• The Korean Journal of Malacology
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• v.28 no.3
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• pp.277-291
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• 2012

Aquaculture is challenged by a number of constraints with future efforts towards sustainable production. Global climate change has a potential damage to the sustainability by changing environmental surroundings unfavorably. The damaging parameters identified are water temperature, sea level, surface physical energy, precipitation, solar radiation, ocean acidification, and so on. Of them, temperature, mostly temperature elevation, occupies significant concern among marine ecologists and aquaculturists. Ocean acidification particularly draws shellfish aquaculturists' attention as it alters the marine chemistry, shifting the equilibrium towards more dissolved CO2 and hydrogen ions ($H^+$) and thus influencing signaling pathways on shell formation, immune system, and other biological processes. Temperature elevation by climate change is of double-sidedness: it can be an opportunistic parameter besides being a generally known damaging parameter in aquaculture. It can provide better environments for faster and longer growth for aquaculture species. It is also somehow advantageous for alleviation of aquaculture expansion pressure in a given location by opening a gate for new species and aquaculture zone expansion northward in the northern hemisphere, otherwise unavailable due to temperature limit. But in the science of climate change, the ways of influence on aquaculture are complex and ambiguous, and hence are still hard to identify and quantify. At the same time considerable parts of our knowledge on climate change effects on aquaculture are from the estimates from data of fisheries and agriculture. The consequences may be different from what they really are, particularly in the temperature region. In reality, bivalves and tunicates hung or caged in the longline system are often exposed to temperatures higher than those they encounter in nature, locally driving the farmed shellfish into an upper tolerable temperature extreme. We review recent climate change and following environment changes which can be factors or potential factors affecting shellfish aquaculture production in the temperate region.

• Journal of the East Asian Society of Dietary Life
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• v.11 no.4
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• pp.289-294
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• 2001

Yields of shells, appearance of the shellfishes, mineral contents of the shells and their hot water extracts were determined in six shellfishes such as corb shell(CS). short neck clam(SNC). taste clam(TC), ark shell(AS). top shell(TS) and oyster(OY) from the western coast of Korea. Yields of shells in shellfishes were 70.I~80.5% but yields of TC was the lowest as 40.7%. The highest among weight of the shell the shellfishes was the TS(26.2g) and the lowest weight was TC(5.6g) Colors of CS, SNC, TC. AS. TS and OY were yellowish brown, brown, black. greenish brown and gray. respectively. Ca content of the shell of shellfishes was 36.23~38.78% and the content of K and Na were 0.23~4.54% and 1.48~l.59%, respectively. Contents of Na, Mg, Fe. Mn, Zn, Cu. P and S were in the range of 0.01~0.21%. It also contained heavy metals, such as Pb(1.90~7.75 ppm), Cd(0.5~4.50 ppm), As (1.40~4.30 ppm), Se (0.2~l.50 ppm). Cr(1.00~8.30 ppm) and Hg(0.002~8.2 ppm), Ca content in hot water extracts of shell of shellfish was the highest in TC(2,448 mg/100 g), and the lowest in SNC(115 mg/100 g). K content in TC extracts was the highest with the levels of 952 mg/100 g. P content of TC and SNC were 201 and 0.36 mg/100 g, respectively. The contents of Pb, As, Se and Cr were the highest in the extracts of TC and were 110. 40. 90, 20 $\mu$g/100 g, respectively. But Cd was not detected in the extracts of SNC.

• Proceedings of the Korean Aquaculture Society Conference
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• 2005.05a
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• pp.74-75
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• 2005

• The Korean Journal of Malacology
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• v.20 no.2
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• pp.125-130
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• 2004

