• The Korean Journal of Malacology
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• v.19 no.2
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• pp.161-169
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• 2003

Seawater and sediment quality analysed was calculated to examinate the present environmental characteristics and pollution load was also calculated to evaluate the effect of farming area on the coastal environment. The measurements for seawater quality demonstrate the coastal environment has relatively eutrophicated with significantly decreased DO (0.2-8.5 mg/l) and elevated COD (9.6-31.2 mg/l) in summer. It was also evident that the water quality in Jindong Bay has been influenced by residues tide from Masan Bay with high metal concentration in August of 2002. Annual total pollution load (land and farm-driven) was estimated at 37,316 ton (SS) /yr: 9,809 ton/yr (26.3%) of land-driven load, 23,576 ton/yr (63.2%) of coastal sedimentation and 3,932 ton/yr (10.5%) of feces of cultural organisms. When all ark shell seedling farms are permitted species conversion to ascidian farm, the pollution load would increase by 196%, which may be another source for accelerating the eutrophication of the environment in Jindong Bay.

• The Korean Journal of Malacology
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• v.18 no.2
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• pp.83-91
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• 2002

Reproductive cycle of natural population and artificial control experiments of gonadal development by the conditions of water temperatures-feeding and starvation of Ruditapes philippinarum were investigated by histological observations. The reproductive cycle of natural population in females and males can be categorized into five successive stages; early active (February to March), late active (April to May), ripe (April to August), partially spawned (May to October), and spent-inactive stage (August to March). In the artificial control experiments, gonadal development of this species was inhibited by the low water temperature (10$^{\circ}C$). In the experimental group which was exposed to artificial high water temperatures of 19$^{\circ}C$ and 22$^{\circ}C$, gonadal development was accelerated by the higher water temperatures and was faster (about one month) than that in natural populations. In the high water temperatures-feeding experimental group, the gonadal developmental phase was faster in the small-size group than that in the large-size group, and was faster in lower water temperature (10$^{\circ}C$)(p=0.01). The gonad developmental phases in the high water temperature (22-28$^{\circ}C$)-starvation experimental group showed faster (paired sample t-test, p=0.004) than those in the high water temperature-feeding group in females and males. In the high water temperature-feeding experimental group of female and male gonadal developments of small sized group were more sensitive than those in large sized group after 42 days cultivation, However, the gonadal development of male was more sensitive to the lower water temperature than female. On the whole, sexual maturation in the high water temperature experimental group was faster than those in the low water temperature group, and showed a significant difference (paired sample t-test, p=0.001) between female and male. In the starvation experimental group after 42 days, gonadal developments in the high water temperature-large male group showed faster than those in the high water temperature-large female group. However, in small size, gonad developmental phases showed the same pattern between feeding and starvation experimental groups. During the main spawning season, in the high water temperature-starvation experimental groups in females and males, their gonadal development showed faster than that in higher water temperature-feeding experimental group regardless of their sexes and individual sizes and showed a significant difference (paired sample t-test, p=0.004).

• The Korean Journal of Malacology
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• v.28 no.2
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• pp.137-143
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• 2012

This study was done to examine the effect of several diets (Phytoplankton = PHY, Shellfish Diet 1800 = INS, Oil type = OTE, Powder type = PTE) on growth, survival rate and biochemical composition of scallop juvenile Patinopecten yessoensis. The highest survival rate were observed in PTE + PHY (90%). The highest shell length and shell height was observed in PHY and PTE + PHY diet (P > 0.05). The growth with PTE and OTE diet was the lowest in shell length and shell height (P < 0.05). On the other hand, the shell width and meat weight were highest in PHY and PTE + PHY, while the lowest in PTE and OTE (P < 0.05). The content of fatty acids such as DHA and n-3 PUFA levels was significantly higher in the juvenile fed on PTE + PHY than in those fed on PHY and INS alone. Also, the total protein ranged 55.5 to 65.2% in PHY + INS, while 44.8%, 47.9% in PTE and OTE respectively. The RNA and DNA contents were the highest in PHY and PTE + PHY, while the lowest in PTE and OTE (P < 0.05). RNA/DNA ratio significantly higher in juvenile with PHY + INS than those with PTE and OTE alone (P < 0.05). The combination of PTE + PHY could improve the growth and survival of scallop juvenile. Our results suggested that PTE could partially replace live algae in bivalve laval rearing.

