• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.56 no.5
• /
• pp.634-643
• /
• 2023

The effects of dietary supplementation with fermented blood meal (FBM) in two forms were evaluated on the growth performance, hematological parameters, innate immune response, antioxidant capacity, digestive enzyme activity and intestinal histology of Japanese eel Anguilla japonica. A commercial powder feed was used as a basal diet (Con). Six other diets were prepared by supplementing 2, 4 and 6% FBM either in powder or liquid form to the Con diet (designated as P2, P4, P6, L2, L4 and L6, respectively). In total 420 eels (initial mean body weight: 55.1±1.71 g) were distributed into 21 tanks (450L) at a density of 20 eels per tank. Three replicate groups of fish were fed one of the seven diets twice daily for 12 weeks. No significant differences were observed in the growth performance and survival among all groups. Fish fed FBM-containing diets showed significantly improved hematological parameters, innate immunity and antioxidant capacity than those in the Con group. Fish fed FBM-containing diets showed significantly enhanced digestive enzyme activity, villus length and goblet cells than those in fish fed Con diet. These results indicate that both powder and liquid FBM could be a good functional feed additive to improve innate immunity and digestion in Japanese eel.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.48 no.1
• /
• pp.44-50
• /
• 2015

The basic and main nutritive ingredients of two temperature (Anguilla japonica and A. rostrata) and two tropical (A. bicolor pacifica and A. marmorata) fresh water eel species that are farmed domestically were evaluated. With exception of A. rostrata, eels cultured at the same farm were used for analysis. The contents of crude protein were in the order A. marmorata (17.7%)>A. rostrata (17.5%)>A. bicolor pacifica (17.4%)>A. japonica (15.8%) and the contents of crude lipids were A. japonica (21.5%)>A. rostrata (15.4%)>A. bicolor pacifica (10.5%)>A. marmorata (8.9%). These values differed significantly even among the three species of eel farmed under identical culture conditions. In comparison, all four species of eel showed similar pattern in overall amino acid composition, although slight differences in the compositions of some amino acids were observed. The fatty acid compositions of muscle tissues were notably different among four species of eel, especially between the tropical and temperature eels. In a taste-test of the meat of the four eel species, which considered taste, flavor and texture, the overall preference was in the order A. japonica, A. marmorata, A. bicolor pacifica and A. rostrata.

• Development and Reproduction
• /
• v.12 no.3
• /
• pp.261-266
• /
• 2008

In the present study, we investigated in vivo effects of Manchurian trout recombinant gonadotrophin hormone (mt-rGTH) on the induction of maturation in female eel, Anguilla japonica. The brood stock, female eel (450$\pm$50 g) were weekly injected intramuscularly with different doses of 0.1, 1, 10 ${\mu}g\m{\ell}$/fish (mt-rFSH or mt-rLH) for 10 week. The effects of r-mtGTH were analyzed by gonadosomatic index (GSI), ovarian follicle diameter and sex steroid levels. All groups did not exhibit significant differences in the GSI values. Whereas plasma testosterone (T) and estradiol-17$\beta$ (E2) levels did not change significantly in control group, plasma levels of T and E2 by injection of the r-mtFSH or r-mtLH were increased at 2 or 4 week after injection. In addition, injection of the mt-rFSH (1, 10 ${\mu}g/m{\ell}$/fish) or mt-rLH (0.1, 1, 10 ${\mu}g/m{\ell}$/fish) significantly increased follicle diameters comparing to the control group. These results demonstrate that the recombinant hormone may affect early ovary development and maturation in female eel. Taken together, these results suggest that the recombinant Manchurian trout FSH and LH are effective for reproductive activities in female eel.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.27 no.5
• /
• pp.454-461
• /
• 1994

This studies was carried out in order to investigate the browning reaction of lipid originated compound with nitrogenous compound in dried conger eel. The major fatty acids were $C_{16:0},\;C_{16:1},\;C_{18:1},\;C_{20:5}\;and\;C_{22:6}$. The nonpolar lipid contained the highest percentage of $C_{16:0}$, while the polar lipid contained the highest percentage of $C_{22:6}$. The browning reaction there was a rapidly developed with the beginning of the decline in carbonyl value and remarkable decrease in polyunsaturated fatty acids such as $C_{20:5},\;C_{22:5},\;C_{22:6}$ compared with the other fatty acid, in the water soluble fraction of the browning product obtained from tile fish was detected some antioxidation activity but in the lipid soluble fraction which covers most of the browning reactions in the fish meat antioxidation activity was not detected. In the test of conger eel oil, the phosphatidylcholine was largest in quantity and browning products provided in this experiment showed very low reducing activity.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.50 no.1
• /
• pp.58-66
• /
• 2014

The purpose of the study is to estimate the Green-House-Gas (GHG) emissions from domestic eel farm in the water recirculation system or still-water system by the assessment of energy consumptions and GHG emissions for establishing to reduce standards of GHG from a sustainable perspective. GHG emission components as seeds, feed, fuel, electricity, fixed capital, fish respiration, and others were analysed at the different culture type between water recirculation system and still-water system by 3 stage farm size of small, medium, large scale. The result showed that the mean GHG emission of the eel farm was $18.7kg{\cdot}CO_2$ in the stage of production per fish 1kg at different culture type and farm size. Therefore it could be useful for policy, planning, and regulation of aquaculture development with establishing GHG reduction standards.

