• Journal of fish pathology
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• v.10 no.2
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• pp.113-123
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• 1997

Concerned to the life cycle of Ichthyophthirius multifiliis, the biological characteristic of the parasites was studied in the rainbow trout (Oncorhynchus mykiss) and the Korean catfish (Silurus asotus) Under the experimental condition of $9^{\circ}C$- $28^{\circ}C$, tomitogenesis rate was positively proportional to water temperature, but not at over $28^{\circ}C$. The protomonts showed a high rate of tomitogenesis at $26^{\circ}C$ in comparision with other temperature conditions. Temperature affected tomitogenesis rate which resulted from the various conditions of salinity, pH and formalin concentration. The protomonts showed a high rate of tomitogenesis at pH 6.9 in comparision with other pH conditions at all temperatures tested. This result revealed that the opitimum pH for tomitogenesis was 6.9. The protomont had more tolerance against salinity and formalin concentration at low temperature ($18^{\circ}C$) than at high one ($22^{\circ}C$). Both trophont and protomont were not infective, but theront was infective.

• Korean Journal of Ichthyology
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• v.20 no.4
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• pp.239-247
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• 2008

The objective of this investigation was to examine oxygen consumption (OC) and operculum movement number (OMN) of rainbow trout Oncorhynchus mykiss as a function of changes in water temperature (WT). The WT of the rearing facility was increased from $4^{\circ}C$ to $28^{\circ}C$ stepwise at $1^{\circ}C$ day at each WT (5, 10, 15, 17, 20, 23, 26, and $28^{\circ}C$) then OC and OMN were measured. The OC of the fish increased linearly with WT: O=25.0240 WT+17.5400 in the range of $4{\sim}23^{\circ}C$ However, at 26 and $28^{\circ}C$ the OC declined to around the level at $10^{\circ}C$. The OMN also increased linearly with temperature: OMN=4.4847 WT+59.2150 in the range of $4{\sim}23^{\circ}C$ but at 26 and $28^{\circ}C$ the OMN of the fish dropped slightly. The OC and OMN of the fish showed peak at $23^{\circ}C$ with the lowest values at $4^{\circ}C$. In the range of $4{\sim}23^{\circ}C$, the relationship between OC and OMN of the fish was expressed as a linear equation: OC=0.0923 OMN-308.2100. The OC of fish transferred from $15^{\circ}C$ to certain temperatures without acclimation showed a lower OC at 5 and $10^{\circ}C$ but above $15^{\circ}C$ the OC increased/decreased with temperature. The trout died in temperatures above $28^{\circ}C$ even when acclimated step by step with a $1^{\circ}C$ day increase in WT. In this experiment, a negative physiological changs occurred in the experimental fish at $23^{\circ}C$ suggesting that the optimal physiological temperature range of rainbow trout is $10{\sim}20^{\circ}C$.

• Journal of Wetlands Research
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• v.20 no.4
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• pp.398-409
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• 2018

Organic farming practices including loach based ecosystem-farming have been demonstrated to be effective in conjunction with rice farming to increase yield and quality. This new form of farming combines agriculture and fishery and is quickly developing into a new industry. The current study investigated the effect of rice-fish mixed farming system on the vegetation-diversity function. Vegetation within the four study sites was surveyed and analyzed based on plant taxonomy. The vegetation survey demonstrated that 127 taxa of 38 families, 100 genera, 107 species, and 20 varieties occurred within the study sites. A total of 15 plant species taxa occurred in the rice-fish mixed paddy fields with a fish habitat and did not occur in the conventional paddy field lacking fish habitat. This difference is thought to arise from differences in moisture requirements for vegetation. Life form analysis demonstrated differences in hemicryptophytes, therophytes, and hydrophytes according to fish habitat. The naturalized plants identified were also determined to be species widely distributed throughout Korea. Frequency analysis demonstrated that the rice-fish mixed paddy fields with a fish habitat had a high ratio of both obligate and facultative wetland plants relative to the conventional paddy field. Based on the study results, it is likely that vegetation-diversity will increase with environment diversity. However, no statistical significance was observed according to paddy types. Future research should aim to identify additional environmental factors, including the existence of fish habitat, habitat area, depth of fish habitat, hydrological parameters, water quality, and paddy soil environment, to enhance vegetation-diversity and biocultural diversity.

