Search

The reproductive cycle and releasing time for effective increase of resource of adult sea cucumber (Apostichopus japonicus) have been studied in the west coast of Korea. Adult sea cucumbers collected in Seocheon-gun April 2013 for first release and in the uncontaminated Taean-gun area in the west coast of Korea. Divers monthly collected the specimens in the released area from December 2013 to November 2014 in order to investigate the reproductive cycle of A. japonicas in Taean-gun. Random specimens were dissected to examine the gonadal developmental stages and discharge rates of the guts and gonads. The reproductive cycle of A. japonicus in both sexes are classified into the following six successive stages in the Taean-gun: (1) Stage I (recovery stage from December to February), (2) Stage II (early growing stage from February to March), (3) Stage III (late growing stage from March to April), (4) Stage IV (mature stage from April to July), (5) Stage V (partly spawned stage in July), and (6) Stage V...

Experiments were carried out examine short-term effects of human chorionic gonadotropin (hCG) and long-term effects of luteinising hormone releasing hormone analogue (LHRHa) on milt production of the tongue sole Cynoglossus semilaevis. In the first experiment, each fish was implanted with a blank cholesterol pellet (control), 100 and 200 μg LHRHa per kg body weight. In the second experiment, fish were injected with either 100, 200, 400 and 800 IU hCG per kg body weight or same volume of marine fish Ringer’s solution. In the first experiment, milt volume was increased in male implanted with 200 μg LHRHa pellet compared with other groups at day 10. Injection of 400 and 800 IU hCG resulted in an increase in the milt volume at hour 96 after the treatment. Although statistical difference is unable to confirm because of small milt volume, compared with the control group, hormone pellet-treated groups had a reduction in the mean spermatocrit (Sct) and sperm concentration (Sc). The results suggest that the increase in milt volume is at least partially gonadotropin (GtH)-dependent and increased milt volume has a relationship with milt hydration.Key words : Tongue sole, Cynoglossus semilaevis, spermiation, hormoneCorresponding author: 061-450-2395, limhk@mokpo.ac.kr2013 .

The ultrastructures of germ cells and the functions of Leydig cells and Sertoli cells during spermatogenesis inmale Kareius bicoloratus (Pleuronectidae) were investigated by electron microscope observation. Each of the well-developed Leydig cells during active maturation division and before spermiation contained an ovoid vesicular nucleus, a number of smooth endoplasmic reticula, well-developed tubular or vesicular mitochondrial cristae, and several lipid droplets in the cytoplasm. It is assumed that Leydig cells are typical steroidogenic cells showing cytological characteristics associated with male steroidogenesis. No cyclic structural changes in the Leydig cells were observed through the year. However, although no clear evidence of steroidogenesis or of any transfer of nutrients from the Sertoli cells to spermatogenic cells was observed, cyclic structural changes in the Sertoli cells were observed over the year. During the period of undischarged germ cell degeneration after spermiation, the Sertoli cells evidenced a lysosomal system associated with phagocytic function in the seminiferous lobules. In this study, the Sertoli cells function in phagocytosis and the resorption of products originating from degenerating spermatids and spermatozoa after spermiation. The spermatozoon lacks an acrosome, as have been shown in all teleost fish spermatozoa. The flagellum or sperm tail of this species evidences the typical 9+2 array of microtubules.

The effect of sudden changes of water temperature (WT) on the survival rate and physiological responses of the red spotted grouper (Epinephelus akaara) were examined by manipulating WT control system for 9 days. Experimental condition was divided in two different regimes at low (from 10°C to 4°C, decreased 1℃/d) and high (from 28°C to 34°C, increased 1°C/d) WT. Survival rate of experimental fishes were observed, and determined the changes of hematological characteristics by analyzing plasma levels of cortisol, glucose, total protein, and electrolytes (Na(+), Cl-, K(+)). No mortality was observed until low WT 6°C (144 h) and high WT 32°C (96 h), and 100% mortality was observed at low WT 4°C (216 h) and high WT 35°C (171 h). Plasma levels of cortisol and glucose increased rapidly as decreasing WT, and the loss of swimming ability and respiration response was observed at low WT 7°C and high WT 34°C conditions.

