• Parasites, Hosts and Diseases
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• v.49 no.2
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• pp.161-165
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• 2011

The present study was performed to determine the current infecion status of Metagonimus yokogawai metacercariae in sweetfish, Plecoglossus altivelis, collected from several streams in eastern and southern coastal areas of Korea. The sweetfish collected were artificially digested with pepsin-HCI solution and examined under a stereomicroscope in August and September, 2007. Out of 145 sweetfish collected from 10 streams in eastern coasts (Gangwon-do and Gyeongsangbuk-do), 88 (60.7%) were infected with Metagonimus metacercariae. The average metacercarial density was 61 per infected fish. Among 141 sweetfish collected from 10 streams in southern coasts (Gyeongsangnam-do, Ulsan Metropolitan city, and Jeollanam-do), 140 (99.3%) were infected with Metagonimus metacercariae, and their average density was 949 per infected fish. The present study confirmed that M. yokogawai metacercariae are still prevalent in the sweetfish from several eastern and southern coastal localities. The prevalence and metacercarial density were much higher in the sweetfish from streams of southern coasts than in those of eastern coasts. Therefore, attention should be paid to this small fluke infection, and consumption of raw sweetfish naturally produced in these areas should be prohibited.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.37 no.1
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• pp.7-12
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• 2004

This study investigated the possibility of salinity acclimation of freshwater rotifers (Brachionus calyciflorus) as live food for sweetfish (Plecoglossus altivelis) larvae, and also examined the optimal salinity for the growth of sweetfish. Freshwater rotifers cultured in 0 and 4 PSU and seawater rotifers (B. rotundiformis) cultured in 33 PSU were supplied to the larvae with four kinds of enrichment material (condensed freshwater Chlorella, $\omega-yeast,$ baker's yeast, Super Selco) and larval growth at 4 PSU was examined. Growth of the freshwater rotifers positively increased from 0 PSU to 6 PSU, but decreased when over 8 PSU was reached. Growth and survival of the sweet fish larvae reared in 0 PSU were significantly lower than those reared in either 4 PSU or 33 PSU. This indicated that the freshwater rotifers (B. calyciflorus) could be used as live food for sweetfish larvae reared in 4 PSU. The body weight of sweetfish larvae fed on freshwater rotifers enriched with Super Selco was the highest at 0.163 mg, but there was no significant difference in survival and body length of the fish fed with the other enrichment materials. The content of n-3 HUFA of the sweetfish larvae fed on the freshwater rotifers enriched with Super Selco and the condensed freshwater Chlorella was higher than that enriched with $\omega-yeast$ and baker's yeast. These results indicated that B. calyciflorus cultured with the condensed freshwater Chlorella could be used for the sweetfish larvae without enrichment, and the most efficient enrichment material for B. calyciflorus is Super Selco.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.26 no.3
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• pp.235-240
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• 1993

This study was carried out to compare the difference of proximate composition and total lipid components by size and various tissues in sweetfish(Plecoglossus altivelis). Lipid contents of the small and large sweetfish in viscera were $43.2\%\;and\;52.8\%$, respectively. Total lipid contents of the small and large sweetfish were consisted of $3.84{\sim}46.90g/100g$ neutral lipid, $0.86{\sim}4.38g/100g$ phospholipid, respectively. In fatty acid compositions of total lipid, sweetfish showed higher content in saturates such as 16:0, 18:0($43.78{\sim}48.29\%$), and lower content in polyenes such as 18:2n-6, 22:6n-3($13.13{\sim}17.10\%$), and the large sweetfish was somewhat higher in ratio of polyenes compared with the small one. The major fatty acids were 16:0, 18:1n-9, 16:1n-7, 18:2n-6, 22:6n-3, 18:0 and 14:0, in order.

