonal fluctuations was high at Kosung. The mean concentration of dissolved oxygen in survey area was above $5.0mg/\ell$. In Kosung, however, it was decreasing in June and showed the minimum with the concentration of $4.0mg/\ell$ in August at the bottom layer and recovered in September. Eutrophication parameters such as COD were 1.44 mg/l at this location. This mean value was higher than that of the Haenam Bay's $0.96mg/\ell$. The men value of chlorophyll-$\alpha$ at Haenam was two times higher than the other sites. Growth of shell height and meat weight of oysters at Kosung Bay were higher and the fatness was lower compared to thost of Haenam. As a result, absolute growth of oysters was high at Kosung and allometric growth, such as fatness, was good at Haenam. Low water temperature and frequent exposure of oysters to the air during ebb tide may retard the shell growth. On the other hand, relatively high food availability was profitable for the fatness at haenam site.

• Asian-Australasian Journal of Animal Sciences
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• v.26 no.12
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• pp.1659-1664
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• 2013

The objectives of this study were to investigate color patterns of shell and mantle edge pigmentation of a Pacific oyster, C. gigas, and to estimate variance components of the two colors. A sample of 240 F0 oysters was collected from six aquaculture farms in Tongyeong, Korea to measure shell color and mantle edge pigmentation. Among the F0s, male and female individuals with black (white) shell and black (white) mantle edge were selected and mated to generate three F1 full-sib black (white) cross families (N = 265). Two and four F2 cross families (N = 286) were also produced from black and white F1 selected individuals, respectively. Variance component estimates due to residuals and families within color were obtained using SAS PROC VARCOMP procedures to estimate heritability of shell and mantle edge pigmentation. In the F0 generation, about 29% (11%) had black (white) color for both shell and mantle edge. However, in the F1 and F2 black (white) cross families, 75% (67%) and 100% (100%) of oysters had black (white) shell colors, and 59% (23%) and 79% (55%) had black (white) mantle edge, respectively. Spearman correlation coefficients between shell and mantle edge color were 0.25, 0.74, and 0.92 in F0, F1, and F2 generations, respectively, indicating that, with generations of selection process, an individual with black (white) shell color is more likely to have black (white) mantle edge pigmentation. This suggests that shell color could be a good indicator trait for mantle edge pigmentation if selection of both the colors is implemented for a couple of generations. Estimates of heritability were 0.41 and 0.77 for shell color and 0.27 and 0.08 for mantle edge pigmentation in the F1 and F2 generations, respectively, indicating that, in general, significant proportions of phenotypic variations for the shell and mantle edge colors are explained by genetic variations between individuals. These results suggest that the two color traits are inheritable and correlated, enabling effective selection on shell and mantle edge color.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.49 no.3
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• pp.351-358
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• 2016

The aim of this study was to verify the performance of Teleaulax amphioxeia as prey for Brachionus plicatilis and for the larvae of the bivalves (Pacific oyster Crassostrea gigas and Manila clam Ruditapes philippinarum) to select the best of five T. amphioxeia strains. The five strains of T. amphioxeia were collected from the coasts of Korea, purecultured and then fed to the rotifer and bivalve larvae. The density and fecundity rate of the rotifer fed on strain 01 were the highest. The instantaneous growth rate of the rotifer fed strain 08-2 was the highest. The maximum density and fecundity rate of the rotifer fed strain 08-2 were significantly higher than those fed Chlorella ellipsoidea, while instantaneous growth rate showed the opposite pattern. Survival rates of the Manila clam larvae fed each strain of Teleaulax showed no significant difference between strains. Survival rates of the Pacific oyster fed Teleaulax were significantly higher than those fed Chaetoceros sp., but lower than those fed I. galbana. This study indicates that strain 08-2 showed better growth for B. plicatilis and better survival for the bivalve larvae than did the other strains, and that T. amphioxeia can also be used as a prey organism for rotifers or bivalve larvae.