This study was performed to determine the effect of water temperature condition on survival rate and growth of juvenile geoduck ( Panopea japonica ). Panopea japonica juveniles were bred for 6 weeks at 12, 15, 18, 21, 24 and 27℃ on incubator. Juveniles median lethal times (LT50) were 29 hours in 27℃, 14.5 day in 24℃, 37.4 day in 21℃. Survival rate of water temperature 12, 15 and 18℃ showed a high survival rate in 95.0%, 95.0% and 93.3% at 6 weeks. As a result of culturing for 6 weeks at 12, 15, 18, 21 and 24℃, a daily growth of shell length and total weight was 0.10 mm, 0.12 mm, 0.13 mm, 0.16 mm and 0.14 mm, and 2.21 mg, 2.65 mg, 2.84 mg, 3.13 mg and 2.93 mg. Juvenile shell length and total weight have significantly increased at 15-21℃. However, mortality rate has significantly increased at more than 21℃. As a result, appropriate water temperature for juveniles culturing considered 15-18℃.Key words: Juvenile geoduck, Panopea japonica , Culture, Water temperature, Median lethal time

This study aims to investigate how ovulation induction of sevenband grouper, Epinephelus septemfasciatus varies when treated with different hormonal substances such as ovaprim, pimozide, LHRHa, and HCG. As for LHRHa, we injected it in different concentrations: 50 ㎍/kg, 100 ㎍/kg, 150 ㎍/kg, and 200 ㎍/kg. All hormonal substances including LHRHa were injected into back muscles. As a result, ovulation occurred in all sample groups. The sample group injected with HCG released the largest amount of eggs, and the dimeter of eggs and oil globules were also significantly bigger than those of others. Fertilization rate, embryonic survival rate, and hatching rate were the highest in a LHRHa (100 ㎍/kg) +pimozide (1,000 ㎍/kg) group and buoyant rate in a LHRHa group. Ovulation rate was 100% when LHRHa was injected in different concentrations. The largest amount of eggs was released in 200 ㎍/kg. The diameter of eggs and oil globules were the biggest in 200 ㎍/kg and the smallest in 50 ㎍/kg. Fertilization rate showed no significant difference through all different levels of concentration: 94.6-95.3%. Buoyant rate was the highest in 100 ㎍/kg and embryonic survival rate and hatching rate in 150 ㎍/kg. Based on these experimental results, we concluded that LHRHa in 100 ㎍/kg is the most efficient for the ovulation induction of sevenband grouper.Key words : Sevenband grouper, Ovulation induction, Ovaprim, LHRHa, Pimozide, HCGCorresponding author : 061-690-8977, hwgang@korea.kr 2015 (RP-2015-AQ-034).

The tongue sole, Cynoglossus semilaevis, is an important fishery resource in Korea. About 100 tongue sole sampled from three major habitats along the western coast of Korea were assessed using multiplex assays with 12 highly polymorphic microsatellite loci to explore the population genetic structure of the species; 151 alleles and similar high levels of gene diversity (mean number of alleles (NA) = 10.42, mean expected heterozygosity (He) = 0.78) were detected. Three populations showed significant Hardy–Weinberg equilibrium deviations at four loci. Although a significant difference in the number of unique alleles was observed among populations, genetic population subdivision was low by F-statistics (overall F ST = 0.007, p

Short barbeled grunter, Hapalogenys nitens, is an important fishery resource and it has been regarded as a target marine fish species for prospective aquaculture diversification in Korea, but sustainable fry production is not yet possible. This delay has led to an increase in the need for genetic information about this species. Furthermore, it is necessary to conserve the wild stocks for the sustainable use of the species. In this study, we report 26 novel polymorphic microsatellites with a mean of 4.9 alleles per locus. The mean observed and expected heterozygosity per locus was 0.45 and 0.50, respectively. Cross-amplification revealed variability in others two Haemulidae species. These markers developed can be a valuable tool for conservation genetics and further genetic improvement of these species.