Arkshell, Scapharca broughtonii spats were placed in natural environmental condition for 30 days from July 28 to August 27, 2004, in order to estabilish intermediate culture technique. Growth and survival of the spats in different intermediate culture areas with various culture methods were measured. Water temperature of studied area ranged from 24.1 to 28.5$^{\circ}C$, salinity was 15.4 to 33.3 psu, dissolved oxygen was 3.92 to 12.6 mg/l. Scapharca broughtonii spats cultured in Yeosu developed the best, 10.15 ${\pm}$ 1.12 mm in average shell length, and the highest survival was recorded as 77% in Namhae. Shell lengths of the Scapharca broughtonii spats cultured in the water depths of 2, 5, and 10 m were 7.14 ${\pm}$ 1.14 mm, 6.98 ${\pm}$ 1.74 mm and 6.27 ${\pm}$ 1.33 mm, and the survivals showed 75.5%, 77.0% and 76.5%, respectively. When 1 mm, 2 mm, and 3 mm-sized spats were cultured for 30 days in water depth of 5 m, the shell length increased to 6.73 ${\pm}$ 1.46 mm, 6.98 ${\pm}$ 1.74 mm and 7.04 ${\pm}$ 1.19 mm, and survivals were 67.0%, 77.0% and 58.5%, respectively. The shell lengths of spat cultured for 30 days in mesh sizes of 1 ${\times}$ 1 mm, 2 ${\times}$ 2 mm and 3 ${\times}$ 3 mm, 5 m below the surface were 8.14 ${\pm}$1.23 mm, 8.26 ${\pm}$ 1.19 mm and 8.78 ${\pm}$ 1.16 mm, and survivals were 41.5%, 43.0% and 44.5%, respectively.

• The Korean Journal of Malacology
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• v.27 no.2
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• pp.131-141
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• 2011

Boring caracteristics, boring rate, and predation, rates on the valves of the seed and adult clams of Meretrix petechialis by Glossaulax didyma didyma in the shellfish aquafarm and the indoor rearing aquarium were investigated by various morphometric data. The investigations were carried out from June to September, 2007. The morphology of drilled holes on the valves of M. petechialis showed the crater type as seen in the spats of Ruditapes philippinarum and M. lusoria. The sizes of the outer diameters of holes were greater than the inner diameters of the holes on the valves of M. petechialis in the shellfish aquafarm and the indoor aquarium at the laboratory. On the whole, the sizes of the holes on the valves of the seeds of M. petechialis was smaller than those bored holes on the adult valves. The location of the bored holes on the valves of the seeds varied widely with the the sizes of the individuals of M. petichialis, while most of holes on the valves of adult clams were located near the umbo position of the valves of the clams in the shellfish aquafarm and the indoor aquarium at the laboratory. On the whole, the outer and inner diameters of the bored holes increased with increase of shell lengths of the clams in the shellfish aquafarm and the indoor rearing aquarium at the laboratory. The authors could confirm experimentally the boring snail, G. didyma didyma, drilled the seeds and adult clams of M. petechialis. In the experiments for 15 days (three times repeated) in the indoor rearing aquarium at the laboratory, the mortality of dead shells to total shells of M. petechialis by boring snail Glossaulax didyma didyma was totally average 41.5%, and percent of drilled shells to total dead shells of clams by the boring snail was average 47.1%. Of total shells, percent of drilled shells to total shells of clams by the boring snail was totally average 19.3%. Predation of G. didyma didyma were greater at night than the day time. Average 0.5 seed and adult individuals of M. petewchialis were consumed per G. didyma didyma, per day. Predation varied with shell lengths of M. petechialis and shell widths of G. didyma didyma.

• The Korean Journal of Malacology
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• v.29 no.1
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• pp.77-82
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• 2013

In this study, growth-line analysis was carried out on the hard clam (Meretrix petechialis) recovered from the Neolithic Age Daejuk-ri Shell Middens, Seosan, Korea, with aim to determine the seasonality of shellfish collection and site occupation. Growth increments of 206 specimens of the clam were examined. The marginal index (MI) of the archaeological specimens was calculated and was compared to the monthly marginal index of modern specimens under the assumption that the growth pattern was the same as it is today. MI of the archaeological specimens ranged from 0.13 to 1.29 and was divided into four categories: < 0.63, spring; 0.63-0.76, summer; 0.76-0.89, fall; $$\geq_-$$ 0.89, winter collection. As a result, of 206 specimens, 170 specimens (82.5%) represented spring, 18 (8.7%) summer, 10 (4.9%) fall and 8 (3.9%) winter collection. The results suggest year-round shellfish collection at the sites, with an emphasis on spring. Considering these results it can be inferred that the sites were occupied throughout the year.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.42 no.1
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• pp.8-14
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• 2009

