• Fisheries and Aquatic Sciences
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• v.16 no.2
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• pp.85-92
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• 2013

To determine the relative importance of two main factors, diet or culture environment, that affect the proximate composition and main nutritive ingredients (vitamin A, vitamin E, cholesterol, fatty acid composition) in cultured eels, we analyzed the composition of eels fed diets of formula feed (FF) produced by four different companies and of eels cultured at five different eel farms that provided only one of the four different FFs. The four commercial eel FFs did not markedly differ in proximate composition or major nutritive compounds, and consequently, these variables did not significantly differ in cultured eels fed the different FFs. The FF imported from Japan was marginally superior to the two domestic commercial FFs and the FF imported from Taiwan in terms of the proximate composition and main nutritive ingredients of both the FF itself and the eels cultured on it. However, proximate composition and main nutritive ingredients significantly differed among eels cultured at the five farms that used a different FF and among eels fed the four different FFs at the same farm. In conclusion, the difference in quality between domestic and Japanese FFs in terms of eel culture was small, whereas physical or chemical environmental differences among farms during eel culture may more strongly affect the proximate composition and levels of the main nutritive ingredients in cultured eels.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.44 no.3
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• pp.237-242
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• 2011

To evaluate the proximate composition and main nutritive ingredients (vitamin A, $V_A$; vitamin E, $V_E$; cholesterol; the composition of fatty acids) between eels cultured in different domestic eel farms, we analyzed edible parts of eels that were cultured in three "Water Recirculation System (WRS)" farms and three "Still-Water System (SWS)" farms. We found differences in crude protein, crude lipids and the ash content of eel meat between the farms, but water content showed no significant difference. $V_A$ and $V_E$ contents did not show meaningful differences between the two culture methods, but there was a noticeable distinction between the eel farms. In particular, $V_E$ content showed significant differences between the eels of each farm (highest farm, about 25 mg/100 g dry wt; lowest farm, about 1 mg/100 g dry wt). The fatty acids of cultured eels were composed of monoenes (MUFA, 55-60%), saturates (SFA, 30-33%), $\omega$-6 highly unsaturates (HUFA, 1.6-2%) and $\omega$-3 HUFA (8-9.2%). The MUFA content of WRS eels ($59.9{\pm}1.97%$) was higher than that of SWS eels ($55.8{\pm}0.48%$). The contents of other fatty acids were higher in SWS eels (SFA, $33.0{\pm}0.52%$; $\omega$-6FUFA, $1.98{\pm}0.2%$; $\omega$-3 HUFA, $9.2{\pm}0.67%$) than in WRS eels (SFA, $30.5{\pm}1.34%$; $\omega$-6 HUFA, $1.62{\pm}0.19%$; $\omega$-3 HUFA, $8.0{\pm}0.5%$).

• Journal of fish pathology
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• v.20 no.3
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• pp.291-297
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• 2007

The effect of aspirin on the recovery of nitrite-induced methemoglobinemia in cultured eels (Anguilla japonica) was studied. Methemoglobinemia was induced by exposing eels to nitrite (120 ㎎ NO2-N/ℓ) for 24 hr. The nitrite exposed eels were bathed in 20 ppm aspirin solution (Aspirin), 0.8 % NaCl solution (NaCl), 20 ppm aspirin plus 0.8% NaCl solution (NaCl + Aspirin) and 50% nitrite free water(control) for 24 hr to recover from nitrite toxicity. Peripheral blood was taken from the arterious bulb from all groups to analyse hematocrit value, hemoglobin concentration, and nitrite concentration of the blood. Histopathological features of gill were also observed. Aspirin and control groups were more effective than NaCl and NaCl + Aspirin groups in recovery of hematocrit value and hemoglobin concentration, methemoglobin rate and nitrite concentration. The histopathological features on the gill of aspirin group were similar to those of normal eels, but other groups showed focal hyperemia in the lamellar carpillaries, epithelial hyperplasia. These results suggested that aspirin was very effective to recover from methemoglobinemia in nitrite-induced cultured eels.

