• Korean Journal of Ichthyology
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• v.13 no.3
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• pp.166-172
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• 2001

Parental care of eggs of Chromis fumea (Tanaka) was observed by Skin Scuba gear in August 1995 off Cheju Island. The eggs and larval development were observed in the laboratory at Pukyong National University, Pusan. Eggs were deposited on a flat surface of hard substratum and formed a plain sheet of one layer of eggs. Males showed parental care of the eggs by hovering over the nest and attacking other fishes that approached the nest. The spawned eggs were transparent, elliptical in shape and measured 0.73~0.88 mm in long axis and 0.50~0.56 mm in short axis. An analysis by T-test of the long axis of the egg with time showed a significant difference (p<0.01). However, there was no significant difference in short axis with time. Eggs were reared at water temperatures of $23.0{\sim}25.5^{\circ}C$ and took about 4~5 days from embryonic body stage to hatching. The newly hatched larvae were 1.10~1.61 mm in notochord length (NL) had 21 myomeres, has closed mouth but open anus, preanus length was 45.8% of NL. Melanophores were distributed on the occipital region of head, the eye, the peritoneal region, and along the ventral contour. The larvae absorbed the yolk material and oil globule in 3~4 days after hatching and became postlarvae. On the third day after hatching, the larvae had attained 1.9~2.4 mm in NL, had 25 myomeres, and showed rapid growth. By the ninth day after hatching, the larvae had attained 2.9 mm in NL, had an swimbladder in the dorsal margin of ventral region, the preanus length was 37.9% of NL, and their melanophores were enlarged and reduced in number.

• Korean Journal of Ichthyology
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• v.19 no.4
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• pp.343-349
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• 2007

Embryonic and larval developments on Pacific cod, Gadus macrocephalus are described from laboratory-reared specimens. The eggs (1.075~1.168 mm in diameter) were weakly adhesive, almost spherical in shape, transparent and unpigmented, showing a pale yellow yolk without oil globules. Hatching was occurred 220 hrs after fertilization at $9.8^{\circ}C$. The newly hatched larvae (3.72~4.40 mm in total length, TL) had 43~47 (11~13+32~34) myomeres, mouth and anus which was not yet opened. The yolk was completely absorbed at 4.58 mm TL, and transformed to postlarval stage. Locations of the anus and second dorsal fin origin, and distinctive growth of the larvae head were observed at 5.48 mm TL with melanophores in the gill cover and upper region of the occipital. In addition, melanophores were distinctive in the ventral region and caudal fin base at 6.88 mm TL. All fins were formed with a complete set of fin rays having the following counts (D. 3~7-12~14-13~14; A. 13-15) at 11.54 mm TL. Both lateral line and barbel of lower jaw were observed at 15.07 mm TL.

• Korean Journal of Ichthyology
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• v.27 no.1
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• pp.10-15
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• 2015

Giant grouper (Epinephelus lanceolatus) is a endangered species considered as a vulnerable grade-organism in the International Union for Conservation of Nature (IUCN) red list. As a fundamental baseline study for establishing a giant grouper broodstock management system, the efficiency for parentage analysis was evaluated by using microsatellite makers previously available in this species. The eight microsatellites generated a total 52 alleles from 32 individuals, the mean expected heterozygosity was 0.663, and mean inbreeding coefficient was 0.011, consequently suggesting that the present broodstock has retained the high level of genetic diversity. However, our analysis also recommended the collection of more broodfish for more stable brood line, since the estimated value of the effective population size was proven to be 35. The average probability of identity was $6.85{\times}10^{-11}$. NE-2P and NE-PP of paternity non-exclusion probabilities were 0.00835 and 0.00027, respectively. As the result of principle coordinate analysis, the genotype of broodstock was not overlapped, suggesting that the management system of giant grouper based on eight selected microsatellite markers might be effective, although further validation with extended number of broodfish might also be needed in future. Data of present study could be a useful basis to avoid the unwanted selection of broodfish that possess close genetic relationship with current broodstock, and consequently to establish effective broodstock management system allowing the production of progeny with high genetic diversity.

