• Korean Journal of Fisheries and Aquatic Sciences
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• v.52 no.2
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• pp.159-172
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• 2019

This study investigated the effects of dietary monobasic potassium phosphate (MKP) on the growth of the far eastern catfish Silurus asotus and four leafy vegetables in a hybrid biofloc technology aquaponic system. To an experimental diet containing 45% protein and 7% lipid, 1, 2, 3 or 4% MKP was added and was designated as MKP1, MKP2, MKP3, and MKP4, respectively. The optimum MKP levels were determined for the growth of fish and four leafy vegetables over 10 weeks. After the 10-week feeding trial, weight gain, feed efficiency, specific growth rate and protein efficiency ratio were higher in the fish groups fed MKP2 and MKP3 than in the other groups (P<0.05). The growth of the four leafy vegetables was also higher in the fish groups fed MKP2 and MKP3. Water quality [dissolved oxygen, pH, water temperature, electrical conductivity, turbidity, total ammonia nitrogen (TAN), $NO_2-N$, $NO_3-N$ and $PO_4-P$] was measured six times a week using a portable water quality meter and reagent measurements. The TAN (4.58-20.40 mg/L), $NO_3-N$ (24.12-52.40 mg/L) and $PO_4-P$ (20.38-48.48 mg/L) levels increased with time, while the $NO_2-N$ level remained below 0.1 mg/L throughout the study.

• Journal of fish pathology
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• v.8 no.1
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• pp.47-55
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• 1995

Classification of peripheral leucocytes in Korean catfish (Silurus asotus) were performed. The leucocytes were classified on the basis of their morphological, cytochemieal and phagocytic characteristics. Four types of leucocytes were observed in the peripheral blood. Neutrophils were round and 12 - $15{\mu}m$ in diameter with round, oval or 2 - 3 segmented neuclei. Their cytoplam was stained whitish or grey. Lymphocytes were round and 5.5 - $8{\mu}m$ in diameter with large round neuclei which occupied most of the cells. Monocytes were round or irregular cells and 12 - $15{\mu}m$ in diameter with bean - shaped or irreular neuclei. Thrombocytes were oval or spindle - shaped cells with oval or spindle - neucle. The cells with greyish cytoplasm ranged 7.2 to $14.4{\mu}m$ in length and 5.8 to $7.2{\mu}m$ in width. Only neutrophils showed positive reaction in peroxidase and PAS. Neutrophils and monocytes showed active phagocytosis. As the results it is concluded that peripheral leucocytes of Koran catfish could be classified as lymphocytes, neutrophils, monocytes and thrombocytes.

• Korean Journal of Veterinary Service
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• v.35 no.4
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• pp.347-350
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• 2012

L-theanine was examined for its effects on the generation of superoxide anion, lysozyme and anti-protease in the plasma of catfish (Silurus asotus) by a single intraperitoneal injection with five different concentrations (0, 3, 6, 9 and 12 mg/kg). When compared with the mock-injected group (0 mg/kg), both groups injected with 6 and 9 mg/kg were significantly enhanced in levels of superoxide anion in leukocytes, lysozyme and anti-protease in plasma. Based on the results, L-theanine is thought to function as an immunostimulant and/or immunomodulator on non-specific immune responses in catfish.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.45 no.2
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• pp.139-145
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• 2012

Two feeding trials were conducted to evaluate the effects of experimental extruded pellets (EEPs) and commercial EPs (CEPs) on Far Eastern catfish $Silurus$ $asotus$ in pilot- (experiment I) and commercial-scale (experiment II) tanks. Four diets were prepared: three EEPs (EEP1, EEP2 and EEP3) that contained different amounts of tuna fish meal, soybean meal, and squid liver oil, and one CEP diet. In experiment I, three replicate groups of juveniles were fed one of the four EPs in pilot-scale tanks for 19 weeks. The weight gains (WGs) of fish fed EEP1 and CEP were significantly higher than those of fish fed EEP2 or EEP3. The highest feed efficiency (FE) was observed in fish fed the CEP diet ($P$<0.05), and the FE of fish fed EEP1 and EEP3 were significantly higher than that with EEP2 ($P$<0.05). In experiment II, juveniles were fed one of four EPs in commercial-scale tanks for 19 weeks. WG and FE values of fish fed EEP1 and CEP were higher than those of fish fed EEP2 and EEP3. The results of this study indicate that the dietary formulation used in EEP1 could be used as a practical feed for Far Eastern catfish.