To prevent the food poisoning originated by consumption of shellfish contaminated with domoic acid, the quantitative analysis of domoic acid is to be very important. The stability of domoic acid at different temperature, pH and light was investigated using high performance liquid chromatography (HPLC). The mean recoveries of domoic acid in the methanol extracts from oyster (Crassostrea gigas), blue mussel (Mytilus edulis), short neck clam (Ruditapes philippinarum) and ark shell (Scapharca broughtonii) were 85.4-104.5%, 94.8-101.2%, 91.0-104.6%, and 95.7-109.6%, respectively. The working solutions of domoic acid standard were very stable for one month at $-18^{\circ}C$, $4^{\circ}C$, and room temperature. And domoic acid in the methanol extract from oyster was stable for a day at $4^{\circ}C$ and room temperature, and for a week at $-18^{\circ}C$. Therefore, this implies that quantitative analysis for domoic acid must consider the storage conditions of the standard solutions and the methanol extracts from shellfish. The standard solutions adjusted to pH 3-9 were also stable after heating at $121^{\circ}C$ for 30 min. The effect of light exposure on domoic acid was tested by exposing the methanol extracts to light. Domoic acid degraded slowly when the samples were kept in the dark (brown vial). However, following the light exposure the photodegradation became more rapid; no detectable domoic acid remained in $1.0{\mu}g/mL$ of methanol extract after 5 hours.

• The Journal of Fisheries Business Administration
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• v.51 no.2
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• pp.71-87
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• 2020

Oysters are the most abundantly harvested type of shellfish in Korea. As export of this marine product increases, oysters have greatly contributed to an increase in fishing income. As the oyster aquaculture industry has rapidly grown since the late 1990s, issues of oyster-shell processing that occur in production processes have re-emerged as important topics in the oyster industry. The amount of oyster shells harvested in 2019 is estimated to be approximately 300,000 tons. With reductions in demand for pyrolytic fertilizer and feed, which are currently the greatest sources of demand, unprocessed shell quantities have doubled compared to 2018, causing them to be an issue once more. Such oyster-shell processing also incurs great costs, and a total of forty-six billion three hundred fifty million Korean won (46,350,000,000 KRW) has been provided from 2009 to 2020 for the use of oyster shells as a resource. According to current Korean laws, oyster shells are considered to be industrial waste if more than 300 kilograms are sent out in a day. Collection and processing must be conducted by a waste-consignment company. Consequently, there are many limitations to the use of oyster shells in Korea as a resource. However, in Japan, only oyster-shell waste is regulated by waste-processing As a result, local governments may apply exceptions when utilized as organic matter. Consequently, in Japan, oyster shells are being used as resources in more diverse fields than in Korea. This study observes the conditions and problems of oyster-shell processing in Korea and attempts to find new domestic oyster-shell resource solutions in light of Japan's recycling practices.

• The Korean Journal of Malacology
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• v.20 no.2
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• pp.121-124
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• 2004

Water temperature tolerance of spats of the Manila clam, Ruditapes philippinarum was investigated in the different temperature groups, 15, 20, 25, 30 and 35$^{\circ}C$. The survival rates of the groups were 99.7%, 91.0%, 88.7%, 73.3% and 0%, respectively (p < 0.05). When the temperature of the water decreased from 15$^{\circ}C$ to 5$^{\circ}C$, the survival of spats was higher than when the temperature increased. The growth and survival of spats were investigated in different types of bottom substrates in the tanks. The spats grew the best in the polyvinyl plates, the average shell length was 3.9 ${\pm}$ 0.4 mm. In the FRP tank bottom and sand bottom, the average shell lengths of spats were 3.6 ${\pm}$ 0.3 mm and 3.2 ${\pm}$ 0.3 mm, respectively. The best survival of spats cultured in the FRP tank bottom (22.9 g) and in the polyvinyl plates (20.6 g) (p < 0.05).

• The Korean Journal of Malacology
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• v.22 no.2
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• pp.175-182
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• 2006

Artificial induction of maturation by heating of the ark shell, Scapharca broughtonii (Schrenck) broodstock was investigated from 10th March to 21th May in 2004. Maturity at the fixed water temperature group of $23^{\circ}C$ was 60.5％, and it was the highest in maturity among experimental groups cultured for seven weeks. The proportions of organism surviving to start of S. broughtonii in the raised water temperature experimental groups (20 and $23^{\circ}C$) were over 90.5％, as similar to the control group (natural water temperature, 84.8％). But, the proportions of organism surviving to start of S. broughtonii in the fixed water temperature experimental groups (20, 23, and $26^{\circ}C$) were decreased with the increasing of the water temperature. In the fixed water temperature experimental groups of $26^{\circ}C$, the survival was 18.1％. Base on these results, the fixed water temperature of $20^{\circ}C$ (accumulated water temperature; $1,295^{\circ}C$) was the best condition for artificial induction of sexual maturation.