• Korean Journal of Veterinary Research
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• v.50 no.1
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• pp.29-35
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• 2010

Yersinia (Y.) ruckeri has been recognized as a serious bacterial pathogen to several kinds of fish, including rainbow trout. However, there are no reports about the characteristics and pathogenicity of Y. ruckeri isolated from farm-cultured eels. In this study, we isolated and characterized Y. ruckeri from the farm-cultured eel Anguilla japonica in Korea. We investigated the phenotypic and genotypic characteristics of Y. ruckeri and tested the virulence of Y. ruckeri isolates on experimentally infected eels. Examination of the flagellar morphology of Y. ruckeri by electron microscopy showed peritrichous flagella in its cell body. Biochemical reaction studies showed overall identical profiles between the isolates and the reference strain of Y. ruckeri in API 20E and API ZYM tests. We sequenced the 16S rRNA of the Y. ruckeri (1,505 bp) for the genotypic characterization (National Center for Biotechnology Information accession number EU401667). Comparison of the 16S rRNA sequences with previously reported Y. ruckeri strains revealed similar phylogenetic relationships. In the virulence assay of the Y. ruckeri on eels, the eels exhibited listlessness, but Y. ruckeri was reisolated from those of the gills and kidneys.

• Journal of fish pathology
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• v.21 no.3
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• pp.229-239
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• 2008

The aim of this study was to acquire level on the occurrence of five fluoroquinolones(FQs) residue among cultured eels in Jeonbuk province. Samples were collected from the four local area(Kunsan, Gochang, Wanju and Osu) and surveyed on the distribution of FQs residual level in edible muscle using HPLC method. A total of 90 samples of eel was monitored for detection of the FQs residue. Among them, 30 eels(33.3%) were detected the FQs single or paired, respectively. The detection ratios were showed Osu(40%, 8/20), Gochang(33%, 13/44), Wanju(30%, 6/20) and Kunsan(30%, 3/10) in order, respectively. The ratio was equivalent to over 30% of overall in sampled area. The most frequently detected FQs were perfloxacin(PF) followed by enrofloxacin(EF), ciprofloxacin(CF), ofloxacin(OF) and norfloxacin(NF). Eight different combinations of FQ residual patterns were observed as single(5 type, 21%) or as paired(3type, 12,5%) respectively and frequently encountered patterns were PF(37%) and PF-EF(23%). The residual level of FQs was evaluated in the range of 1-75 ug/kg and the most prevalent levels of FQs was found in 1-25 ug/kg(35 fish, 85%) followed by 26-50 ug/kg(5 fishes, 11%) and 51-75 ug/kg(1 fishes, 3.3%). These results could be possible that the cultured eels were mostly exposed with PF, EF and CF, and might be treated with a variety of fluoroquinolones for prevention of bacterial disease.

• Journal of fish pathology
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• v.8 no.2
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• pp.111-118
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• 1995

This experiment was carried out in order to elucidate the effect of NaCl(0.85%) acclimation on congestion symptoms in central venous sinuses(CVS) of gill filaments and on the alteration of blood constituents in cultured eels for 1, 2, 3, 4, 5, 6 and 7days after handling stress. After giving a handling stress on eels, the frequency of gill congestion was about 90%. It gradually decreased to 40% on the 3rd day, then increased to 60% on the 7th day in NaCl(0.85%) acclimation. The values of haematocrit(Ht), methemoglobin(Met-Hb), glucose (GLU), calcium($Ca^{++}$), lactic dehydrogenase(LDH), glutamic pyruvic transaminase (GPT) and glutamic oxaloacetic transaminase(GOT) were lower than those of the control, whereas magnesium($Mg^{++}$) and haemoglobin(Hb) were higher than the control. However total protein(Tp) and albumin (ALB) levels similar to the control. When the fish after giving a handling stress were cultured in NaCl-free water as a control, the frequency of gill congestion and the value of blood components showed a similar pattern to that obtained from the NaCl acclimated experiments. However, in the early period(1-3day) after handling stress, NaCl acclimating slightly helped the natural tendancy of recovery. These results suggest that the frequency of gill congestion is not always reduced over the whole period of NaCl acclimation. However, the acclimation to NaCl solution may be a somewhat useful therapy for the gill congestion in stressed eels.

• Journal of Aquaculture
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• v.16 no.4
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• pp.267-272
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• 2003

This study investigated sex determination through serum steroid hormone level and compared hematological characteristics of one-year old cultured eels, Anguilla japonica. Four different groups were divided with total length at 40∼45, 45∼50, 50∼55, and 55∼60 cm. Males dominated eels of 40∼50 cm in total length group, while females dominated eels of more than 50 cm. All females and males were immature. Hematocrit levels of males (total length: 40∼50 cm) were higher than those of females (total length: 50∼60 cm). Hemoglobin content also differed between males and females. Glutamate oxaloacetate transaminase (GOT) levels of 40∼45 cm males tended to be higher (157$\pm$3.46 IU/L) than that of other sized males, but there were no significant differences between groups (P<0.05). The highest GOT levels were found in of 55∼60 cm females (148$\pm$3.46 IU/L) compared with that of other female groups (P<0.05). Glutamate pyruvate transaminase (GPT) levels of males and females in the 55∼60 cm size range was significantly higher thanothers (P<0.05). The result of this study indicated steroid hormone content of males and females were very low, but testosterone (T) and estradiol-17$\beta$, (E2) contents of females were higher than those of males. For further research of sex determination in cultured eels, it needs to investigate in more defined body length.