• Development and Reproduction
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• v.22 no.2
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• pp.165-174
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• 2018

The aim of study is to contribute to this knowledge-base by investigating the respiratory function, the metabolic rate and the difference of physiological responses un-der low water temperature ($20^{\circ}C{\rightarrow}15^{\circ}C$) stress be-tween diploid and triploid far eastern catfish, Silurus asotus. During the 48 hrs of water temperature stress exposure time, the respiratory frequencies, $CO_2$ and ${NH_4}^+$ concentrations of diploid had higher values than those of triploid (p<0.05). However, pH of triploid was higher than those of diploid (p<0.05), and oxygen consumption rate was not different between diploid and triploid (p>0.05). The level of plasma cortisol and plasma glucose of triploid was lower than those of the diploid (p<0.05). However, in case of lactic acid, there were not significant between triploid and diploid (p>0.05). These results suggest that diploid was more sensitive for low water temperature stress response than triploid in this species.

• Journal of Aquaculture
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• v.9 no.3
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• pp.205-213
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• 1996

Experiments were carried out to investigate the effect of GnRH-analogue (GnRH-a) on the induction of ovulation in catfish, S. asotus. Fully matured female catfish ($250\~600\;g$) received a single intraperitoneal injection of GnRH-a ($50\~200\;{\mu}g/kg{\cdot}body$ weight) showed the successful induction of ovulation. More than $86\%$ of treated females were ovulated after injection of GnRH-a ($90\;{\mu}g/kg$) at $25{\pm}1^{\circ}C$. The majority of spawning took place within 22 to 25 hours after the injection. The gonadosomatic index (GSI) and pseudo-GSI in the group treated with $120\;{\mu}g/kg$ GnRH-a were $23-30\%$ and $18-21\%$, respectively. Average fertilization and hatching rates were $94\%\;and\;81\%$, respectively. Electron microscopically, gonadotrophs of maturing female catfish were characterized by the presence of numerous small, electron-dense granules of approximately $150\~300$ nm in diameter and a few larger, less electron-dense granules of approximately $800\~1000$ nm in size in their cytoplasm. Gonadotrophs of GnRH-a treated catfish showed that their was a distinct decrease in number of small and large granules. The rough endoplasmic reticulum was composed of numerous cisternae conspicuosly dilated to various degrees.

• Asian-Australasian Journal of Animal Sciences
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• v.17 no.8
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• pp.1053-1061
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• 2004

Of the 20 arbitrarily chosen primers, six oligonucleotides decamer primers were used on the basis of the number of the polymorphisms generated in catfish (Silurus asotus) from Yesan and bullhead (Pseudobagrus fulvidraco) from Dangjin in Korea. Six primers were used generating a total of 602 scorable bands in catfish and 195 in bullhead population, respectively, ranging in size of DNA fragments from less than approximately 100 to larger than 2,000 base pairs (bp). Six primers yielded 199 polymorphic fragments (33.1%) in catfish and 47 (24%) in bullhead, respectively. In the present study, a total of 328 common fragments (an average of 54.7 per primer) were observed in catfish population, whereas 84 (an average of 14.0 per primer) in bullhead. The total number of specific fragments in catfish and bullhead population were 76 and 64, respectively. In catfish population, random decamer, OPA-17 (GACCGCTTGT) generated the highest number of fragments (a total of 141) in comparison with other primers used, with an average of 11.8. The common bands in the molecular weight of 300 bp generated by random primer OPA-06 (GGTCCCTGAC) were present in every individuals in bullhead population. The major polymorphic bands in the molecular weight of 100 bp generated by OPA-17 were identified in lane 14, 15, 17, 18, 19 20 and 21, which were identifying species in bullhead population. The average bandsharing values (BS values) of all of the samples within catfish population ranged from 0.575 to 0.945, whereas 0.063-1.000 within bullhead population. The bandsharing value (index of similarity between individuals) between individual No. 5 and No. 9 showed the highest level within catfish population, whereas the bandsharing value between individual No. 1 and No. 2 showed the lowest level. The single linkage cluster analysis resulted from four primers, indicating four genetic groupings composed of group 1 (C1-C10, all of the catfish samples), group 2 (B11, B12, B13, B14, B16, B17, B18, B19), group 3 (B15) and group 4 (B20 and B21). The dendrogram reveals close relationships between individual identities within two species populations and individuals derived from the same ancestor, respectively. However, genetic distances between two species populations ranged from 0.124 to 0.333. The shortest genetic distance (0.042) displaying significant molecular differences was between individual No. 6 and No. 9 catfish population. The shortest genetic distance (0.033) displaying significant molecular differences also was between individual No. 18 and No. 19 in bullhead population. Reversely, the genetic distance of individual No. 20/21 among individuals in bullhead population was highest (0.333). This result showed that bullhead No. 20 and 21 were distinct from other individuals within bullhead population.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.43 no.5
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• pp.445-450
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• 2010

