• Journal of fish pathology
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• v.16 no.1
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• pp.23-30
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• 2003

On September in 1998, a microsporidian infection was recognized in ayu, Plecoglossus altivelis, farmed on Kyongnam province of South Korea. Cumulative mortality was around 10% in 10 days. Infected fish which were piping for air near the surface of the water or in the asphyxic, lethargic condition revealed darkening of body and abdominal distention. Numerous whitish nodules up to 3mm in size were observed throughout most of body organs and tissues including gill, operculum, peritoneal wall and organs. Xenomas were also histologically confirmed in multiple internal organs with the evidences suggesting circulatory disturbance. Based on the morphology of spore and xenoma, and the distribution of xenomas in organs and tissues, this disease was diagnosed to be a microsporidiosis caused by Glugea plecoglossi. The mortality might be deeply related to the local circulatory disturbance by xemonas rather than the mechano-chemical effect of xenomas on adjacent tissues.

• Korean Journal of Ichthyology
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• v.19 no.2
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• pp.142-153
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• 2007

Fertilized eggs of Plecoglossus altivelis over than 1,000,000 were introduced into Okjeong, Jeollabuk-do, Korea by K-water, 2001. Since then, this lake and the neighbouring tributaries gave sufficient habitat to maintain their life cycle which are being the land-locked. A land-locked ayu of annual life is ascending and descending from Lake Okjeong to streams for spawning and growth. Among the streams, the Churyeong stream reaching about 32 km in length is a major site for growth and spawning. But the land-locked ayu was no longer seen in the upper regions of the Churyeong stream over than about 12 km distance from Lake Okjeong. Because there were 11 weirs along with the Churyeong stream, it was difficult for them to move freely up to upper regions, and it causes irregular growth condition although they must be actively growing with feeding for spawning. During three survey years (2004 to 2006), in lowest rainfall-recorded 2005, the ayu population was not able to move up actively across the weirs and just stayed around the weirs, and finally it let them grow slowly and unstably. Also although there are 11 weirs, only 3 fish ways existed. Such environmental factors will seriously affect growth, spawning and size of ayu population in this area.

• Animal Systematics, Evolution and Diversity
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• v.28 no.4
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• pp.279-290
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• 2012

Plecoglossus altivelis (ayu) is an amphidromous fish widely distributed in Northeastern Asia from the East China Sea to the northern Japanese coastal waters, encompassing the Korean Peninsula within its range. The shore lines of northeastern region in Asia have severely fluctuated following glaciations in the Quaternary. In the present study, we investigate the population genetic structure and historical demographic change of P. altivelis at a population level in East Asia. Analysis of molecular variance (AMOVA) based on 244 mitochondrial control region DNA sequences clearly showed that as the sampling scope extended to a larger geographic area, genetic differentiation began to become significant, particularly among Northeastern populations. A series of hierarchical AMOVA could detect the genetic relationship of three closely located islands between Korea and Japan that might have been tightly connected by the regional Tsushima current. Neutrality and mismatch distribution analyses revealed a strong signature of a recent population expansion of P. altivelis in East Asia, estimated at 126 to 391 thousand years ago during the late Pleistocene. Therefore it suggests that the present population of P. altivelis traces back to its approximate demographic change long before the last glacial maximum. This contrasts our a priori expectation that the most recent glacial event might have the most crucial effect on the present day demography of marine organisms through bottleneck and subsequent increase of effective population size in this region.

• Korean Journal of Ichthyology
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• v.19 no.1
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• pp.24-34
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• 2007

After releasing more than 1,000,000 fertilized eggs of Plecoglossus altivelis into Lake Okjeong, Jeollabuk-do, on October, 2001 by KOWACO, they seem to be land-locked. Study on the distribution and ecology of a land-locked ayu, P. altivelis, was performed from Lake Okjeong to upper streams as Jowon, Churyeong, Oknyedong where consisted of rocky bottom with fast current freshwater system during April to October. The hatched larva and juveniles descended from streams to Lake Okjeong and inhabit Lake Okjeong from November to next March. The sex ratio of female to male was 1 : 2.70, and the size in standard length of females and males was similar, in $90{\sim}220(142{\pm}29.3)mm$. During the middle September to the middle October, they laid eggs on the pebbly bottom of the rapids which are $20{\sim}22^{\circ}C$ in water temperature and 30~70 cm in depth. The number of full-grown eggs was greatly various from 14,283~91,500.

