• Korean Journal of Ichthyology
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• v.5 no.2
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• pp.226-234
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• 1993

Cobitis sinensis-longicorpus complex considered as hybrid origin between C. sinensis and C. longicorpus coccurred ommonly in the upper streams of the Nakdong River, Korea. Histological examinations of their gonad were accompanied with 272 individuals of C. sinensis-longicorpus complex collected. Most of fishes collected were females, however, only 6 individuals were found males. The ovarian tissues of females are completely fertile undergoing normal oogenensis. In the male gonads, testicular lobule structure with abnormal vacuolar tissues were observed. Spermatogonia and spermatocytes were also observed of their testis however spermatids or sperms were not shown in their developmental stages. From these facts, we infer that female population of C. sinensis-longicorpus complex may be unique reproductive hierarchy accomplishing their reproduction with participation of males of their closely related bisexual species.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.3
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• pp.456-463
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• 2020

The diet of the walleye pollock Gadus chalcogrammus, was studied by examining the stomach contents of 864 individuals. Using gill nets, samples were collected monthly from January to December 2017 in Jugwang, Sokcho, Yangyang, Uljin, Ganggu, and Gampo, Korea. The specimens ranged in total length (TL) from 16.6 to 75.2 cm. G. chalcogrammus fed mainly on Euphausia pacifica (Euphausiacea) and less on Cephalopoda, Pisces, Mysidacea, and Macrura. The results indicated that G. chalcogrammus is a specialist feeder, feeding mainly Euphausiacea. With growth, however, its diet shifted from Euphausiacea to Cephalopoda, Macrura and Pisces. Smaller individuals (<40.0 cm TL) consumed mainly Euphausiacea. The proportion of Euphausiacea decreased with increasing body size, whereas the consumption of Cephalopoda and Macrura increased gradually.

• Korean Journal of Ichthyology
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• v.22 no.4
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• pp.225-229
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• 2010

A intergeneric hybrid between Rhodeus uyekii and Acheilognathus signifer was collected in the Jojongcheon Bukhan River. The hybrid showed intermediate characteristics of two parental types in some key characters, such as color pattern of body, pigmentation of dorsal, anal, and caudal fins, and body spot and stripe. In addition, the hybrid had a fairly large number of lateral line scales, while it lacked a barbel, which is known as a key intergeneric character. The probable occurrence of a natural hybrid is supported by a viable $F_1$ hybrid produced with the parental species.

• Korean Journal of Ichthyology
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• v.12 no.1
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• pp.25-32
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• 2000

The structure of skin was studied in Iksookimia longicorpus based on the micro-anatomical investigation of skin fragments taken from four regions. The epidermis was distinguished by two types of skin glands, a small mucous cell and a large club cell. The mucous cell was acid sulfomucins (some sialomueins) but the club cell did not give any histochemical tests for mucosubstances. The presence of a well defined lymphatic system with small lymphocytes was established in the stratum germinativum layer of the epidermis. A large number of blood capillaries run very close to each other just below the basement membrane, and a definite area giving AB and PAS positive was present between the basement membrane and scale.

• Korean Journal of Ichthyology
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• v.20 no.3
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• pp.233-235
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• 2008

A 123.2 mm TL female of Iksookimia longicorpa with a laminar circularis at the base of its pectoral fin was collected in the Hoeya River, Korea, on May 5, 2008. The specimen had full-grown ovaries like those of normal females. Its pectoral fins were larger than those of normal females, but was smaller than those of males. The laminar circularis of the pectoral fin base was more similar to normal males in its shape but was less developed. The ovaries in the individual had about 3,148 mature eggs, with egg sizes approximately $1.26{\pm}0.11mm$.

• Korean Journal of Ichthyology
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• v.24 no.1
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• pp.56-61
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• 2012

The distribution status and population size of the endangered species, $Cobitis$ $choii$, were investigated in the Guem River, Korea. From 1984~2004, this species occurred at 20 survey stations; however, their numbers have but rapidly decreased in recent years (2006~2011), during which time they were only observed at six stations. The area of their habitat is narrow and occurs in primarily downstream, sandy zones. Using the mark-recapture method, populations were estimated at 9,106 and 34,717 individuals for the main habitats of Baekgok and Ji Stream, respectively.

• Korean Journal of Ichthyology
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• v.10 no.2
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• pp.250-259
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• 1998

This study was carried out to reveal the taxonomic status of the two mullets, Chelon affinis and Chelon haematocheilus from Korea by comparison of their morphological characteristics. Chelan affinis, occurred in the southern coastal area, is a distinct species characterized by having a keel on the middorsal line in front of the spinous dorsal fin. However, Chelon haematocheilus, found in the all coastal areas of Korea excluding Cheju island is easily distinguished from the former in having the deep flat head. By comparison of five groups of Chelan haematocheilus, Kunsan group is slightly differed from others in the height of anal fin and caudal peduncle length. Although Chelon affinis is similar with Chelan haematocheilus in the view of meristic characters, they are distinguished from each other in the number of pyloric caeca and lateral line scales.

• Animal Systematics, Evolution and Diversity
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• v.6 no.1
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• pp.1-16
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• 1990

The skull and superficial cephalis muscles of Coreoleuciscus splendidus Mori was investigated comparatively with other some fishes of the family Cyprinidae to study on the systematic position of this species. Coreoleuciscs splendidus was unique in the morphology of sphenotic process and the urohyal and this species differ from the true bottom dwellers of the subfamily Gobioninae in the strucutre of cephalic lateral-line canals, the relation of parasphenoids with pterotic and prootic, the morphology of urohyal , basihyal , hypobranchial, and , particulary, the configuration of adductor manibulae complex. With reference to the information so far obtained , the taxonomic position of the present species was discussed in the Cyprinidae.

• Korean Journal of Ichthyology
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• v.25 no.2
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• pp.74-81
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• 2013

Factors influencing spawning or respawning conditions of the bitterling, Acheilognathus signifer were investigated in the aquariums. Inducing the female spawning was more sensitive to the mussel than the male. The ovipositor of the female was periodically elongated and reduced from 4 to 6 days with the presence of mussel. During of the elongated state of the ovipositor was 1 to 2 days. As the result of natural spawning in the aquariums, it takes 1 to 3 days (mean 1.6) to spawn. The most important factor to respawn spawned females again was the mussel. It takes 11 to 53 days (mean 29.5) from extraction to reextraction of females which have elongated ovipositor. The egg numbers of reextraction were 2 to 41 (mean 19). This experiments showed the tendency the more standard length of females grows, the more the number of extracted eggs increases.

• Korean Journal of Ichthyology
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• v.21 no.1
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• pp.55-60
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• 2009

Korean bitterling Acanthorhodeus gracilis Regan, 1908 is very similar to Acheilognathus chankaensis (Dybowski, 1872) having 12~14 dorsal fin rays, 10~11 anal fin rays and 35~36 lateral line scales. By analyzing these specimens and original descriptions, diagnostic characteristics of the genus Acanthorhodeus were included in the genus Acheilognathus and Acanthorhodeus gracilis was defined as a junior synonym of Acheilognathus chankaensis. The provisional keys are provided for identifying the nine species of Acheilognathus from Korea.