The gonadsomatic index (GSI) of mottled skate was the highest in April, GSI and HSI showed a reverse phase for its reproductive cycle. The fish had one pair of egg capsules, having 1 to 7 fertilized eggs, and spawned all the year round. When surveying the reproductive characteristics of females over 63 ㎝ in disc width, we found the spawning peak was between April to June, and the appearance ratio of egg capsules was the highest in May (32.1%). The eggs were hatched at 8°C, 13°C, 18°C, water temperature (12.8 to 24.2°C), and the best hatching temperature was 18°C. The number of fish hatched was 4 to 5 fish/egg capsules, and the hatching rate was 100%. The sex ratios of hatching larvae were 45.5% female and 54.5% male. Therefore this study will provide fundamental data and information for artificial reproduction of the mottled skate.

Ultrastructural studies of spermatogenesis and the functions of Leydig cells and Sertoli cells were investigated by electron microscope observation. Ultrastructural characteristics of spermatozoa of Larimichthys polyactis (Sciaenidae) have a round head, a nucleus containing highly compact filamentous clusters of chromatin, slightly eccentric nuclear fossa, no acrosome, a short midpiece with a short cytoplasmic channel, and a flagellum showing the classic axoneme structure (9 + 2) and short irregular flagellum lateral fins. The spermatozoon of this species (Sciaenidae) is Perciformes type II: the flagellar axis is parallel to the nucleus, the centriolar complex is outside the nuclear fossa, the proximal centriole is anterior and perpendicular to the distal centriole, and no more than five spherical mitochondria are observed. Each of the well-developed Leydig cells observed during the periods of active meiotic division and before spermiation contains an ovoid vesicular nucleus; a number of smooth endoplasmi...

The reproductive cycle, gonad index, condition index, and the sex ratio in female and male Coecella chinensis, which were collected from the coastal waters of Namhae, the South Coast of Korea, were investigated by histological analysis and morphometric data. Monthly variations of the gonad index and condition index of this species showed similar patterns to that of the reproductive cycle. The reproductive cycle in female and male C. chinensis can be classified into six successive stages: early active stage (April), late active stage (May), ripe stage (June), partially spawned/spent stage (June to August), degeneration stage (August) and inactive stage (September to March). According to monthly changes in relative frequency distributions of ovarian egg diameters of this species, in particular, a number of ripe eggs ranging about 70 µm appear in June, however, in July and August, although the mode of egg diameters ranging about 50 µm appear about 80%, these ripe eggs ranging from 60 µm to 70 µm are gradually decreased during the period from June to August. Therefore, the spawning period of this species is continued from June to August with a peak between July and August when the seawater temperature exceeds about 24.5°C. The sex ratio of female and male individuals was not significantly different from 1:1 (χ 2 = 1.20, p > 0.05). No hermaphrodites were found.

The morphology and taxonomic values of the sperm in male Chlamys (Swiftopecten) swiftii were investigated by transmission electron microscope observations. The morphologies and ultrastructures of the sperm nucleus and the acrosome of this species are the vase type and long cone shape, respectively. Spermatozoa are approximately 45-50 μm long including a sperm nucleus (approximately 2.60 μm long), an acrosome (about 0.63 μm long), and a tail flagellum (approximately 44-47 μm in long). The axoneme of the sperm tail shows a 9+2 structure. In this study, the right and left basal rings in the acrosomal vesicle of this species show electron opaque part (region), and also the anterior apex part of the acrosomal vesicle shows electron opaque part (region). These characteristics of the acrosomal vesicle were found in Pectinidae and other several families in subclass Pteriomorphia. The number of mitochondria in the midpiece of the sperm of this species are four, as one of common characteristics appear in most species in Pectinidae in subclass Pteriomorphia. In addition, the satellite fibres are found near the distal centriole of this species, as have been reported in other species of Pectinidae in subclass Pteriomorphia. Accordingly, structutral characteristics which are found in the acrosomal vesicle, four mitochondria in the sperm midpiece and the appearance of the satellite fibers near the distal centriole of C. (S.) swiftii in Pectinidae (subclass Pteriomorphia), can be employed for phylogenetic and taxonomic analyses as taxonomic key or a significant tool.