• Journal of Aquaculture
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• v.21 no.4
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• pp.203-212
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• 2008

A nutritional demand of oyster, Crassostrea gigas larva as part of research for improving of utilization of microalgae being used for the artificial oyster seed production. The change of body growth and biochemical compositions of larvae were investigated during larvae rearing in hatchery. The larvae were cultured in 60 M/T tank and fed mixture 6 different phytoplankton species, Isochrysis galbana (30%), Cheatoceros gracilis (20%), Pavlova lutheri (20%), Phaeodactylum triconutum (10%), Nannochryis oculata (10%) and Tetraselmis tetrathele (10%). The initial feeding amount was $0.3{\times}10^4cells/mL$ at three times a day to D-shaped larva and the feeding amount had been increased 30% gradually every two day since the larvae were raising. The larvae were developed from D shape to pediveliger stage for 12 days. The daily growth of shell length and hight were $5.8{\sim}30.8\;{\mu}m$ and $8.7{\sim}31.4\;{\mu}m$, respectively and weight gains were changed from D shape to pediveliger as follow: wet weight was $0.52{\sim}15.0\;{\mu}g/larva$, dry weight was $0.2{\sim}6.5\;{\mu}g/larva$, and ash free dry weight was $0.1{\sim}8.5\;{\mu}g/larva$. The larvae growth pattern shown a logarithmic phase from D shape to umbone stage but after that stage shown a exponential growth aspect. The crude protein, crude lipid and nitrogen free extract (NFE) of larvae during rearing periods were analyzed as $6.1{\sim}10.6%$, $0.6{\sim}1.1%$ and 1.0-2.7%, respectively. And the total amino acid contents of the larvae during rearing periods were in order as glutamic acid $1.26{\sim}2.24%$, aspartic acid $0.97{\sim}1.70%$, and methionine $0.12{\sim}0.33%$. Of the total fatty acid in the analyzed larvae, the saturated fatty acid (SSAFA) was decreased from 54.3% (D shaped larvae) to 17.1 % (pediveliger) as larvae development but the total mono-unsaturated fatty acid (${\Sigma}MOFA$) and Poly-unsaturated fatty acid (${\Sigma}PUFA$) were increased from 29.9% and 7.8% to 40.6% and 45.6%, respectively. By the way the each fatty acid of the larvae were composed of palmitic acid $9.89{\sim}36.95%$, oleic acid $12.17{\sim}32.29%$, linoleic acid $1.96{\sim}33.55%$, EPA $2.17{\sim}11.58%$ and DHA $1.95{\sim}4.51%$. As a result of this study, the larvae of oyster were demanded a various nutrients for healthy growth and the feeding control, expecially after umbone stage larvae are a rapidly growing time, is very important for success of artificial seed production.

• The Korean Journal of Malacology
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• v.17 no.1
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• pp.19-26
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• 2001

To study the growth of transplanted Pacific oysters, Crassostrea gigas, we sampled Korean and Japanese oysters attached in Chinhae Bay near Gaduk Island and in Seto inland sea in Japan, respectively, suspended in Pukman Bay. Water Temperature ranged from 11.2 to 27.8$^{\circ}C$ (mean 19.84 ${\pm}$ 5.47$^{\circ}C$) on the surface, and 11.1 to 23.6$^{\circ}C$ (mean 18.31 ${\pm}$ 4.18$^{\circ}C$) on the bottom. Salinity ranged from 31.45 to 34.57 (mean 33.10 ${\pm}$ 1.16) on the surface, and from 31.69 to 34.35 (mean 33.24 ${\pm}$ 1.06) on the bottom. salinity was the lowest in September and October, and the highest in December. Growth of oysters in shell height showed a significant difference after being suspended at the farm, reaching 70.3 ${\pm}$ 12.5 mm in the Korean oysters and 96.2 ${\pm}$ 14.6 mm in the Japanese oysters in December. While the Korean oysters showed relatively low growth rate and cessation of growth after sudden growth between June and July, the Japanese oysters showed continuous growth during the whole farming period, although stepwise growth was observed. It was not until September that meat weight showed a significant difference between the two. After September, there was a sudden increase in the Japanese oysters, reaching 7.5 ${\pm}$ 2.9 g in December, but growth of the Korean oysters showed slow growth rate during whole farming period, reaching 4.6 ${\pm}$ 1.9 g in December. here was an obvious decrease in the meat weight of Japanese oysters in December, which might be attributed to restriction of food. Condition factors rebounded in October in the Korean oysters and in September in the Japanese oysters, respectively, attaining 12.8 in the Korean oysters and 15.3 in the Japanese oysters at the end of investigation on December. Shell length-height regression equations were as follows: Korean oysters: S$\sub$h/=2.922S$\sub$t/,-4.8024 (r$^2$= 0.8541) Japanese oysters: S$\sub$t/=3.623S$\sub$h/,-5.1239 (r$^2$=0.7782) This showed the possibility of morphological transformation in the shell of the Korean oysters since shell height was longer than those reported by Bae et al. (1976) and Lee et al. (1992).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.31 no.4
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• pp.567-573
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• 1998