• Korean Journal of Microbiology
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• v.22 no.1
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• pp.41-48
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• 1984

Twenty two cultures of pathogenic bacteria were isolated from cultured eels(Anguilla japonica) from Asan Hatchery. The bateria were characterized by their biochemical properties, serological relationships, infectivity to gold fish and susceptibility to various antimicrobial compounds. Fourteen of 22(64%) cultures were identified as Edwardsiella tarda, five (23%) as Aeromonas hydrophila and three (14%) as Vibro anguillarum. Edwardisiella tardo isolates proved to be the main cause of the disease in cultured eels. They were serologically homogeneous and their virulency to gold fish was higher than any of the other groups of bacteria tested. The virulence of 3 isolates were low in gold fish exposed to the bacteria by the waterborn route. Ten strains were tested for their susceptibility to 12 antimicrobial compounds and were resistant to from one to six drugs: in particular, tetracycline derivatives and sulfisoxazole.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.39 no.6
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• pp.466-471
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• 2006

We investigated the changes in body weight (BW), plasma sex steroid hormone profiles, and testicular development of cultured male eel Anguilla japonica during an artificial maturation process. Eels that received weekly intraperitoneal injections of eel's ringer solution containing human chronic gonadotropin (HCG) were examined. In the ringer-treated control, BW changes decreased slowly during the experimental period. Plasma testosterone (T), 11-ketotestosterone (11-KT) and $17{\alpha},\;20{\beta}$-dihydroxy-4-pregnen-3-one (DHP) levels In the control remained low and did not show significant changes. Moreover, all germ cells in the testes of the control were spermatogonia. In the HCG-treated male eels, however, BW changes increased gradually from the fifth week and then decreased slowly. The plasma T level increased rapidly (p<0.05) in the second week and then decreased slowly. The plasma 11-KT level increased dramatically (p<0.05) in the second week and was maintained until the end of the experiment. The plasma DHP level increased progressively from the second week and peaked in the eighth week (p<0.05). The testes of HCG-treated male eels were more developed than those of the control; most were at the spermatozoa and spermatid stages and showed active spermiation. Thus, spermatogenesis and spermiation in the cultured eel can be induced by repeated injections of HCG.

• Journal of fish pathology
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• v.7 no.2
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• pp.161-171
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• 1994

In order to elucidate the outbreak mechanisms of a new disease which is characterized by an intense congestion in central venus sinuses(CVS) of gill filaments in cultured eel. these experiments were carried out; epidemically surveyed on the cultured eel farms in the vicinity of Kunsan city and experimentaliy outbreaked the disease in the stressful condition such as thermal and handling shock and innoculated the supernatant from the homogenate of naturally severe congested gill into eels and onto the monolayer of the CHSE-214. Although the frequency of congestion in eels of B, C, D and E farms were higher than in eels of A farms, the water qualities(stocked and cultured water) among farms were not a great difference. In eels of B, C, D and E farms, the values of haematocrit(Ht), haemoglobin(Hb), total protein(Tp), albumin(Alb), glucose(Glu), magnesium(Mg) were lower and the values of calcium(Ca), methemoglobin(Met-Hb), glutamic pyruvic transminase(GPT), glutamic oxalacetic transminase(GOT) higher than in eels of A farms. These valules have not related to the frequency of congestion. An intensive congestion and dilataton in CVS of gill filaments in experimentally handling-stressed eels produced similar histopathological changes to those observed in the spontaneously diseased eel, but not in eels experimentally injected with filtering contents. The cytopathic effect on the CHSE-214 was not observed. In stressed eels the congestion of gill was increased in relation to either the decrease ranges of water temperature or the incerase in accllimated times. And increase in Ht, Met-Hb, Alb, Glu, GOT and GPT and decrease in Mg, Hb and Tp were found, which had a close relationship to congestion of gill. Cortisol were increased according to the decrease ranges in acclimated water temperature. From these results, decrease in water temperature during selection placed eels upon the stressed condition, made increase in ionic strength in blood stream, and CVS was dilatated owing to the increased blood inflow.