To investigate whether the rearing environmental factors (size heterogeneity, rearing density, and feeding frequency) affect the growth and cannibalism of fry in cultured puffer Takifugu obscurus, we conducted three experiments. To examine size effects, we used small (total length[TL] 26.0±0.5mm, body weight[BW] 0.18±0.01g), medium (TL 23.1±0.1mm, BW 0.28±0.01g), large (TL 26.0±0.2mm, BW 0.48±0.01g) and small-large size combination groups. For density, we used size-matched puffers (TL 25.0±0.5mm, BW 0.53±0.03g) and five density were examined ranging from 1.43 to 7.14 individuals/L. For the feeding frequency, we also used size-matched fry and feeding frequencies of three times/2days, one time/day, two times/day, three times/day. We ran each experiment in triplicate and investigated the survival rate, daily food intake (DFI), feed efficiency (FE), and daily growth rate (DGR). The growth of the puffers increased with increasing size, density, and feeding frequency, while cannibalism increased with a greater size gap, density and lower feeding frequency. Therefore, we concluded that size, rearing density, and feeding frequency are major factors influencing growth and cannibalism of the puffer, T. obscurus.

To investigate the effect of drainage spacing and smear on the rate of consolidation and the efficiency of vertical drain method, a series of consolidation tests with a large consolidation chamber and special equipment for inserting mandrels were conducted. As the smeared region increases, total settlement in over-consolidated clay increases whereas apparent change in settlement does not appear in normally consolidated clay. Vertical drain generally accelerates the rate of consolidation, while it could also deteriorate the efficiency of vertical drain method even for the decreasing drainage length and spacing ratio.

The biochemical composition of wild and cultured yellow croaker, Larimichthys polyactis, was analyzed in this study. The moisture contents in wild and cultured yellow croaker was high: and , respectively. The crude lipid contents of wild and cultured yellow croaker were low; moreover, the crude protein and ash contents did nol differ significantly (P>0.05). The total amino acid content of wild and cultured yellow croaker did not differ significantly; however, the cystine content of wild yellow croaker was higher than than of cultured yellow croaker. The essential /nonessential amino acid (E/NE) ratio in wild and cultured yellow croaker was and , respectively. The free amino acid and extractive nitrogen contents of cultured yellow croaker were high and differed significantly. The water soluble vitamin (, , , , C and folate) and fat-soluble vitamin (A and E) contents did not differ significantly. expect for niacin. The niacin content of cultured yellow croaker was higher than that of wild yellow croaker. The fatty acid composition of wild and cultured yellow croaker did not differ significantly The sodium, magnesium, and copper contents in wild yellow croaker were relatively low. In comparison, the calcium, phosphorus and iron contents in cultured yellow croaker were relatively high. Overall, the biochemical composition of wild and cultured yellow croaker did not differ significantly.

The ultrastructure of oocytes during oogenesis and oocyte degeneration associated with follicle cells in female Sinonovacula constricta (Lamarck, 1818) were investigated by electron microscope observations. Ovarian follicles are surrounded by a matrix of vesicular connective tissue cells (VCT cells). VCT cells contain large quantities of glycogen particles and several lipid droplets in their cytoplasm. It is suggested that VCT cells act as a source of nutrients for vitellogenesis during oogenesis. In early vitellogenic oocytes, several coated vesicles, which appear at the basal region of the oocyte, lead to the formation of membrane‐bound vesicles via endocytosis. The uptake of nutritive materials in coated vesicles formed by endocytosis appears through the formation of coated pits on the oolemma during vitellogenesis. During the late stage of oogenesis, yolk precursors (yolk granules), mitochondria and lipid droplets are present in the cytoplasm of late vitellogenic oocytes. In particular, prote...