• The Korean Journal of Malacology
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• v.29 no.1
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• pp.51-63
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• 2013

To assess the effect of environmental factors on the sustainability of cultured production shellfish, we investigated the habitat characteristics of tidal flat (Namhae-po in Taean). We measured the physiochemical parameters (temperature, salanity, pH, dissolved oxygen and nutrients) and the geochemical characteristics (chemical oxygen demand, ignition loss, C/N ratio and C/S ratio). Surface sediments were collected from several site of tidal flat to examine the geochemical characteristics of both the benthic environment and heavy metal pollution. The grain size for research area of tidal flat were similar at the ratio of silt and clay in comparison with the other site of it. The C/N ratio was more than 5.0, reflecting the range arising from the mix of marine organism and organic matter. The C/S ratio (about 2.8) showed that survey area had anoxic or sub-anoxic bottom conditions. The enrichment factor (Ef) and index of accumulation rate (Igeo) of the metals showed that those research areas can be classified as heavily polluted, heavily to moderately polluted, or more or less unpolluted, respectively. Adult surf clam (Mactra veneriformis) density was highest at St. 2 (middle part of the Namhae-po), on the other hand, surf clam spat density was highest at St. 3 (lower part of the Namhae-po). Heavy rain, terrigenous suspended clay with fresh water from neighboring agricultural land, and severe high air temperature during summer could be thought as detrimental causes of spat and adult mortality in Namhae-po tidal flat. We suggested that the growth of shellfish in the tidal flat was effected by the various environmental conditions, so an improvement in the cultured method was needed.

• The Korean Journal of Malacology
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• v.20 no.2
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• pp.111-120
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• 2004

We investigated the reproductive cycle of Corbicula japonica with its gonadal development by histological observations, and the seasonal changes in biochemical mass and foot muscle of the adductor muscle, visceral mass and foot muscle of the clam by biochemical analysis, from January to December, 2003. The reproductive cycle of this species can be classified into five successive stages: early active stage (February to April), late active stage (April to July), ripe stage (June to August), partially spawned stage (July to September) and spent/inactive stage (September to March). According to ANOVA test, there were significant differences (p < 0.05) in total protein, total lipid and glycogen contents among months for all of the visceral mass, adductor muscle and foot muscle. Total protein content was highest in adductor muscle, while lowest in visceral mass. There was no correlation in total protein content between visceral mass and adductor muscle (p = 0.208). However, strong positive correlation was found between adductor muscle and foot muscle (r = 0.769, p < 0.001). In visceral mass, total lipid content was the highest; it was 2 or 3-fold higher than in adductor muscle or foot muscle. The monthly change was also most dynamic in visceral mass. It decreased from January to March (early active stage), and reached maximum in April (late active stage). From May to August (ripe and partially spawned stage), it dradually decreased and then increased again until October (spent/inactive stage). Multiple comparisons showed that total lipid content in visceral mass between all of the adjacent two months was significaltly different (p < 0.05). There were strong negative correlations in total lipid content between visceral mass and adductor muscle (r = 0.687, p < 0.001), and between visceral mass and foot muscle (r = 0.473, p = 0.008). Changes of glycogen content were more or less similar to the changes of lipid contents in visceral mass, adductor muscle and foot muscle, except for April. In April, glycogen content in visceral mass was over four times higher than that in adductor muscle or foot muscle. There was a positive correlation in glycogen content between adductor muscle and foot muscle (r = 0.686, p < 0.001). Especially, total lipid content showed a negative correlation between the adductor muscle and visceral mass. Therefore, these results indicate that the nutrient content of the adductor muscle, visceral muscle and foot muscle changed in response to gonadal energy needs.

• 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.31 no.2
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• pp.103-112
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• 2015

Bay scallop (Argopecten irradians) has been farmed only in the South Sea of Korea. East Sea Fisheries Research Institute (ESFRI) has developed bay scallop aquaculture technologies to extend its aquaculture area to the Southeast Sea of Korea. For the artificial spawning, the water temperature was maintained at $23^{\circ}C$. Over 100,000,000 eggs were spawned through artificial spawning inductions, such as air exposure and thermal shock by rising the water temperature. The fertilization rate was over 91% with nearly 94,000,000 fertilized eggs. The shape of fertilized eggs was spherical with an average diameter of $61.7{\pm}0.05{\mu}m(54.1-67.4{\mu}m)$. Five days after fertilization, the eggs developed into prodissoconch shell, and continuously grew into umbo stage and then umbones stage. After 8 days of fertilization, the size of larva became $179.7{\pm}8.4{\mu}m$ on average ($150.4-204.8{\mu}m$), and the larva formed a foot and an eye spot. The larvae grew to $235.4{\pm}9.7{\mu}m$ in 10 days and attached to adherence material, becoming juvenile bay scallop. The shells grew from 22.71 mm to 72.40 mm in 6 month (June-December). The total weight increased from 2.0 g to 32.7 g at the same period. The daily growth rates of young scallop were $0.35mm\;d^{-1}$ (Apr. to Jun.) and $0.41mm\;d^{-1}$ (Jun. to Aug.), which were comparable to those found in the South Sea. These findings suggest that the bay scallop aquaculture may be suitable in the Southeast Sea of Korea and may provide an additional crop to aquaculturists.