• Journal of Aquaculture
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• v.20 no.3
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• pp.160-167
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• 2007

Embryonic and pre-leptocephalic larvae development of the eel, Anguilla japonica, are described following natural fertilization in the indoor tank of $23^{\circ}C$ water temperature. Following a routine hormone treatment technique for the brood stock, female eels were artificially matured by weekly intramuscular injections of salmon pituitary extracts (SPE) at a dosage of 20 mg/kg body weight (BW) for a total of 10-14 doses to induce ovarian maturation, while male eels received weekly intramuscular injections of human chorionic gonadotropin (HCG) at a dosage of 1 IU/g BW for a total of 6-10 doses to induce testicular maturation in a separate aquarium and induced natural spawning. Fertilized eggs of about 1.0 mm in diameter were pelagic and showed a typical discoidal cleavage. Hatching occurs 38 hrs after fertilization at a water temperature of $23^{\circ}C$. The newly hatched larvae measured about 3.0 mm in total length and the number of myomeres averages 42. Their mouths and anuses were opened at 4.5 days and the yolk sacs of the pre-leptocephalic larvae were almost absorbed at 6.5 days after hatching. Pre-leptocephalic larvae survive for 14.5 days. At this time they are $5.87{\pm}0.25mm$ in total length and have about 98 myomeres. However, morphological characterization of embryonic and pre-leptocephalic larvae were not different between natural fertilization and artificial fertilization by the dry method.

• Fisheries and Aquatic Sciences
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• v.27 no.3
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• pp.145-158
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• 2024

Life history characteristics, habitat landscape, and historical events are believed to have shaped the patterns of genetic variation in many taxa. The bony lip barb, Osteohilus vittatus, represent a potamodromous fish that complete all life cycle in freshwater and is widely distributed in Southeast Asia. It usually lives in small rivers and other freshwater habitats, and movement between habitats for either food or reproduction has been typical. These life history characteristics may promote gene flow, leading to less structured populations. However, many freshwater habitats are fragmented, which restricts gene flow. We investigate how this interplay has shaped patterns of genetic variation and phylogeographic structure within this species in the Sundaland, a biodiversity hotspot with a complex geological history, using mitochondrial cytochrome oxidase I (mtCOI) as a genetic marker. Forty-six mtCOI sequences of 506 bp long were collected from ten localities, eight geographically isolated and two connected. The sequences were used for population genetic and phylogeographic analyses. Our results showed a low genetic diversity within populations but high between populations. There was a deep phylogeographic structure among geographically isolated populations but a lack of such structure in the connected habitats. Among geographically isolated populations, sequence divergence was revealed, ranging from 1.8% between Java and Sumatra populations to 12.2% between Malaysia and Vietnam. An indication of structuring was also observed among localities that are geographically closer but without connectivity. We conclude that despite high dispersal capacity, the joint effects of historical events, long-term geographic isolation associated with sea level oscillation during the Pleistocene, and restricted gene flow related to lack of habitat connectivity have shaped the phylogeographic structure within the O. vittatus over the Sundaland.

• Korean Journal of Ichthyology
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• v.24 no.3
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• pp.160-166
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• 2012

Egg development and early life history of the endangered Korean freshwater fish, Microphysogobio koreensis, was investigated to get a basic information for establishing its conservation strategy. The matured adult fishes were sampled at Imsil-gun, Jeollabuk-do, Korea in May 1 2012 and artificially fertilized. The fertilized eggs were spherical, separated demersal and $1.8{\pm}0.14mm$ in diameter. The hatching of the embryo began at about 29 hours after fertilization under water temperature of $23^{\circ}C$. The newly hatched pre-larvae were average $2.2{\pm}0.48mm$ in total length. At 4 days after hatching, the post-larvae were $3.6{\pm}0.55mm$ in total length and york sac was completely absorbed. At 20 days after hatching, their fin rays were formed and finally the larvae entered juvenile stage and grew up to $6.5{\pm}0.77mm$ in total length. At 60 days after hatching, the total length reached $24.4{\pm}1.71mm$, and the band patterns of he head and lateral side were similar to adult fish. Based on this study, the fertilized eggs of M. koreensis hatched more quickly and the pre-larvae length was also smaller, compared with related species.