Cold storage of concentrated food phytoplanktons is a useful technique in supplying food organisms for artificial shellfish seed. One month after preservation at $4^{\circ}C$, we have measured survival rate of the concentrated food phytoplanktons, Pavlova lutheli, Isochrysis galbana, Isochrysis aff, galbana and Chaetoceros calcitrans. Thereafter we determined survival rate of oyster lavae fed fresh and concentrated diets and fatty acid compositions of the fresh and concentrated food phytoplanktons. Survival rate of concentrated planktons ranged from $23\%$ to $31\%$ after one month at $4^{\circ}C$. The survival rate of oyster larvae fed cold stored food appeared generally higher than those fed fresh harvested food. Especially, the highest survival rate were found in the larvae fed cold stored concentrated I. aff. galbana. EPA and DHA increased after cold storage and the highest level of DHA was detected in I. aff. galbana. As DHA can role as an important factor in determing nutritional value, it would be better to use concentrated I aff, gaibana kept in cold refrigerator for oyster seed production.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.3 no.2
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• pp.129-136
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• 1970

As an attempt to determine if the morphological differences between the southern and western oysters are due simply to the local ecological factors or are based on their fundamental genetic nature, oyster seeds produced in 1968 at Tong-Young, Ye-Chun, and Ko-Hung on the south coast and at Kan-Wol-Do on the west coast were cross-transplanted during May of 1969 to compare their growth. The spats were placed in plastic baskets which permitted free water flow through and the baskets hung from a wooden rack located at a tidal zone of less than I hour exposure at a depth chosen to keep the baskets submerged in water at all times. Twice a month the growth of the spats were measured along with the air and water temperature and salinity. The early summer spats, which were $17-240\%$ larger, in size, than the late summer spats at the time of cross-transplantation, grew more slowly than the late summer spats when exposed to identical environmental conditions, shortening the initial gap to a $5-20\%$ level as the first year of the growth phase came to an end in December. The growth of the Kan-Wol-Do spats lagged considerably behind the southern spats at all localities tested, whereas there were no significant differences among the latter groups. This suggests that the morphological differences between southern and western Pacific oysters in Korea are a manifestation of genetic variety and that Pacific oysters cultured along the south coast are of an identical variety as they are commonly believed to be. The seasonal changes in temperature and salinity even during rainy season in both the southern and western coastal areas are well within the range suitable for successful spawning, and spat fall. However, since the results were based on twice-a-month measurements with no data covering the critical period before and after spawning, they can only serve to indicate at best the general pattern of changes in the environmental conditions of each growing area.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.30 no.5
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• pp.794-803
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• 1997

Long line suspended culture of oysters has been started commercially in Hansan-Koje Bay since 1969. However, its Annual production has been decreased and culturing periods extended in recent years. So, we investigated environmental parameters and food organisms to identity the causes of poor fatness of oysters in Hansan-Koje Bay from February to November, 1994. As the result, the Water quality of Hansan-Koje Bay was found to be good for culture. For example, the mean concentration of COD was $1.35mg/\ell$, phosphate phosphorus was $0.30{\mu}g-at/\ell$ and dissolved inorganic nitrogen was $4.68{\mu}g-at/\ell$. However, the Hwado island and the inner part of the Hansan-Koje Bay were found to be eutrophicated due to various contaminants transported by land-based activities. But in the central pan of the Hansan-Koje Bay where the oyster farms Have been developed densely, the level of nutrient concentration was very low. During the study period, the dominant species of phytoplankton was Chaetoceros spp. with the percentage of $72.6\%\~87.8\%$ and the mean values of Chlorophyll-a concentration and phytoplankton standing crops were $2.05mg/m^3\;and\;188ind./m\ell$, respectively. The distribution of these parameters also showed similar trends those of nutrients. Especially, chlorophyll-a contents was very low with the concentration of below $0.5mg/m^3$ at central part of the Bay, Juklimpo. The fatness of oysters and the eutrophic index in this area were $18.1\%$ and 0.54, respectively. These values were lower than those of other culturing farms in the southern coastal areas in Korea. Therefore, we estimated that the insufficient food supply due to the low level of nutritional status was the major factors affecting the poor fatness of the Pacific oysters in Hansan-Koje Bay.

