• Journal of fish pathology
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• v.24 no.2
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• pp.121-129
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• 2011

Aquatic animal raised in hatcheries play an important role in supplying seedling to stock enhancement and seed quality, especially, seed health is the key factor for survival in the field after release and for stocking effectiveness. We have inspected the hatchery-reared seeds of 33 marine species and 12 freshwater species for legally designated diseases in stock enhancement program in 2010. Results showed that abalone was the most abundant as 20.0% in the marine species group and then sea cucumber (15.6%), olive flounder (8.4%), rockfish (6.7%), black sea bream (6.3%) and swimming crab (6.1%) were followed. Crucian carp was the most abundant as 19.4%, and then eel (11.8%), Korean bullhead (10.9%), mandarin fish (10.8%), melanian snail (8.4%), catfish (7.7%) were followed in the freshwater species group. The total number of inspection cases for eight pathogens in this study were 2,105 and disqualification cases were 30 by detection of aquatic animals pathogens such as koi herpesvirus (KHV), red sea bream iridovirus (RSIV), white spot syndrome virus (WSSV) or viral haemorrhagic septicemia virus (VHSV).

• Journal of Aquaculture
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• v.13 no.4
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• pp.331-338
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• 2000

To establish an alternate technology for all male seed production of Nile tilapia, Oreochromis niloticus at hatchery scale, the performance of progenies produced by crossing superfemale with sex reversed male was evaluated. Free crossings between 21 superfemales and 7 sex reversed males stocked in an aquarium for 60 days resulted in the production of 93.5 % male progenies, compared to 53.2 % males produced by an equal number of normal females and normal males. Spawning frequency was lower (19 times) in the experimental cross including superfemales than that (24 times) in the control including normal females. Seed production in the experimental aquarium was (3,085) significantly lower than that (3,797) of the control. Both in terms of seeds per female per day or seeds per g female per day, seed productivity did not significantly differ between these groups. The alternate technology involving crossing between superfemale and sex reversed male has proven to be an efficient alternate technology for mass production of all male seeds at the hatchery scale.

• Journal of Aquaculture
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• v.9 no.4
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• pp.445-452
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• 1996

Endogeneous activities of ${\beta}-galactosidase$-like enzyme in various tissues from several finfishes and shellfishes were examined by histochemical analysis based on X-gal staining and by fluorimetric measurement using 4-methylumbelliferyl-${\beta}$-D-galactoside (4-MUG). Species used in this study were 3 freshwater fishes, mud loach (Misgurnus mizolepis), common carp (Cyprinus carpio) and tilapia (Oreochromis niloticus) ; 3 marine fishes, olive flounder (Paralichthys olivaceus), stone flounder (Kareius bicoloratus) and marbled sole (Limanda yokohamae) ; and 4 shellfishes, abalone (Haliotis discus hannai), Pacific oyster (Crassoskra gigas), pearl oyster (Pinctada fucata martensii) and ark shell (Anadara broughtonii). The activities of ${\beta}-galactosidase$-like enzyme in all finfishes examined were significantly different among species, with the wide variations between tissues in a species. In general, the tissues such as kidney, intestine and liver were ones which showed the significantly higher values in 4-MUG fluorimetry and deeper staining patterns in X-gal analysis compared to other tissues. On the other hand, serum and muscle revealed the significantly lower activities than others did, regardless of species. Shellfishes were also found to have endogenous activities of ${\beta}-galactosidase$-like enzyme which were significantly varied depending on both species and organs in a species. Hepatopancreas from all shellfishes examined showed the deepest pattern in X-gal staining and also the highest value in 4-MUG analysis, while activities of ${\beta}-galactosidase$-like enzyme in adductor muscles and mantle muscles from all shellfish species in this study except Pacific oyster were negligible : Pacific oyster had the significant activity of this enzyme in muscle tissues. Putative endogenous lacZ fragment was amplified from both finfishes and shellfishes by polymerase chain reaction (PCR). The molecular size of PCR products was about 510 bp, and there was no difference in size among species examined.

• Journal of Aquaculture
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• v.15 no.4
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• pp.253-260
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• 2002