• Journal of fish pathology
• /
• v.36 no.2
• /
• pp.239-250
• /
• 2023

Disease monitoring was conducted to investigate the recent disease occurrence in Japanese eels (Anguilla japonica). Between May 2021 and March 2022, an investigation was conducted on eels from seven farms experiencing mortality. JEECV (Japanese eel endothelial cells-infecting virus) was detected in all examined farms, each exhibiting co-infections with 1 or 2 bacteria, including Edwardsiella anguillarum, E. piscisida, Aeromonas sp., Citrobacter freundii, Lactococcus garviae, or Vibrio sp. From March 2022 to October 2023, monthly periodic inspections were carried out at a farm in Yeonggwang, Jeollanam-do, for a total of 22 times. JEECV was detected in 10 out of 22 times, even when mortality was not recorded. Bacteria such as E. anguillarum, C. freundii, Aeromonas sp., and Vibrio sp. were isolated, but consistent clinical signs of liver abscess and hemorrhagic lesions were only recognized in fish infected with E. anguillarum. Other bacteria were often isolated from apparently healthy fish. In conclusion, mortality in eel farms frequently occurs due to co-infections of JEECV with bacteria rather than JEECV alone. Therefore, to reduce eel mortality, it is crucial to decrease co-infections, with a particular emphasis of JEECV and E. anguillarum.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.41 no.1
• /
• pp.1-6
• /
• 2008

The changes in osmolality and the gene expression profiles of prolactin (PRL) and growth hormone (GH) with rapid changes in salinity were compared in the eel (Anguilla japonica), crucian carp (Carassius carassius), and masu salmon (Oncorhynchus masou). Fish stocked in freshwater (FW) were abruptly transferred to experimental tanks containing FW, 50% seawater (50% SW), or 100% SW (SW). Blood samples and pituitary glands were collected 2 and 24 hrs after the exposure. No mortality was observed in SW eel (n=6), whereas all of the crucian carp (n=6) and two masu salmon (n=6) exposed to SW died after land 24 hrs, respectively. The PRL mRNA levels of the eel and masu salmon decreased in 50% SW and SW compared to those of the fish kept in FW after 24 hrs, whereas the PRL levels of crucian carp were higher in 50% SW than in FW. Unlike the PRL mRNA levels, the GH mRNA levels of the eel did not differ significantly among three different salinities, while the GH mRNA levels of crucian carp and masu salmon increased significantly in 50% SW and SW after 24 hrs. The serum osmolalities increased marginally in the eel and masu salmon in 50% SW at 24 hrs (19% and 9%, respectively), whereas those of crucian carp increased abruptly in 50% SW (50% increase). These results suggest that the synthesis of PRL and GH is important in relation to the osmoregulatory system with environmental changes in salinity.

• Korean Journal of Food Science and Technology
• /
• v.19 no.1
• /
• pp.1-4
• /
• 1987

A seasonal variations of chemical components and gel forming ability in wild common carp (Cyprinus car-pio) and conger eel (Astroconger myriaster) caught around Pusan, Korea monthly for one year (from May,1984 to April, 1985) were investigated. During a year variation range in the moisture and crude lipid contents were found in conger eel meat showing 61.0-76.6% and 5.4-20.8%, while crude protein, ash and carbohydrate were no appreciable differences . Ail of the moisture of chemical components were nearly constant in wild common carp for 12 months. The contents of moisture were less, while crude lipid were more in conger eel meat from September to February than those of the other months. Qualities of the fish jelly were the best for that months in conger eel. Fish jellies were good for 12 months in wild common carp. Gel forming ability was related to the content of chemical components and fishing season in conger eel.

• Applied Biological Chemistry
• /
• v.39 no.2
• /
• pp.134-139
• /
• 1996

In order to effectively utilize marine animal skin wastes in marine processing manufacture, conger eel skin, file fish skin and arrow squid skin as raw material of edible gelatin were screened. Conger eel skin was the highest in the collagen content, followed by Ole fish skin and arrow squid skin, in the order named. In the fish skins, the soluble and insoluble collagens occupied $67.4%{\sim}72.3%\;and\;27.7{\sim}32.6%$, respectively, and in the arrow squid skin, 30.4ft and 69.6ft, respectively. No difference in the amino acid composition between soluble and insoluble collagens was detected. Collagen from the marine animal skin catched in coasted and offshore water in Korea consisted ${\alpha}$ chain and ${\beta}$ chain, and ${\alpha}$ chain were hetero type. The sum of proline and hydroxyproline contents in conger eel skin collagen was higher than that in the other skin collagens, while was lower than that pork skin collagen. Conger eel skin collagen exhibited a higher denaturation temperature in solution and a higher degree of proline hydroxylation, compared with skin collagen of the respective species. The physical properties such as gel strength, melting point and gelling point of conger eel skin gelatin were superior to those of file fish skin and arrow squid skin gelatins.

• Journal of Fisheries and Marine Sciences Education
• /
• v.18 no.3
• /
• pp.374-378
• /
• 2006

Eel is Anguilla japonica and Anguillidae family as a freshwater fish, and Japanese name is Unagi. The content of vitamin A of eel muscle are about 4,000IU/100g and they have many effective components, so it is known as healthy food. Therefore, many people have eel that cooked roast and hot-water extract in Korea. WHO encouraged that daily edible content of vitamin A is 2,000IU. Now, Japan government proposes the weight of roasted eel in lunch basket as 50g. But, Korea government does not proposes in every related aspects. Therefore, we researched content of vitamin A in hot-water extract from eel and optimal processing condition of hot-water extract from eel, in order to determine a proper edible volume. The content of vitamin A in eel hot-water extract sold at a market was about 200 IU. This study resulted from the fact that many eel hot-water extracts lacked the vitamin A. The reason was that the lipids were removed for taste on processing. But, The content of vitamin A in eel hot-water extract which didn't removed lipid on processing was about 800IU. Therefore, in drinking for 3packs per day, eel hot-water extract might have adjusted 100mL per pack which is almost consistent with the recommended dietary allowance of vitamin A in WHO.