• The Korean Journal of Malacology
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• v.32 no.3
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• pp.231-240
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• 2016

Techniques were developed for holding and conditioning of Pacific oysters, Crassostrea gigas, in a closed recirculating system. Experimental adults were used 500 oysters ( x two system, total 1,000 oysters) which were collected in $20^{th}$ March 2016 from long-line aquaculture farm at the south coast of Korea. During conditioning periods concentrated live microalgae as Isochrysis sp. $15{\times}10^7cells/mL$, Tetraselmis sp. $2{\times}10^7cells/mL$ and Pheaodactylum sp. $18{\times}10^7cells/mL$ were added 5 L every day, respectively which micro algae were functioned as diets and biological filter. Over all experimental periods total water exchange rate was 21.3% (daily 0.5%). Over 42 days conditioning, female and male oysters were maturated 90.9% and 94.4%, respectively. Survival rate was 98.7%. Mean shell hight (8.3 mm), total wet weight (19.2 g), meat wet weight (5.0 g) and shell wet weight (13.6 g) were significantly increased (P < 0.05). Water quality parameters including the water temperature ($22.1{\pm}0.4^{\circ}C$), salinity ($24.9{\pm}04$), dissolved oxygen (5.1-7.9 mg/L) and pH ($7.93{\pm}0.15$) were kept stable. Concentration of dissolved inorganic nutrient as ammonia (1.96-0.35 mg/L), nitrite (0.03-0.16 mg/L), nitrate (1.34-0.47 mg/L), DIP (0.42-0.03 mg/L) and silicate (3.83-0.00 mg/L) were significantly decreased throughout experiment except nitrite which was increased (P < 0.05), but nitrogenous components stayed below toxic levels (ammonia 0.0-5.5 mg/L, nitrite 0.0-460.0 mg/L) which indicated that closed recirculation system with microalgae based bio-filter could supply sufficiently environment condition to holding and conditioning of oyster.

• Journal of Aquaculture
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• v.8 no.4
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• pp.355-366
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• 1995

In order to identify some suitable diatoms as a live food source, effects of seven diatom species (Chaetoceros simplex, Navicula incerta, Phaeodactylum tricornutum, Nitzschia closterium, Skeletonema costatum, Thalassiosira pseudonana, Thalassiosira weissflogii) were examined on specific growth rate, mean celt volume, chemical composition and general fatty acid composition. In cell volume. T. pseudonana was the smallest $(125{\mu}m^3)$ and T. weissflogii the largest $(824{\mu}m^3)$. However the specific growth rate of the largest diatom was the lowest (0.5016/day), and that of S. costatum was the highest (0.9928/day). The crude protein content of seven diatom species varied from $18.96\%$ (T. pseudonana) to $24,4\%$ (T, weissflogii). The crude lipid content of C. simplex was the highest $(8.43\%)$, and that of T. pseudonana was the lowest $(3.13\%)$. The total content of polyunsaturate fatty acids which are important for bivalve larvae was higher in C. simplex than those in other species. The total percent of polyunsaturate fatty acids from N. incerta and T. weissflogii was relatively lower than that from other species. Dietary value of seven diatom species were finally examined with Pacific oyster larvae Crassostrea gigas. In this experiment, C. simplex showed the highest survival rate and growth, and the larvae feed on S. costatum and T. weissflogii showed the poorest results. This results C. simplex could be more useful live food for bivalve larvae than other diatom species tested.