Physiological responses of mullet Mugil haematocheilus to cold shock in winter were investigated. The experimental mullets were initially acclimated at and then the water temperature was reduced to for cold shock experiment. The stress responses was monitored for nearly 50 hours. The parameters monitored include survival rate, plasma alanine aminotransferase (ALT), aspartate aminotransferase (AST), glucose (GLU), total protein (TP), electrolytes , cortisol and thyroid hormones . With the exception of the TP and electrolytes, most parameters changed significantly during the cold shock. The survival rate did not change from , but decreased significantly below , and was zero at . The plasma AST and ALT concentrations increased remarkably from and from , respectively, and then declined rapidly as the temperature decreased to . The plasma GLU concentration did not change until -0.5`E, and then the concentration increased significantly at . The plasma cortisol concentration increased remarkably from , and then declined at . The plasma thyroid hormones showed two changes during the cold shock. Both plasma 74 concentrations increased remarkably from , then declined rapidly until , while both plasma 73 concentrations decreased significantly from , and then remained significantly lower than the concentration at .

Short barbeled grunter, Hapalogenys nitens, is an economically important fishery resource. In Korea, this fish is in the early stage of domestication, and it has been regarded as the candidate marine fish species for prospective aquaculture diversification. This study presents a preliminary investigation of the future viability of sustainable fry production from short barbeled grunter. We used 12 polymorphic nuclear microsatellite DNA loci to analyze the possible genetic variability between the wild and hatchery-produced populations of short barbeled grunter from Korea and identified 91 alleles. Compared to the wild population, significant genetic changes including reduced genetic diversity (average allele number: 7.42 vs 3.75; average expected heterozygosity: 0.713 vs 0.598, Wilcoxon signed-rank test; P < 0.05) and differentiation [overall fixation index (FST) = 0.088, P < 0.01] occurred in the hatchery-produced population, as indicated by the observation of allele richness, unique allele, heterozygosity, FST, and results of molecular analysis of variance. These findings indicate that genetic drift may have promoted the differentiation between these 2 populations, which may have negative effects on sustainable fry production. Therefore, genetic variations of the wild and hatchery-produced populations should be monitored and subjected to control inbreeding through a commercial breeding program. The information presented by this paper would provide a useful genetic basis for future sustainable culturing planning and management of H. nitens.

In this study, defect formation mechanisms in the ERW (electric resistance welding) process for API pipe production were investigated. The results showed that defects observed in the weld joint of ERW pipe are a main factor in the deterioration of the mechanical properties of welded joints. From systematical research, it was clear that the crucial main defects of ERW pipe are caused by large inclusions with complex compositions after the steel making process and penetrators formed during ERW welding with excessive heat input condition. In order to guarantee the toughness of the weld joints, after theoretical and experimental considerations ERW pipe weld defect reducing methods can be recommended. According to previous test results, it was clear that the hook cracks caused by large inclusions were reduced by selecting the slag composition ratio of CaO and Al2O3 at the eutectoid point during steel making process. On the other hand, in case of the penetrator formation type defects, it was defined that by controlling of the heat input in the optimization range was the best solution for decreasing the penetrator formation.Copyright © 2014 by ASME

The tongue sole, Cynoglossus semilaevis (Cynoglossidae), is one of the most economically important fishery resources in Korea. This study presents a preliminary investigation of the future viability of the complete aquaculture of tongue sole in Korea. Specifically, possible differences in genetic variability between wild populations of tongue sole from Korea and hatchery-produced populations of tongue sole from China were assessed using multiplex assays with 12 polymorphic nuclear microsatellite DNA loci. High levels of polymorphism were observed between the 2 populations. A total of 135 different alleles were found, varying from 5-15 alleles per locus, with some alleles being unique. These findings indicate a high level of genetic variability in both the wild and hatchery-produced populations. Although a considerable loss of rare alleles was observed in hatchery samples, there were no statistically significant reductions of heterozygosity or allelic diversity in the hatchery population compared to the wild population. Moreover, the inbreeding coefficient was very low (FIS = -0.010-0.052) for both populations. However, significant genetic heterogeneity was found between the 2 populations. These findings indicate that genetic drift has likely promoted differentiation between these 2 populations, and might have negative effects on the reproductive capacity of the stock, because genetic factors are important in the production of high quality seed for complete aquaculture. Therefore, aquaculture management should incorporate basic genetic principles into existing molecular monitoring protocols. The information compiled by this study is anticipated to provide a useful genetic basis for future complete culturing plans and management of C. semilaevis in fisheries.