• Korean Journal of Ichthyology
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• v.27 no.1
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• pp.1-9
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• 2015

The morphological and skeletal development and larvae and juvenile of Sebastes koreanus were studied. The Sebastes koreanus were caught at Yeosu-si, Jeolla-namdo from March in 2014. Larvae beared at water temperature of $13.5{\sim}15.5^{\circ}C$ (mean $14.5{\pm}0.1^{\circ}C$). The just beared larvae were 6.38~6.43mm(mean $6.40{\pm}0.02mm$, n=5) in total length and their mouth and anus were already opened. They began to eat rotifer and transformed to postlarva stage. 5 days after bearing postlarvae was measured 6.45~6.49 mm (mean $6.47{\pm}0.02mm$) in total length. 15 days after bearing postlarvae was measured 6.55~6.72mm(mean $6.64{\pm}0.08mm$) in total length. 60 days after bearing juvenile was measured 15.5~20.0 mm (mean $17.7{\pm}2.25mm$) in total length with dorsal fin rays X IV-12~13; anal fin rays III-7; caudal fin rays 16.

• Korean Journal of Ichthyology
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• v.21 no.3
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• pp.149-157
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• 2009

Larvae and juveniles of the filefish Thamnaconus modestus were reared for 64 days after hatching (DAH) in order to determine the activity of four enzymes (trypsin, pepsin-like enzyme, lipase, amylase) during ontogeny. Larvae were fed on rotifer Brachionus plicatilis from 2 to 26 DAH, Artemia nauplii from 10 to 64 DAH, and then gradually changed to pelleted feed from 40 DAH. Temperature was kept between $21.5{\sim}24.2^{\circ}C$ Activity of trypsin and lipase was found in larvae 4 DAH ($6.0{\pm}1.4unit$) and 6 DAH ($4.5{\pm}1.4unit$), respectively. The evolution of activity in both enzymes showed a profile marked by drastic increases between late larval and early juvenile stages. Pepsin-like enzyme activity was found at 10 DAH and drastically increased from 28 DAH, corresponding with the early juvenile stage of T. modestus. Interestingly, developmental changes in the pepsin-like enzyme activity coincided well with increases in the number of gastric glands. Amylase activity was found at 10 DAH and was maintained at a low level up to 28 DAH, followed by a drastic increase from 28 DAH to 40 DAH. It might be concluded that a drastic increase in trypsin and pepsin-like enzyme activities, and a corresponding increase in the number of gastric glands reflects a higher somatic growth of T. modestus during the early juvenile period.

• Korean Journal of Ichthyology
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• v.21 no.4
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• pp.221-226
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• 2009

Six microsatellite DNA markers were used to investigate the genetic variability between wild populations and cultured stocks of olive flounder Paralichthys olivaceus. The average of observed (Ho) and expected heterozygosity (He) ranged from 0.722 to 0.959, and from 0.735 to 0.937, respectively. There was no distinguishable difference between the wild populations and cultured stocks in terms of the observed and expected heterozygosities. However, number of alleles per locus differed markedly between the two fish groups: 19.7 to 21.8 for the wild populations and 12.0 to 14.7 for the cultured stocks. This result gives important information concerning the production of seedling for the improvement of genetic diversity in this species.

• The Korean Journal of Malacology
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• v.32 no.3
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• pp.203-209
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• 2016

Growth and survival of the hard shelled mussel spat were investigated to confirm the possibe spat culture in seawater pond from September 2014 to April 2015. Also, we measured simultaneously environmental factors including water temperature, salinity, dissolved oxygen, pH, DIN, DIP, chlorophyll a, and abundance and dominant species of phytoplankton in seawater pond every month. Ranges of water temperature and salinity were $4.0-23.4^{\circ}C$ and 18.8-25.2 psu, respectively, which were rather lower than the reported optimal level. Monthly measured survival rates in all the spat cages were over 90%. Concentration of chlorophyll-a and abundance of phytoplankton were very high, and dominant species phytoplankton were cryptomonads and nanoflagellates. These dominant species were considered to be good food organisms for the bivalve spat. The experimental cage stocked 100 individuals per basket ($2,700ind.\;m^{-2}$) hanging in bottom of seawater pond revealed the highest growth in shell height ($7.63{\pm}4.65mm$), but all experimental cages stocked below 200 individuals per basket ($5,400ind.\;m^{-2}$) did not show statistically significant difference. We may expect that seawater pond would be one of the best culture ground for bivalve spats when appropriate measures are available.