To find the optimal rearing conditions for Saxidomus purpuratus juvenile, filtering activity was estimated as functions of algal concentration and temperature by measuring the rates of clearance (CR) and ingestion (IR), when S. purpuratus was feeding. The clams were fed on unialgal diet of Isochrysis galbana at 6 algal concentrations (4.6$\times$$10^4$~2.6$\times$$10^6$ cells/ml) and at 6 temperatures (5, 10, 15, 20, 25, and 30^{\circ}C ). Algal concentration significantly affected the CR and the IR at all temperatures. At lower algal concentrations, CR increased, but decreased beyond a particular concentration. The maximum CR ($CR_{max}$) at 5, 10, 15, 20, 25, and 30^{\circ}C were 0.30, 1.73, 5.95, 15.17, 21.12, and 0.33 $l/g/h$, respectively. Below the level of 5.6$\times$10$^{5}$ cells/ml, IR increased as algal concentration increased, but was saturated at higher concentrations. To maintain high growth rate of S. purpuratus, I. galbana should be supplied with more than 5.6$\times$10$^{5}$ cells/ml. The maximum IR ($IR_{max}$) at 5, 10, 15, 20, 25 and30^{\circ}C were $2.2$\times$10^8, $1.5\times$10^9, 3.4$\times$10^9, 4.9$\times$10^9, 5.3$\times$10^9, and 1.0$\times$10^8$ cells/g/h, respectively. As for temperature, both $CR_max$ and $IR_max$ increased remarkably with raising temperature from 5 to 25^{\circ}C, but rapidly decreased at 30^{\circ}C. Between 15 and 25^{\circ}C $CR_{max} and IR_{max}$ were higher and most stable, At this temperature range, the $Q_{10}/s for CR_{max} and IR_{max}$ were 3.5 and 1.6, respectively. Therefore the optimal thermal range for the juvenile is 15~$25^{\circ}C$. The annual variation in IR$_{max}$ predicted by natural seawater temperature shows that inactive period (with lower $IR_max$) lasts for 5 months (from December to April). To ensure higher growth of juvenile during this inactive period at hatcheries, rearing temperature should be elevated to $15^{\circ}C$.>.

• Journal of fish pathology
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• v.15 no.1
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• pp.25-35
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• 2002

Effects of medicinal herb extract on nonspecific immune responses, hematology and disease resistance against Edwardsiella tarda in olive flounder, Paralichthys olivaceus were evaluated. Wormwood, Artemisia asiatica NAKAI and barrenwort, Epimedium koreanum NAKAI were mixed at a ratio of 7 : 3 (w/w) for 2-herbs extract and wormwood, barrenwort, Korean forsythia, Forsythia koreana NAKAI, chrysanthemum, Chrysanthemum zawadskii var. latilobum KITAMURA, peppermint, Mentha arvensis L. var, piperascens MALINV., great burnet, Snaguisorba afficinalis L., Lizard tail. Saururus chinensis BAILL., mulberry, Morus alba L., and star anise, Illicium varum HOOK, f, at the same weight for 9-herbs extract. Two-herbs of 9-herbs extract were prepared by heating after adding 10㎖ of distilled water per g of the herb mixtures. Fish (10.3$\pm$2.5g) were fed the experimental diets supplemented with the 2-herbs or 9-herbs extract at the different concentrations of 0%, 0.1%, 0.5% and 1% per kg diet for 12 weeks. Lysozyme and bactericidal activities of serum, and hematological characteristics were examined during experimental period. After feeding test period, all experimental groups were challenged with E. tarda. Lysozyme activity from the fish fed the diet supplemented with 0.1% or 0.5% of 2-herbs extract was significantly higher than the control. But there was no difference both in bactericidal activity and hematology among each group. Sixty seven % of relative percent survival values (RPS) in the group fed the diet supplemented with 0.1% of 2-herbs was higher than the other group and the control. These results suggest that supplenmentation of 0.1% of 2-herbs extract to a commercial diet may enhance disease resistance in olive flounder. Although both 0.1% and 0.5% 9-herbs extract did not improve non-specific immune reponses, they could enhance disease resistance of 53% RPS, respectively.

• Journal of Aquaculture
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• v.19 no.3
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• pp.205-209
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• 2006

Genetic change from broodstock to hatchery stock of the olive flounder Paralichthys olivaceus and effective number of breeders (Ne) were investigated by the different fertilized-egg collecting methods; E1 (eggs collected one day after spawning) and E2 (eggs collected two days after spawning) using seven microsatellite loci (Kop2, Kop22, Kop18, Kop3, Kop21, Kop9 and Kop26) for the better understanding of stock enhancement. Observed heterozygosity in three stocks ranged from 0.651 at Kop3 to 0.928 at Kop22, with offspring being slightly higher heterozygous over their parents. However, the genetic reduction of offspring was significant. The offspring allele number per locus was reduced to 23.5% for E1 and 17.6% for E2 of their maternal number. Ne to the hatchery stock was estimated to be 21.9 for E1 and 34.3 for E2. The inbreeding coefficients of populations El and E2 were 0.023 and 0.015, respectively. The present study suggests the extension of the egg collection period for a recovery of the genetic diversity in artificially produced offspring.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.2
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• pp.198-203
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• 1999