• Korean Journal of Ichthyology
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• v.20 no.3
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• pp.179-189
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• 2008

Standard length (SL) and gonadosomatic index (GSI) of Plecoglossus altivelis were investigated from March to October 2007 in Seomjin River and streams flowing to the East Sea, Korea. Water temperatures were $17{\sim}23^{\circ}C$ during the spawning season, which ran from late September to early November in Seomjin River and early August to mid-October in streams flowing to the East Sea. The GSI and HSI variations of ayu population in Seomjin River increased earlier than in populations in streams flowing to the East Sea with similar variation in water temperature. Histological study of ovaries showed that the start of spawning of P. altivelis in Seomjin River was later than in streams flowing to the East Sea. Overall, fecundity increased with increase in SL and not by site specificity. The SL of P. altivelis increased as the river scale increased. Mean length of specimens from Seomjin River (river length: 223.86 km, river area: $4,911.89km^2$) was $194{\pm}15.3mm$, from Osip Stream (55.76 km, $393.78km^2$) $185{\pm}15.5mm$, from Yangyang Namdae Stream (54 km, $474.08km^2$) $142{\pm}11.8mm$, and from Joosoo Stream (21.1 km, $141.47km^2$) $136{\pm}16.7 mm$.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.1
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• pp.20-24
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• 2000

A 7-week growth trial was conducted to investigate the effects of yeasts (Kluyveromyces fragilis and Candida utilis) with or without cell wall chemical treatment (protoplasted) in formulated diets on growth and body composition of larval ayu (Plecoglossus altivelis). Three replicate groups of ap average weighing 100 mg were fed diets containing each level ($5{\%}$) of K. fragilis, protoplasted K. fragilis, C. utilis, protoplasted C. utilis or brewer's yeast as an additive. Survival rate of fish fed the diet containing protoplasted K. fragilis, C. utilis or protoplasted C. utilis was higher than that of fish tea the control diet (P<0.05). Body weight .gain of fish fed the diet containing protoplasted K. fragilis was higher than that of fish fed the control diet (P<0.05). Crude protein and ash contents of Ssh were not significantly affected by the different dietary yeasts (P>0.05), On the other hand, crude lipid content of fish fed the diet containing K. fragilis, protoplasted K. fragilis or brewer's yeast was higher than that of fish fed the control diet (P<0.05). Amino acids composition of fish was not significantly affected by the different dietary yeasts (P>0.05), except aspartic acid. The results suggest that protoplasted K. fragilis as an additive in micro-formulated diet can improve weight gain and body quality of larval ayu.

• Korean Journal of Ichthyology
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• v.20 no.3
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• pp.210-219
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• 2008

Monthly variation in species composition of upstream-migrating fish in the Cheonjeyeon Estuary was determined by analyzing fish data collected January~September 2004 and January~August 2007. Fish migrating from the sea to freshwater through the channels were collected by a rectangular net with a mesh size of 2 mm during the day and at night in the new moon. Of 14 species collected, ayu (Plecoglossus altivelis altivelis) and mullet (Mugil cephalus) predominated in abundance. Glass eels (Anguilla japonica) occurred mainly during the night from February to May. Other fishes collected included brackish-water gobiids (Gymnogobius urotaenia, Rhinogobius giurinus, Tridentiger obscurus, and Sicyopterus japonicus), freshwater fishes (Misgurnus anguillicaudatus and Rhynchocypris oxycephalus), and coastal marine fishes (Engraulis japonicus, Pempheris japonica, Plotosus lineatus, Takifugu niphobles, and Terapon jarbua). Ayu occurred during almost all sampling periods. They ranged principally from 55 to 100 mm total length (TL), with some fish larger than 100 mm TL collected after April. Mullet also occurred during almost all sampling periods. They ranged principally 25~58 mm TL, with some larger fish of 103~240 mm TL collected in February and April. That only a few freshwater and brackish-water fishes occurred in the study area is probably related to the freshwater systems having long been isolated from the continental systems and to the poorly developed estuaries in Jeju Island reflecting limited river discharge.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.09a
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• pp.437-438
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• 2005

• Proceedings of the Korea Water Resources Association Conference
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• 2005.09a
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• pp.439-440
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• 2005

• Proceedings of the Korea Water Resources Association Conference
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• 2005.09a
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• pp.420-421
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• 2005