• Development and Reproduction
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• v.4 no.2
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• pp.147-152
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• 2000

Four clonal lines of ayu, Plecoglossus altivelis, were produced through gynogenesis, mixed before hatching and reared communally. After 10 months, a randomly taken sample was subjected to a standardized shallow water stressor. Hematocrit, hemoglobin, red blood cells count (RBC) and mean corpuscular volume (MCV) were obtained from stressed and non-stressed fish. DNA fingerprinting was used to confirm the clonal nature of the organisms and to identified the clonal line to which each fish belonged. 1 observed significant differences between clona] lines mostly in the hematocrit and MCV measured under no-stress conditions. Such differences are suggested to represent mainly genetic variance, on account of the common environment provided to all the experimental groups. The stress response ratio was lower than expected, mainly due to some unexpectedly high non-stress values. Heritability values (h$^2$) were medium to high for the no-stress measurements (mean 0.238) and very low or zero for the stressed groups'traits (excepting one high value of 0.484). 1 conclude that the use of communally reared clonal lines represents a good tool for the characterization of the physiological traits, thus allowing for their utilization as genetic selection criteria.

• Korean Journal of Veterinary Research
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• v.38 no.2
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• pp.371-378
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• 1998

Five strains of gram-negative and yellow-pigmented bacteria were recently isolated from diseased freshwater fishes in Korea. All isolates were confirmed as a known fish pathogen of columnaris disease, Cytophaga columnaris based on their colonial and cellular morphology, and on physiological, biochemical and antigenic characteristics. Although the isolates were from different fish species, their characteristics of them were very similar to those of the reference strains of C columnaris (NCMB $2248^T$ and EK 28). Also, profiles of OMPs of Korean isolates were similar to those of the reference strain, C columnaris NCMB $2248^T$ when analyzed by SDS-PAGE.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2001.05a
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• pp.319-321
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• 2001

Supply of ntrition-balanced feed is very important for growth of fish, especially for growth of early period of fish. Therefore, most of commercial feeds for larval and juvenile fish are relatively expensive due to high level of the several nutrients to satisfy their requirements for growth. Overfeeding larval fish may increase fish production cost because of larvae feeds high price and deteriorate water quality, eventually reduce growth of fish. (omitted)

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.1
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• pp.32-37
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• 2001

Fabrea salina is an euryhaline ciliate living at salt pond. Its size is small as ca. $150{\mu}m$, and its reproductive rate is high, so that this ciliate has been expected to be a new food organism which will be able to replace rotifer, Brachionus plicatilis. However, the dietary value of F. salina on fish larvae has not yet been verified thoroughly. This research was carried out to understand the mass culture technique and dietary value of this ciliate. In this study, six kinds of phytoplankton and three kinds of grain were tested on growth of the ciliate and optimum temperature, salinity and density of food were also examined for its mass culture. Regarding food for the ciliate, Heterosigma sp. and rice showed the highest growth among the phytoplankton and the grain, respectively. In this study, 229 ciliates per mL was cultured with Heterosigma sp., and 220 ciliates per mL with rice. The optimum temperature for F. salina was $33^{\circ}C$, and salinity ranging from 35 to 95 ppt had no significant difference on its growth. The optimum food density and amount for the ciliate were $5\times10^6$ cells/mL in Heterosigma sp. and 2.8 g/L in rice, respectively. With respect to dietary value of F. salina, six-day-old larvae of ayu, Plecoglossus altivelis, fed on the ciliate showed the high mortality over $96\%$ within 3 days, and it was significantly higher than those fed on rotifer. Even though the mass culture of F. salina has been achieved in the study, this ciliate seems to be inadequate as a food organism for fish larvae.

• Journal of fish pathology
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• v.9 no.1
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• pp.11-13
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• 1996

Ergasilus sieboldi, a parasitic Copepoda, was detected from the gill of Silurus asotus fingerling(7~10 cm long) cultured at a fish farm in Chungnam Province (Fig. 1 and 2). The infected fish did not show any particular external symptoms except a feeble swimming around the boarder of the pond. The isolated parasite was of 1.07 mm in body length with two egg sacks of 1.05 mm and one pair of hook-shaped secondary tentacle. Bychowsky(1963) described that this parasite infected the gill of Salmonidae, Serranidae, Cyprinidae and Siluridae and that the fish in the Baltic Sea, Black Sea. Caspian Sea. Japanese sea zones, Siberian rivers and Lake Bikal were infectd. Bychowsky further pointed out that heavily infected fish with this parasite become emaciated and slow in growth. and often die. As this parasite infected on the peri-branchial area. the infected fish showed a severe disturbance of respiration. Urawa et ai.(1980) studied on the development of Neoergasilus japonicus. an Ergasilidae, which infects Japanese freshwater fish. In Korea, Chun(1985) reported the identification of Ergasilus sieboldi from imported carp. and Neoergasilus and Pseudogasilus japonicus from bluegills. respectively. Chun also identified Pseudoergasilus zacconis in cultured ayu(Plecoglossus altivelis). However. this report deals with the detection of Ergasilus sieboldi from cultured catfish(Silurus asotus) for the first time in Korea.