• The Korean Journal of Malacology
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• v.31 no.2
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• pp.93-101
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• 2015

The effects of different stocking densities on the growth and survival rate of the 3-year-old pacific abalone, Haliotis dicus hannai were investigated in marine net cage for a year. Stocking densities in net cage ($2.4{\times}1.2m$) was set 15, 30, 45 and 60 percentage (= per)/sq m (square meter, $m^2$) with share to cross-sectional area per shelter. The water temperature during the testing period was $8.2^{\circ}C-22.1^{\circ}C$, and salinity is $33.5{\pm}0.6psu$, and dissolved oxygen is $7.87{\pm}0.86mg/L$. In the shell length (initial size : $71.50{\pm}2.28mm$) growth and shell breadth (initial size : $46.43{\pm}2.28mm$) of the test abalones, the absolute growth rate (ARG), daily growth rate (DGR) and specific growth rates (SGR) of the 15 per/sq m and 30 per/sq m were higher than those of 45 per/sq m and 60 per/sq m density group (P < 0.05). Also in the weight (initial weight : $35.7{\pm}8.1g$), it showed the same results. In survival rates, it were that 15 per/sq m and 30 per/sq m is significantly higher than 45 per/sq m and 60 per/sq m. Therefore, it was that the 15 per/sq m is optimized stocking density in marine net cages about the 3-year-old pacific abalone over 70 mm size. The result shown that total cross-sectional area under the shelter is based on 15 per/sq m ($2.4{\times}2.4m$, 354 number in a net cage) is suitable for fast growth and survival. But if the economy consider, optimized stocking density would be appropriate to accept 30 per/sq m ($2.4{\times}2.4m$, 710 number in a net cage).

• The Korean Journal of Malacology
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• v.31 no.2
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• pp.83-92
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• 2015

The effect of different intermediated rearing method by expanding the attached floor space in order to highly density culture on the growth characteristics and survival rate of the juvenile abalone, Haliotis discus hannai, were investigated in land-based tanks. The intermediated culture methods was determined thru the shelter counts and layer for 10 month with two replicates : the single layer shelter (SLS), the double layer shelter (DLS), the triple layer shelter (TLS) and the single layer shelter under net cage (SLSNC). In addition, the culture on shallow race way tank had to set up as culture of the ditch raceway tank (CDRT) and the floor race way tank (CFRT). In the growth performance of reared abalone (initial mean shell length $54.18{\pm}7.39mm$ and weight $1.93{\pm}0.14g$) at experimental tanks, that the absolute growth rate (ARG), daily growth rate (DGR) and specific growth rate (SGR) to the shell length and shell breadth was not significant at each experimental tanks except SLSNC. As well as too, weight gain (WG), daily weight gain (DWG) and specific weight gain (SWG) to weight was not significant at each experimental tanks except SLSNC, too. Survival rates of CDRT and CFRT was lower than those of different experimental tanks (P < 0.05). Therefore, these results is showed that high density different intermediated rearing method by expanding the attached floor space for juvenile H. discus hannai was not have difference as growth performance and survival rate both one layer shelter and multi layer shelter. Also, it is considered that shallow race way tank was not useful rearing for the juvenile intermediate culture of H. discus hannai in land based.

• The Korean Journal of Malacology
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• v.31 no.2
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• pp.73-81
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• 2015

This study was conduct to investigate the effect of intermediate culture types on the growth and survival rate of the juvenile abalone, Haliotis discus hannai fed seaweed and artificial diet. Intermediate cultures were to determine there that was to fed seaweed (SW) of artificial diet (A) of floor culture (FC), net floor culture (NFC), double shelter culture (DSC) and indoor net cage culture (INCC) in land-based tank, in two replicate. In the growth performance of juvenile abalone reared through intermediate culture to fed SW of A, that the absolute growth rate ($AGR_{SL}$, $AGR_{SB}$), daily growth rate ($DGR_{SL}$, $DGR_{SB}$), and specific growth rate ($SGR_{SL}$, $SGR_{SB}$) to the shell length (SL) and shell breadth (SB) of experimental groups were not significant. As weight gain (WG), daily weight gain (DWG) and specific weight gain (SWG) to body weight through intermediate culture types in land-based tank was not significant. However, as to survival rate to experimental groups, A-FC was higher than those of different groups (P < 0.05). Therefore, these results is showed that was not difference to growth of juvenile abalone over 2 cm fed seaweed diet and artificial diet according to intermediate culture types. But floor culture with artificial diet indicate that was highest to survival rate, therefore, it is beneficial for higher productivity in floor culture with artificial diet among intermediate culture types.