• The Korean Journal of Malacology
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• v.26 no.2
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• pp.151-156
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• 2010

For industrialization of the hard clams, Meretrix petechiails (Lamarck), spawning was induced per spawning induction technique in the artificial maturation group administered of parent maturation control and the natural maturation group of which parents were transported for artificial spawning per time period. Then, fertilization rates, hatching rates and D-shaped larva development rates were investigated. In addition, growth and survival rates of larvae were investigated per larva breeding technique. The results of spawning induction by exposure in the artificial maturation group indicated that response rates were relatively higher at 23% and 32% respectively at the 4th hour and the 8th hour of exposure. In terms of water temperature increase, responses began only when the temperature reached $28^{\circ}C$ or higher. In the experiment group administered with both exposure and water temperature increase techniques, response rate was found to be 45% or higher at the 4th hour of exposure and the temperature of $28^{\circ}C$. At the temperatures of 29, 30 and $31^{\circ}C$, significant differences were not observed. Therefore, it was indicated that the response rates of parent hard clams were higher toward water temperature increase than exposure time. As for spawning induction per time period of the transported parent group, response rate and D-shaped larva development rate were the highest at 67.6% and 96% respectively on August 6, 2009. In terms of water temperatures during larva breeding experiment, growth was faster as water temperature was higher. In addition, growth and survival rates were relatively higher at the salinity of 25. In terms of stocking density, growth and survival rates were relatively higher at 5 inds./mL.

• The Korean Journal of Malacology
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• v.25 no.2
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• pp.113-119
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• 2009

Artificial induction of maturation by heating of the hard clam, Meretrix petechiails (Lamarck) broodstock was investigated from 25 May to 30 June in 2008. We experimented maturation by keeping the breeding water temperature at 20, 25 and $30^{\circ}C$ and as the natural water temperature and found the following results. In case of the female, maturation was the quickest in the experiment group of $30^{\circ}C$ and the maturation tended to be slower as the water temperature was lower. The similar trend was displayed among the male. At experiment completion, maturation induction rate was found to be the highest at 46.0% in the experiment group of $30^{\circ}C$ followed by 35.0% in the experiment group of $15^{\circ}C$, 18.0% in the experiment group of natural water temperature and 12.0% in the experiment group of $20^{\circ}C$. During the period of the experiment, the survival rate was of 90% or more in all groups.

• The Korean Journal of Malacology
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• v.27 no.2
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• pp.115-119
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• 2011

To establish technical development for artificial seed production, growth and survival for early young spats of the hard clam, Meretrix petechialis, were investigated by breeding methods. Adult clams were collected at Hasa-ri, Baeksu-eup, Yeonggwang-gun, Jeollanam-do on July 13, 2010, and then transported to the indoor aquarium at the laboratory. Eggs which were taken from mother clams, were inseminated, and after they were fertilized in the aquarium, 60 million bottom-clinging spats ($198{\pm}12{\mu}m$ in shell length) were produced and bred. The breeding experiments were carried out from July 16 to October 4, 2010 for 80 days. The methods of sand box, sand bottom circulation filter, inclosing net, floor were used for the breeding experiments, and the experimental condition of sea water temperature for larvae were at 25, 28, 31, $34^{\circ}C$. Four marine cultured food organisms were used for this study as follows: Isochrysis galbana, Chaetoceros gracilis, Phaeodactylum tricornutum, Tetraselmis tetrathele. According to the experimental conditions, experimental groups of the spats in the early stage were investigated the growth rate and the survival. As the result, the method of the inclosing net section was the fastest (grew up to $2.64{\pm}0.59{\mu}m$ in shell length), followed by sandbox ($2.59{\pm}0.64{\mu}m$, bottom circulating filter ($2.56{\pm}0.52{\mu}m$), and floor ($2.52{\pm}0.56{\mu}m$). The survival was the highest in the experimental condition of sandbox (35.9%), followed by floor (34.6%), bottom circulating filter (29.5%), and inclosing net (9.3%). Eexperimental condition of water temperature of $34^{\circ}C$ showed the fastest growth rate (grew up to $2.70{\pm}0.76{\mu}m$ in shell length), and showed the latest growth rate (grew up to $2.45{\pm}0.41{\mu}m$ in shell length) at $25^{\circ}C$. The survival (%) was the highest under the water temperature conditions at $31^{\circ}C$, and showed the lowest (14.2%) at $34.^{\circ}C$. The growth rate of the experimental group fed the mixture live food was the fastest with shell length $2.52{\pm}0.66{\mu}m$, and that of experimental group fed P. tricornutum showed the latest (grew up to $2.29{\pm}0.43{\mu}m$ in shell length). The survival was the highest (36.9%) under the experiment condition fed mixture live food and experimental group fed T. tetrathele showed the lowest rate (16.2%).

• The Korean Journal of Malacology
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• v.27 no.4
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• pp.353-358
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• 2011

This study is the result of examining the growth and survival rate of larva and spat when supplied with Enriched live food by adding $B_{12}$, chitosan, PSB, and polysaccharides to microalgae (Chaetoceros gracilis, Isochrysis galbana) to raise the survival rate of larva and spat during artificial clam seed production. Microalge (Chaetoceros gracilis, Isochrysis galbana) was strengthened for nutrition with $B_{12}$ 0.1 ppm, chitosan 0.2 ppm, PSB 3 ppm and polysaccharides 1 ppm and was daily supplied for $3{\times}10^3-15{\times}10^3Cells/mL$ and the growth and survival rates were measured. As the result of experiment, the growth of larva did not show much difference with PSB test section $199{\pm}0.59{\mu}m$, $B_{12}$ test section $198{\pm}0.64{\mu}m$, and chitosan $197{\pm}0.52{\mu}m$, survival rate was highest at PSB test section with 99.3%, followed by $B_{12}$ test section 95.9%, and chitosan 94.5%. Growth of early spat was the highest for PSB test section at $2.74{\pm}0.58mm$, followed by polysaccharides $2.67{\pm}0.55mm$, $B_{12}$ $2.54{\pm}0.48mm$, and chitosan $2.49{\pm}0.51mm$, and the survival rate was the highest for PSB test group at 32.1%, followed by $B_{12}$ test section 31.6%, chitosan 28.5%, and polysacharrides 21.4%. From such results, PSB is found to be very effective with low-quality improvement when breeding early spat of clams, and especially for floor-type early spat breeding, it had the effect of suppressing protozoan and germs so that detailed studies from various perspectives should be conducted with various chemicals in the future.