• The Korean Journal of Malacology
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• v.32 no.3
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• pp.197-202
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• 2016

This research reports the intersexuality of bivalves, such as Crassostrea gigas, Mytilus galloprovincialis, Rupiditapes philippinarum, Gomphina veneriformis and Barnea davidi discovered during the process of investigating the ecological health status of coastal waters of Korea. In intersex ovaries, the opposite germ cells were observed either individually or in groups in the interfollicular space and inside the oogenic follicle. Oocytes in the intersex testis were at the previtellogenic or initial vitellogenic stage. They were either scattered individually or in groups in the interfollicular space and inside the spermatogenic follicle. The intersexuality in C. gigas was 10.4% (n = 19/183), while female (12.2%, n = 6/49) exhibited a higher proportion than male (9.7%, n = 13/134). The intersexuality in M. galloprovincialis was 31.7% (n = 19/60), while female (36.4%, n = 12/33) exhibited a higher proportion than male (25.9%, n = 7/27). The intersexuality in R. philippinarum was 11.2% (n = 11/98), while male (16.7%, n = 7/42) exhibited a higher proportion than female (7.1%, n = 4/56). The intersexuality in G. veneriformis was 28% (n=30/107), while male (31.5%, n=17/54) exhibited a higher proportion than female (24.5%, n=13/53). The intersexuality in B. davidi was 18.4% (n = 7/38), while female (35.7%, n =5 /14) exhibited a higher proportion than male (8.3%, n = 2/24).

• The Korean Journal of Malacology
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• v.32 no.3
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• pp.189-195
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• 2016

The growth of manila clam Ruditapes philippinarum inhabiting culturing ground was studied in west coast Gomso tidal flat of Korea, from August 2000 to July 2001. The density of the clam was the highest in November 2000, showing a monotonic decrease afterwards over the study period. Mean density was $1,224ind./m^2$ during the study period. Size frequencies of the clam showed a unimodal distribution, and its mode increased with shell growth over time. Although the growth of shell length of manila clam was monotonic, the growth rates decreased between July 2001 and February 2002 and increased from March 2002. The biomass of the clam also increased with time, in which the increments becoming larger since March 2002. The clam shell length had linear relationship to shell height, and had logarithmic relationship to total weight, meat wet weight, dry meat weight, and AFDW. Condition index of the clam increased continuously until April, decreasing afterwards in 2001. The pattern was similar in 2002. Based on fluctuations in condition index, the spawning time of manila clam in Gomso tidal flat is inferred to be between May and October. These results suggested that optimal harvests can be made before summer season when growth decreased and mass mortality occurred, after 24 months of seed shell release.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.6
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• pp.626-632
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• 2015

The International Maritime Organization (IMO) has adopted several regulations for the prevention of air pollution from ships. In addition, there is a requirement for shipping liners to reduce greenhouse gas emissions. Accordingly, we need to take measurements to ensure that the steps taken are both efficient and environmentally friendly. It has been determined that the application of the Miller cycle in diesel engines has the effect of both reducing the amount of NOx and improving thermal efficiency. However, this method requires a considerably larger charge air pressure. Therefore, we consider a two-stage turbo-charging system, which not only results in a high charging pressure, but also improves the part load performance with an exhaust-gas bypass system or the application of the Miller cycle. Because of complications associated with the two-stage turbo-charging system, it is complex and difficult to realize a design that optimizes matching between diesel engine and turbo-chargers. Accordingly, it is necessary to perform a quantitative analysis to determine the effects and optimal conditions of these different systems in the early stage of system design. In this paper, we develop a simulation program to model these systems, and we verify that the results of this program are reliable. Further, we discuss methods that can be employed to improve its efficiency.