• Journal of the Korean Society of Food Science and Nutrition
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• v.39 no.6
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• pp.853-858
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• 2010

The purpose of the study was to determine fat contents and fatty acid compositions of the lipids in sweetfish cultured in Korea and lipid oxidation during storage at refrigeration temperature ($2^{\circ}C$). Whole or minced sweetfish were vacuum-packaged or treated with ascorbic acid. Changes in thiobarbituric acid (TBA) values, peroxide values (PV) and free fatty acid (FFA) in the fish were determined. Sweetfish contained 72.5% moisture, 5.3% lipid and 1.1% ash. Palmitic acid was the highest (27.4% (w/w) of the total fatty acids) among the saturated fatty acids. Total monounsaturated fatty acids (MUFA) were 33.9% and oleic acid (21.0%) was the highest, followed by palmitoleic acid (7.8%). Total PUFA were 28.2%. Predominant PUFA were linoleic acid (8.1%), EPA (5.7%) and DHA (12.1%). TBA values and PV of the whole sweetfish treated with ascorbic acid and vacuumpackaged were not different from the control. TBA values of the minced sweetfish treated with ascorbic acid were significantly lower than the other groups (p<0.05). PV of the fish treated with ascorbic acid and vacuum packaging were significantly lower than the other groups (p<0.05). The result of this study suggests that cultured Korean sweetfish may be a good source of unsaturated fatty acids including EPA and DHA, and vacuum packaging and addition of ascorbic acid may protect lipids from oxidation.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.40 no.4
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• pp.183-186
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• 2007

The effect of live food and commercial diet on sweetfish Plecoglossus altivelis culture was assessed by determining the daily growth rate and feed conversion ratio. After feeding for 8 weeks, the Moina macrocopa diet resulted in a higher growth rate of 5.101 compared to commercial (3.441) and Artemia (2.729) diets. In addition fish fed the M. macrocopa diet had the weight gain, averaging 41.29 g at the end of the experiment. The content of n-3 highly unsaturated fatty acids (HUFA) was highest in the commercial diet, while free fatty acids were not detected in the M. macrocopa diet. Triglycerides, the energy source in fishes, constituted 40.0% of the M. macrocopa diet, which was significantly higher than in the commercial and Artemia diets at 20.0 and 12.0%, respectively These results indicate that freshwater M. macrocopa can be used as feed for sweetfish larvae, even without docosahexaenoic acid (DHA) enrichment from Artemia.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.6
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• pp.565-571
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• 2000

Mixed primers based on the high sequence homology of selected regions of known connexins (Cxs) was used for PCR reaction. A full-length connexin cDNA of sweetfish (Plecoglossus altivelis) was cloned by rapid amplification of cDNA 5'and (5'RACE) and 3'RACE method. When compared to other known Cx sequences, homology of sweetfish Cx cDNA to Atlantic croaker, Mycropogonias undulatus Cx32.7, bovine, Bos taurus Cx44 and Atlantic croaker Cx32.2 were $63.8{\%},\;61.6{\%}\;and\;56.7{\%}$, respectively. This cDNA encoded 308 amino acids (35,028 dalton) and named as sweetfish Cx35. Hydropathicity analysis of predicted amino acid sequences indicated that sweetfish Cx35 have four major hydrophobic regions and four major hydrophilic regions, suggesting its topology is similar to that of known Cxs. The presence of a tfical Cx consensus sequences were identified in each of the extracellular loops (first loop and second loop).

• Journal of Korea Water Resources Association
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• v.34 no.4
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• pp.381-390
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• 2001

This is to evaluate the ascending capacity of migratory fish in the pool and weir type fishways. Ascending environment of the migratory fish in rivers is analyzed through eco-hydraulic experiments using sweetfish, Plecoglossus altivelis, trout, Oncorhnchus mykiss, and surveying the fall height of existing pool and weir type fishways. When the fall height is less than 16.0cm, the ascending capacity of sweetfish in the pool and weir type fishways is greater than trout. On the other hand when the fall height is over 20.0 cm, the ascending capacity of trout is greater than sweetfish. A sweetfish may prefer to jump for upward moving than trout. And its endurance after upward jumping over wear is greater than that of sweetfish. Because of high fall height of existing pool and weir type fishways the migratory environment in rivers is so poor. When the pool and weir type fishways are designed and constructed in river the fall height of weir must be considered for the variety of migratory fish living in river and the fall height of weir less than 20.0cm is suggested.