• Journal of fish pathology
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• v.3 no.1
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• pp.21-25
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• 1990

In inland aquaculture, a lot of fishes often died cause of touch of L. carteri which is attached on the net cage. In this works, the experiment were carried out on classification of species, toxin test, and extermination with some chemicals. A bryozoa from net cage in lake Okjeong is classified into the Phylactolaemata, Lophopodella carteri Hyatt. A bryozoa broke out firstly on the 30th of June with water temperature up to $31^{\circ}C$ and it reattached on the net with water temperature below $30^{\circ}C$. Size of bryozoa colony is about $0.8{\times}0.6{\sim}1.7{\times}1.5cm$. Water column of attachment was 0~5m and the peak is 2~3m. In toxin test on the israeli carp, goldfish and catfish touched with bryozoa for 1 minute at $25^{\circ}C$ of water temperature, a dead fish appeared at 20 minutes after touched. Mortality was 90% for israeli carp and 100% for goldfish at 100 minuties after touched, but catfish was not died at all. It was supposed that the toxin is from nematocyst being around tentacles and this toxin act a deadly poison on a israeli carp and goldfish. In extermination test, the bryozoa treated with 300ppm of formalin, 5% of sodium chloride, 5ppm of malachite green, 200ppm of potassium permanganate, 1000ppm of potassium iodide, 10ppm of DDVP for minute respectively, all of them were not effected.

• Korean Journal of Ichthyology
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• v.29 no.4
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• pp.235-243
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• 2017

Reproductive characteristics of Rhodeus pseudosericeus (Pisces: Acheilognathinae) was investigated at the Heukcheon (River), Yangpyeong-gun, Gyeonggi-do, Korea from January to July in 2012. This fish prefers heavily vegetated stagnant pool with Phragmites japonica and Salix koreensis and area with high proportions of sand and mud. The standard length of the population indicated that 13~22 mm group is 0-year old, 30~45 mm group is 1-year old, 45~55 mm group is 2-year old and 45~70 mm group is more than 3-year old (June in 2012). The sex ratio of female to male was 1 : 0.80. The spawning season was from March to June with water temperatures in the range $11.0{\sim}26.2^{\circ}C$. The embryos were found with no egg mass in Unio douglasiae sinuolatus and the number of those was 1~22 ($5.8{\pm}5.51$). The number of the embryos found in each of the four parts of the mussel gill was 1~9 ($2.7{\pm}2.16$) in left outer, 1~2 ($1.5{\pm}0.71$) in left outer, 1~5 ($1.8{\pm}1.79$) in left outer and 1~22 ($5.8{\pm}5.51$) in left outer.

• Journal of Marine Life Science
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• v.7 no.2
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• pp.196-204
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• 2022

This study observed changes in survival, growth performance and water quality for 90 days to confirm the possibility of Leiocassis ussuriensis farming using Biofloc technology (BFT) using Bacillus subtilis. Feed and molasses were added to the experimental tank to produce BFT water before planting the experiment, and B. subtilis was inoculated to stabilize the water quality for 40 days. The survival rate of the experimental fish was 92.7±3.2% in the control group and 95.8±3.3% in the BFT group. The Weight gain (WG) was 118.1±9.0% of the control and 197.7±15.6% of the BFT, and the Specific growth rate (SGR) was 0.87±0.5% of the control and 1.21±0.06% of the BFT. As for the feed efficiency, the control was 43.7±2.6% and the BFT was measured at 70.1±4.1%, indicating that the feed efficiency of the BFT was higher. As a result of measuring the water quality change during the experimental period, pH was reduced in both the control and the BFT, and Mixed Liquor Suspended Solids (MLSS) did not show any change in the control, but the BFT showed a significant increase at 90 days. NH₄⁺-N and NO₂^--N showed a significant increase from the 30 days of the experiment in the control, but showed no change in the BFT. In conclusion, as a result of applying the BFT system using B. subtilis to the process of cultivating Leiocassis ussuriensis, the water quality tended to stabilize, and the growth rate and feed efficiency were found to be higher than those of the control, confirmiWng that it had a positive effect.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.57 no.2
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• pp.177-185
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• 2024

We developed a regional ocean climate model using dynamic downscaling in the Northwest Pacific Ocean to build a climate model for the Korean Peninsula. The past marine environment was reproduced through historical simulations, and the future marine environment in 2100 was predicted according to the shared socioeconomic pathways (SSP) climate change scenario. The future sea surface temperature of the Korean seas is predicted to rise about 1-4℃, and the increase in water temperature in the East Sea is expected to be the largest. The National Institute of Fisheries Science has monitored abnormal seawater temperatures such as high and low seawater temperatures in coastal and inland waters, and predicted that the number of high seawater temperature days in the East, West, South Sea, and the coast of Jeju Island will increase in the future. In addition, the occurrence of Ciguatera fish poison plankton around Jeju Island was projected to increase. This study is expected to provide accurate forecasting information for fishery issues. The aim of this study was to analyze future ocean environment changes around the Korean Peninsula using climate change SSP scenarios and predict fisheries issues through future projections of the regional ocean climate model.