• Fisheries and Aquatic Sciences
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• v.9 no.1
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• pp.7-13
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• 2006

Using biochemical methods, we determined the potential of local female shrimp populations as breeding stock to select the best adult prawns for improving larval production. As condition indexes, we selected total RNA, DNA, their ratio, and trypsin activity. The DNA content in the pleopods of each local population was similar, i.e., between $0.90{\pm}0.06\;and\;1.02{\pm}0.04(SE){\mu}g/mg$. In comparison, the RNA contents differed markedly between $2.00{\pm}0.09$ and $0.96{\pm}0.08\;{\mu}g/mg$. Therefore, the RNA/DNA (R/D) ratio in the pleopod could be used as a condition index because it represents a biochemical characteristic of the population. The mean pleopodal R/D ratio of the Goheung population was the highest at $2.52{\pm}0.19$, which indicated the best condition. Trypsin activity was influenced little by shrimp condition and more by the amount of food ingested. The gonadosomatic index (GSI) and R/D ratio in the gonads provided offsetting information about the instantaneous gonad maturity. The Goheung population had the highest instantaneous GSI, despite some spawning. Based on the condition indexes and time of gonad maturation, the Goheung shrimp population is suitable for use as breeding stock.

• Journal of Aquaculture
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• v.20 no.4
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• pp.278-288
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• 2007

Shrimp culture in Korea had been rapidly developed during 1990's and the production of farmed shrimp reached 3,268 mt from 2,605 ha in 2001. However the shrimp production decreased to 2,368 mt in 2004 because of the mass mortality due to outbreak of white spot syndrome virus (WSSV). WSSV which is one of the most serious threats associated with cultured shrimp around the world has given the economic damages to shrimp culture industry every year since it was found from the shrimp ponds in the west coast of the South Korea in 1993. Various polyculture technologies of shrimp with shellfish, finfish or seaweeds have been implemented to reduce economic damages by mass mortalities of shrimp. Among them, the polyculture of shrimp with carnivorous fish can suppress or delay the viral outbreak of shrimp ponds because the fish may selectively eat the moribund shrimps infected by virus. To determine the selective predatory effect of river puffer Takifugu obscures on WSSV infected shrimp, postlarvae of Litopenaeus vannamei and Fenneropenaeus chinensis. One-year old river puffers were stocked to four earthen ponds of $1,616-1,848\;m^2$ in surface area as followings: polyculture LvP, L. vannamei ($43.4/m^2$)+puffer ($0.22/m^2$); control Lv, L. vannamei ($46.9/m^2$); polyculture FcP, F. chinensis ($30.3/m^2$)+puffer ($0.25/m^2$); control Fc, F. chinensis ($24.6/m^2$). Ponds of control Fc and polyculture FcP had mass mortalities by WSSV outbreak on the $51^{st}$ and $57^{th}$ days of culture respectively. The shrimps of polyculture LvP and control Lv were harvested on the $95^{th}\;day$. Shrimp survival rates of polyculture LvP and control Lv were 32.4% and 18.2% respectively and shrimp productivity of polyculture LvP was 69.2% higher than that of control Lv. Concentration of nutrients (TAN, $NO_2-N$, $NO_3-N$) was maintained within optimal ranges for shrimp growth although that of polyculture ponds showed at least two times higher than that of control ponds. The results suggest that polyculture of L. vannamei with river puffer is higher than monoculture in survival rate and productivity. In addition, F. chinensis should be carefully cultured because this species shows much higher susceptibility to WSSV than L. vannamei.

• Journal of fish pathology
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• v.33 no.1
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• pp.77-81
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• 2020

This study was performed for screening yellow head virus(YHV) complex in 252 including 235 white leg shrimps (Litopenaeus vannamei) and 17 oriental shrimp (Fenneropenaeus chinensis) collected from 18 farms located in southwestern province of Korea. The virus complex was detected by nested reverse-transcriptase polymerase chain reaction (RT-PCR) assay. In the assay, amplicons were resulted in RNAs exracted from 38 shrimps (21 white leg shrimps and 17 oriental shrimps) obtained from 7 farms. In phylogenetic analysis using sequences of ORF1b gene, all 38 sequences obtained in this study formed an independent lineage with YHV-8 genotype firstly isolated in China, belonged to an YHV-8 clade.

• Journal of fish pathology
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• v.19 no.3
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• pp.207-214
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• 2006

Diagnostic monitoring in fish farms with land-based tanks and net cases was conducted in eastern, western, southern and Jeju island of Korea for the summer period from 2000 to 2006. Total 3,518-fish samples of marine and freshwater fishes in 25 fish species were tested for pathogens. Fish species tested were olive flounder (Paralichthys olivaceus), fleshy prawn (Fenneropenaeus chinensis Osbeck), black rockfish (Sebastes schlegeli), rock bream (Oplegnathus fasciatus), red sea bream (Pagrus major), black seabream (Acanthopagrus schlegeli), sea bass (Lateolabrax japinicus), gray mullet (Mugil cephalus), rainbow trout (Onchorhynchus mykiss) and others. The infection rates by bacterial pathogens in the years of 2000, 2001, 2002, 2003, 2004, 2005 and 2006 were 22.4%, 34.5%, 14.1%, 15.3%, 17.7%, 13.5% and 5%, respectively. The infection rates by parasitic pathogens were 20%, 33.8%, 12.4%, 14.1%, 9.2%, 10.5% and 10.7%, respectively. The infection rates by viral pathogens were 22.4%, 13.5%, 10.3%, 5.4%, 9.7%, 10.2% and 15.8%, respectively. The infection rates by mixed pathogens were 10.3%, 0%, 44.9%, 50.9%, 31.9%, 38.4% and 39.6%, respectively. The rates of mixed infections were very low until 2001. The rates were higher than those of singer infections from 2002 to 2006. During the diagnostic monitoring from 2000 to 2006, the main bacterial pathogens were Vibrio (41.2%) and Streptococcus (28.8%). The infection rate by protozoa (85.7%) mainly including Scuticociliates and Trichodina was highest. The infection rate by viral necrosis virus (VNNV, 42.2%) was the highest of the viral pathogens.

• Journal of Aquaculture
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• v.21 no.4
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• pp.339-345
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• 2008

Farming of the fleshy shrimp Fenneropenaeus chinensis which is a major cultured species in the west coast of South Korea, has been suffered :trom mass mortality due to disease epizootics including viruses. Since the Pacific white shrimp Litopenaeus vannamei was introduced to Korea in 2003, farming of this species has rapidly increased for years, occupying 62.5% of total cultured shrimp production in 2007. However the studies on L. vannamei culture methods for shrimp farming situations in Korea are very limited. Nursery culture of shrimp larvae has some advantages including increased survival, improved feed efficiencies, enhanced growth performance and reduced grow-out period. In this study, L. vannamei postlarvae (${PL_3}-{PL_{10}}$) with a density of $3,750-9,090/m^3$ were cultured in four raceways under limited water exchange condition for 35 days. Survival was the highest (93.6%) in tank stocked with $4,090/m^3$ and was the lowest in tank with $9,090/m^3$ (58.1 %). Mean body weight at harvest ranged from 0.071 to 0.108 g, and FCR was 0.59-0.70 in all tanks. Concentration of total ammonia nitrogen was increased up to 20 ppm on day 10 in all tanks and thereafter gradually decreased by the third week of culture. Nitrite-nitrogen was rapidly increased from the third week, representing bio-floc condition by developed nitrifying bacterial community. Of the present nursery system some modification of structure and consideration for commercial scale are needed in order to be implemented to shrimp farmers.