• Korean Journal of Fisheries and Aquatic Sciences
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• v.56 no.2
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• pp.188-195
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• 2023

Antimicrobial resistance patterns of Escherichia coli strains isolated from 30 seawater samples and 30 Korean rockfish Sebastes schlegelii collected from fish farms off the South Coast of Korea in 2018-2019, were investigated. The isolated E. coli (154 strains) showed the highest antimicrobial resistance to tetracycline (44.8%) followed by chloramphenicol (38.3%), streptomycin (37.6%), and trimethoprim/sulfamethoxazole (35.7%). The antimicrobial resistance rate was higher in E. coli strains isolated from Korean rockfish than those from seawater. Multiple antibiotic resistance (MAR) against at least three antimicrobials (MAR index: ≥0.2) was observed in 35.6% and 79.2% of the seawater and Korean rockfish isolates, respectively. In conclusion, continuous monitoring is required to identify changes in antimicrobial resistance and their correlations in the aquatic environment and products.

• Journal of fish pathology
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• v.23 no.1
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• pp.119-122
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• 2010

Mortality and gill lesions in snakehead, Channa argus (body length range, 20.3-22.2 cm) reared in a aqua-farm in Busan, Korea, were associated with a dense bloom of Apiosoma-like ciliate, Order Petrichida. The size of parasite was $48.83{\pm}7.75{\mu}m{\times}14.29{\pm}2.66{\mu}m$. Histological examination revealed that a severe edema and collapse of the gill tissue were observed in a number of samples of snakehead. The mechanism of gill damage was likely due to physical irritation by the parasite. It is believed that this is the first report of Apiosoma-like ciliate in cultured fish in Korea.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.56 no.4
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• pp.373-379
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• 2023

The dietary inclusion of black soldier fly larvae meal Hermetia illucens (BSL) for starry flounder Platichthys stellatus was examined in a four-month trial at a Pohang fish farm. Two diets were prepared: a fish meal-based commercial diet (CD) and an experimental diet containing 7% BSL in the CD (BCD). Fish (average weight, 125.2 g) were reared in a square concrete tank (7×7 m) in triplicates. Feed efficiency was significantly higher in fish fed BCD compared to that of the fish fed CD. The DHA/EPA ratio in dorsal muscle was not significantly affected by the fatty acid composition of the experimental diets. Based on the growth performance, the feed cost for producing 1 kg of starry flounder was 1,797 won for CD and 1,814 won for BCD. With government subsidies the feed cost for producing 1 kg of starry flounder was 1,481 won for CD and 1,309 won for BCD. The results indicate that BSL can be included at 7% without adverse effects on growth performance, fillet composition, or feed cost. However, further research is needed to determine the optimum percentage of BSL as a replacement of FM in starry flounder diets.

• Fisheries and Aquatic Sciences
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• v.20 no.8
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• pp.16.1-16.8
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• 2017

The exportation of cultured olive flounder (Paralichthys olivaceus) in Korea has been recently decreasing due to the infections with a myxozoan parasite Kudoa septempunctata, and there is a strong demand for strict food safety management because the food poisoning associated with consumption of raw olive flounder harbouring K. septempunctata has been frequently reported in Japan. The life cycle and infection dynamics of K. septempunctata in aquatic environment are currently unknown, which hamper establishment of effective control methods. We investigated sea water and marine invertebrates collected from olive flounder farms for detecting K. septempunctata by DNA-based analysis, to elucidate infection dynamics of K. septempunctata in aquaculture farms. In addition, live marine polychaetes were collected and maintained in well plates to find any possible actinosporean state of K. septempunctata. The level of K. septempunctata DNA in rearing water fluctuated during the sampling period but the DNA was not detected in summer (June-July in farm A and August in farm B). K. septempunctata DNA was also detected in the polychaetes Naineris laevigata intestinal samples, showing decreased pattern of 40 to 0%. No actinosporean stage of K. septempunctata was observed in the polychaetes by microscopy. The absence of K. septempunctata DNA in rearing water of fish farm and the polychaetes N. laevigata intestinal samples during late spring and early summer indicate that the infection may not occur during this period. N. laevigata was suspected as the possible alternate invertebrate host of K. septempunctata, but the actinosporean stage was not found by well plate method and further studies will be necessary. This research provides important baseline information for understanding the infection dynamics of K. septempunctata in olive flounder farms and further establishment of control strategies.

• Fisheries and Aquatic Sciences
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• v.23 no.8
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• pp.22.1-22.8
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• 2020

Background: High demand and low supply of fishmeal due to overexploitation of fisheries resources have resulted in a dramatic increase in the price of this ingredient. Olive flounder (Paralichthys olivaceus) commercial feed contains approximately 60% fishmeal and limited success has been achieved in identifying sustainable alternative protein sources for this species. Methods: An on-farm feeding trial was conducted to compare a basal diet containing 65% as the control (CONT) with two experimental diets replacing 10% of fishmeal by animal protein (AP₁₀) or 20% of fishmeal by animal and plant protein (APP₂₀). Sub-adult olive flounder averaging 327 ± 9.3 g (mean±SD) were fed one of the three diets in triplicate groups for 16 weeks. Results: Weight gain, specific growth rate, feed efficiency, protein efficiency ratio, and survival were not significantly different among fish fed all the experimental diets (P > 0.05). Also, non-specific immune responses (superoxide dismutase and lysozyme activity), serum biochemical parameters, and intestinal villi length were not significantly different among fish fed all the experimental diets (P > 0.05). Conclusions: Therefore, based on growth performance, non-specific immune responses, serum biochemical parameters, and intestinal histology, dietary animal and plant protein mixtures could replace up to 20% of fishmeal in the diet of sub-adult olive flounder.