• Journal of Aquaculture
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• v.7 no.3
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• pp.135-150
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• 1994

For the effective seedling production of the sweetfish, Plecoglossus altivelis, dietary value of live food in the growth and survival rate of the larvae was examined. To investigate dietary value of three types of rotifers (L-type, S-type, Us-type rotifer) for the sweetfish larvae, the larvae were fed with alone or mixed with each type and with mixtures of two or three types. Although the survival rates of the larvae fed different types of rotifers were not significantly different among them, the larvae fed a mixture of three types of rotifers showed the highest growth significantly. A feeding trial was conducted to determine the effect of the dietary values of rotifer and Artemia nauplius enriched with Chlorella ellipsoidea, $\omega-yeast$, spray-dried Spirulina platensis, and Super Selco for the sweetfish larvae. The dietary values of rotifer and Artemia nauplius enriched with Super Selco mixed with spray-dried S. platens is were distinctly improved for the survival rate and growth of the larvae. With regard to effect of the green water with Chlorella ellipsoidea, spray-dried Spirulina platensis, and the addition of photosynthetic bacteria (Rhodopseudomonas capsulatus), the green water with Spirulina platens is mixed with photosynthetic bacteria also enhanced the growth and survival rate of the larvae.

• Parasites, Hosts and Diseases
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• v.28 no.4
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• pp.253-256
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• 1990

This study was performed to observe the infection status of sweetfish, caught from Kwangjung- stream and Namdae-stream in Yangyang-gun, Kangwon-do in August 1989, with the metacercariae of Metagonimus yokogawai. All of 28 sweetish from Kwangjung-stream were infected with the metacercariae of M. yokogawai. The number of metacercariae in a fish ranked 89-521(224 on average), and the number of larvae/g of mesh was 12-55(22 on average). On the other hand, no metacercariae were detected in the fish from Namdae-stream. It has been confirmed that the Kwangjung-stream in Yangyang-gun, Kangwon·do is one of the endemic foci of metagonimiasis in Korea.

• Journal of Aquaculture
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• v.12 no.2
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• pp.123-135
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• 1999

In order to investigate the effect of salinity on growth and osmoregulation of the sweetfish, Plecoglossus altivelis, the fish (post-larva, juvenile, adult) reared in seawater were directly transferred into the experimental rearing water of the different salinities (post-larva : $0\textperthousand$, $5\textperthousand$, $10\textperthousand$, $15\textperthousand$, $20\textperthousand$, $30\textperthousand$. juvenile : $0\textperthousand$, $\10textperthousand$, $20\textperthousand$, $30\textperthousand$. adult : $0\textperthousand$, $15\textperthousand$, $35\textperthousand$, respectively). Fish samples were taken in time courses after transfer for blood and body fluid collection. The changes of sodium, potassium concentration and osmolality of the body fluid and plasma, muscle water content, gonadosomatic index (GSI) and hepatosomatic index (HSI) in the experimental fish were observed in time courses. Growth rate of the post-larva in $\5~25\textperthousand$ were faster than in $0\textperthousand$ (P<0.05). Survival rate was very low in $0\textperthousand$ (P<0.05). No fish survived more than 50 days after transferred into $0\textperthousand$. The concentration of sodium, potassium and osmolality in body fluid of the juvenile sweetfish were slightly decreased at 0.25 day after the beginning of the maintainable level of sodium, potassium and osmolality were $36.4\pm6.2 mM/\ell, 47.5\pm0.7 mM/\ell, 366.3\pm19.1 mOsm/kg, respectively. Except potassium concetration, fish in $0\textperthousand$ and $10\textperthousand$ displayed the pattern of hypoosmotic regulation. Growth rate and survival rate of juveniles of $30\textperthousand$ are significantly low than other groups (P＜0.05). The concentration of sodium, potassium and osmolality in plasma of adult sweetfish were slightly decreased at 1 day after the beginning of the maintainable level of sodium, potassium and osmolality were $159.0\pm2.5 mM/\ell, 5.8\pm0.9 mM/\ell, 338.1$\pm13.3 mOsm/kg respectively. Compared with these values, fish in $0\textperthousand$ and $15\textperthousand$ displayed hypoosmotic regultion. Growth and survival rate of adult in $35\textperthousand$ are significantly low than other experimental groups. GSI was the highest in $15\textperthousand$ after 60 days. HSI was the lowest in $35\textperthousand$. With decreased salinities, oxygen consumption was found to be decreased in the other experimental groups compared to the more than $30\textperthousand$.