This study investigated the effects of dietary lipid sources on growth performance and body composition of juvenile far eastern catfish, Silurus asotus. Three replicate groups of fish (average weight 3.6 g) were fed with one of the following experimental diets containing 10% beef tallow (BT), 5% BT plus 5% corn oil (CO), 5% BT plus 5% linseed oil (LO), or 5% BT plus 5% squid liver oil (SO) as the lipid source for 5 weeks. No significant difference was observed in the survival among groups. The weight gain of fish fed the LO (high in 18:3n-3) and SO (high in n-3 highly unsaturated fatty acid) diets was significantly higher than that of the fish fed the CO (high in 18:2n-6) and BT diets (P<0.05). The feed efficiency of fish fed LO and SO diets was significantly higher than that of the fish fed the BT diet (P<0.05), but not significantly different from that of the fish fed the CO diet. The protein efficiency ratio of fish fed the SO diet was significantly higher than that of fish fed the CO and BT diets (P<0.05), but not significantly different from that of fish fed the LO diet. The 18:1n-9 of whole-body polar lipid fraction in fish fed the BT diet increased compared to that of fish fed the other diets. Fish fed the CO and LO diets had significantly higher contents of 18:2n-6 and 20:4n-6, and 18:3n-3, than the fish fed the other diets in polar and non-polar lipid fractions, respectively (P<0.05). Significantly higher contents of 20:5n-3 and 22:6n-3 were observed in the whole-body polar lipid fraction of fish fed the SO diet compared with fish fed the other diets (P<0.05). The study results indicate that linseed oil and squid liver oil containing n-3 fatty acids are good dietary lipid sources for the growth of far eastern catfish.

• Journal of fish pathology
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• v.6 no.1
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• pp.1-10
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• 1993

Two vibrio sp. strains were isolated from disease catfish(silurus asotus). The present isolates were identified as Vibrio ordalii based on their biological and biochemical characteristics ; they were positive for acid production from glucose, Iactose, maltose, sucrose and salicine, while negative for arabinose, galactose, inocitol and xylose. They are named KL-1 and KL-2, KL-1 and KL-2 strains were similar to physiological characteristics ; growth was observed at pH 5 to 10 and in 0% to 6.0% NaCl. Two strains did not growth at a concentration above 7.0% NaCl and pH10. This bacterium was infected into health catfish hypodermically. Such injection was found to induce haemorrhagic ulcers very similar to those observed in naturally infected fish. At 24h post-infection, the red spot developed around the injection site and grew bigger to from a red sport area. At 120h post-infection, the muscle ncerosis was extended near the ventral fin. The seventy percent lethal dosage was appeared to water temperature at $25^{\circ}C$. Two strains were tested for drug senistiveity by plate method. KL-1 and KL-2 strains were sensitive to GM. K, N, S and SxT, but resistant to CF, L and VA.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.1
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• pp.56-61
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• 1999

Oxygen consumption rate of Far eastern catfish, Silurus asotus, weighing 280g, was measured using continuous flow respirometry chamber linked computer monitoring system. Mean oxygen consumption rates at $15^{\circ}C,\;20^{\circ}C,\;25^{\circ}C$, and $30^{\circ}C$ were ranged in 35.2$\~96.4mg\;O_2/kg$ fish/hr, 78.6$\~127.9mg\;O_2/kg$ fish/hr, 120.1$\~231.7mg\;O_2/kg$ fish/hr, and 197.5$\~352.3mg\;O_2/kg$ fish/hr, respectively. The oxygen consumption rates increased with increasing water temperature (p<0.05). A photoperiod-mediated oxygen consumption rates was higher during the light period than during the darkness (P<0.05). When acclimated with different photoperiods, 24L:0D, 12L:12D, and 0L:24D, the lowest oxygen consumption rate was observed in the continuous darkness (0L:24D). The differences between maximum and minimum oxygen consumption rates oyer 24 hour increased with increasing water temperature and the difference was the highest in 12L:12D. Oxygen consumption rate changed suddenly at dawn and at dusk.