• Fisheries and Aquatic Sciences
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• v.23 no.5
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• pp.13.1-13.7
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• 2020

Stock enhancement is considered to be a valuable approach for restoring fishery resources. Because no specific official institution in Taiwan is responsible for the production of fry, the released fry are purchased directly from the private sector. However, fishermen from the private industry have not established a genetic background, so the genetic composition for each batch of released fry is unclear. Mangrove red snapper (Lutjanus argentimaculatus), a prominent species released in Taiwan, was collected after its official release. One hundred and two field samples were compared with four batches of hatchery fry (n = 685) by using a microsatellite-based multiplex PCR assay. Four of the field samples (3.9%; 4/102) were revealed to be from a fish farm and most likely from a single batch. This study revealed that wild mangrove red snappers are genetically different from those originating from farms, and their origins can be traced through molecular markers, even without information on breeding stocks.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.43 no.2
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• pp.125-130
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• 2010

A trimethoprim resistant Vibrio parahaemolyticus, which cause acute gastroenteritis in humans, was isolated from farmed fish and seawater. The resistance profiles of isolated V. parahaemolyticus and their correlation with mobile elements were investigated. All of the V. parahaemolyticus were resistance to both rifampin and trimethoprim. The presence of class I integron was confirmed by PCR. PCR-amplified inserted gene cassettes contained aminoglycoside aac6-II, rifampin arr-3 and trimethoprim dfrA27 resistance genes. This study indicated that class I integron mainly contributed to the circulation of trimethoprim resistance determinants in V. parahaemolyticus.

• Journal of fish pathology
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• v.22 no.2
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• pp.107-113
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• 2009

Catfish Silurus asotus sampled from a pond farm in Korea, was affected with an epithelial tumor resembling catfish Ameiurus nrbulosus lip and mouth epithelioma. The neoplasm appeared in the form of solitary, multiple, large and fleshy masses upon the skin, fin or barbel. The epithelial tumor proliferation causes papillary folds supported by connective tissue cords. These folds extended above the normal skin surface and into the underlying dermis. In some area, proliferation of mucous cells or club cells were observed. The epithelial cells of the tumor were dispersed with no orderly arrangement. This is the first report on epithelioma of catfish in Korea.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.6
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• pp.699-705
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• 1999

The effects of iron on gill tissue and metabolic rate represented by oxygen consumption of olive flounder, Paralichthys olivaceus were determined. The effects were further studied by means of survival rate of the fish exposed to a serial concentrations of iron. The olive flounder exposed to iron concentrations over 0.93 mg/$\ell$ showed curvature and terminal clubbing of gill lamellae at 2 weeks post-exposure. In iron concentration 4.89 mg/$\ell$, gill of the fish were seriously damaged just after 2 weeks, showing hyperplasia of filament epithelia, deformation of lamella epithelia, chloride cell damage, and separation of lamella epithelial layer, Gills exposed to 9.78 mg/$\ell$ iron concentration resulted in fusion and necrosis of the lamellae after 2 weeks. Significant decreases of metabolic rate of the fish were observed after 4 weeks at iron concentration 0,93 mg/$\ell$ and after 2 weeks at iron concentrations over 4.89 mg/$\ell$. Survival rate of the olive flounder decreased significantly after 4 weeks at the iron concentration over 4.89 mg/$\ell$. These results lead us to conclude that, as far as the iron effects are concerned, its concentrations should not exceed at least more than 0.93 mg/$\ell$ in the fish farm and coastal waters for normal growth of the olive flounder.

• Fisheries and Aquatic Sciences
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• v.21 no.2
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• pp.6.1-6.10
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• 2018

The intention of this study was to identify the bacterial pathogens infecting Oreochromis niloticus (Nile tilapia) and Clarias gariepinus (African catfish), and to establish the antibiotic susceptibility of fish bacteria in Uganda. A total of 288 fish samples from 40 fish farms (ponds, cages, and tanks) and 8 wild water sites were aseptically collected and bacteria isolated from the head kidney, liver, brain and spleen. The isolates were identified by their morphological characteristics, conventional biochemical tests and Analytical Profile Index test kits. Antibiotic susceptibility of selected bacteria was determined by the Kirby-Bauer disc diffusion method. The following well-known fish pathogens were identified at a farm prevalence of; Aeromonas hydrophila (43.8%), Aeromonas sobria (20.8%), Edwardsiella tarda (8.3%), Flavobacterium spp. (4.2%) and Streptococcus spp. (6.3%). Other bacteria with varying significance as fish pathogens were also identified including Plesiomonas shigelloides (25.0%), Chryseobacterium indoligenes (12.5%), Pseudomonas fluorescens (10.4%), Pseudomonas aeruginosa (4.2%), Pseudomonas stutzeri (2.1%), Vibrio cholerae (10.4%), Proteus spp. (6.3%), Citrobacter spp. (4.2%), Klebsiella spp. (4.2%) Serratia marcescens (4.2%), Burkholderia cepacia (2.1%), Comamonas testosteroni (8.3%) and Ralstonia picketti (2.1%). Aeromonas spp., Edwardsiella tarda and Streptococcus spp. were commonly isolated from diseased fish. Aeromonas spp. (n = 82) and Plesiomonas shigelloides (n = 73) were evaluated for antibiotic susceptibility. All isolates tested were susceptible to at-least ten (10) of the fourteen antibiotics evaluated. High levels of resistance were however expressed by all isolates to penicillin, oxacillin and ampicillin. This observed resistance is most probably intrinsic to those bacteria, suggesting minimal levels of acquired antibiotic resistance in fish bacteria from the study area. To our knowledge, this is the first study to establish the occurrence of several bacteria species infecting fish; and to determine antibiotic susceptibility of fish bacteria in Uganda. The current study provides baseline information for future reference and fish disease management in the country.