Gonadal development and reproductive cycle off Gomphina melanaegis collected in the coastal waters of Chumunjin, Korea were investigated monthly from April 1996 to April 1997. G. melanaegis was dioecious, The gonads were located between the digestive diverticula and muscle tissues of the foot, The ovary was composed of a number of ovarian sacs, and the testis was composed of several testicular tubules. The flesh weight rate was reached the maximum in August ($23.0\%$), and then decreased to $19.8\%$ in September. In March, the value was reached the minimum ($17.8\%$) and then increased, The size of mature oocyte was ranged $50\~60\mu$m in diameter and had a germinal vesicle with a nucleolus. Mature oocyte contained a large number of yolk granules and lipid granules in its cytoplasm. The spermatozoon was consisted of a conical nucleus with acrosome, a middle piece containing four mitochondria and proximal and distal centrioles, and a flagellum, Sex ratio (male/female) and minimum size for sexual maturation of G. melanaegis were 0.79 and about 25 mm in shell length, respectively. The reproductive cycle could be classified into five succesive stages: multiplicative (December to March), growing (April and May), mature(June), sprawning (July and August), and degenerative and resting (September to November) stages.

• Journal of Aquaculture
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• v.10 no.4
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• pp.463-472
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• 1997

Floating and hatching rates, size and survival activity index(SAI) of spawned eggs of red spotted grouper, Epinephelus akaara were studied to understand egg qualities during the spawning periods in 1992, 1993 and 1995. The fish spawned from mid-July to mid-August when temperature ranged 23~$28^\circC$. Floating, fertilization and hatching rates were higher in the eggs from early to middle than those from late during the spawning period. SAI ranged 1.8~9.6, and it was closely related to survival rate until mouth operning time (SMOT). Egg diameter decreased gradually with the time of spawning, while diameter of oil globule was constant during the spawning periods. Induced spawnings were carried out with one injection of HCG over 5, 000 IU/kg body weight. Floating, fertilization and hatching rates of the induced spawning eggs were higher than those of untreated ones. Thus, induced spawning method with HCG was recommended for collecting fertilized eggs in bulk. Optimal time for the collection of high quality eggs was supposed to be from early to middle during the spawning periods. Considering that egg qualities were vulnerable within the period, hatchability, incidence of malformed larvae, SMOT and SAI were factors to be considered together to get good quality of eggs.

• Proceedings of the Korean Aquaculture Society Conference
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• 2003.10a
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• pp.72-72
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• 2003

A 10-week feeding trial was conducted to investigate the effects of dietary glucose, dextrin and starch on growth and body composition of juvenile starry flounder. Triplicate groups of fish (average weight, 9.7 g) were fed iso-nitrogenous (53% CP) and iso-caloric (3.8 kcal/g diet) diets containing 20% glucose, 20% dextrin and 5-25% alpha-potato starch with 5-14% lipid levels. Survival was not affected by dietary carbohydrate. Weight gain, feed efficiency and protein efficiency ratio of fish fed the diet containing 20% glucose were the lowest among all groups. The best weight gain was observed in fish fed the diets containing 20% dextrin. Growth and feed efficiency were not affected by dietary -potato starch level. Lipid contents of whole body and liver were not affected by dietary glucose, dextrin and starch at the same level. However, the lipid contents tended to decrease with increasing dietary starch level and those of fish fed the diets containing 5% alpha-potato starch were significantly higher than those receiving 10-25% alpha-potato starch. Liver glycogen content and hepatosomatic index tended to increase with increasing dietary starch level. These results indicate that juvenile starry flounder are able to efficiently utilize dextrin and -potato starch compare to glucose in diets and that alpha-potato starch could be incorporated up to 25% in the diet for optimum growth by juvenile starry flounder.

• Journal of Magnetics
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• v.7 no.3
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• pp.115-125
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• 2002

We proposed a novel method to evaluate the magnetic properties of the initial layer and the columnar structure separately for CoCr-based perpendicular recording media. We show that the thickness of the initial layer and the intrinsic magnetocrystalline anisotropy of columnar structure can be quantitatively evaluated using the plotted product of perpendicular anisotropy to magnetic film thickness versus magnetic film thickness ($K_{u{\bot}}^{ex{p.}}$ $\times$ d$_{mag.}$ vs. d$_{mag.}$ plot). Based on the analyses, it is found that: (1) compared with CoCrPtTa media, CoCrPtB media have relatively thin initial layer, and have fine grains with homogeneous columnar structure with c-plane crystallographic orientation; (2) CoCrPtB media can be grown epitaxially on Ru or CoCr/C intermediate layer, and as the result, the magnetic properties of the media within thin thickness region of d$_{mag.}$ $\leq$ 20 nm is significantly improved; (3) the key issue of material investigation for CoCr-based perpendicular recording media will be focused on how to fabricate c-plane-oriented columnar grains well isolated with nonmagnetic substance in epitaxial-growth media, while maintaining the thermal stability of the media.