• Korean Journal of Ichthyology
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• v.31 no.2
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• pp.67-76
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• 2019

This study was conducted from 2017 to 2018 to determine habitat aspects of Acheilognathus signifier, an endangered species reintroduced (2010~2012) to Heukcheon Stream, a tributary of the Hangang River, Korea. A total of 329 individuals were collected in 2017 (two surveys) and 723 individuals were collected in 2018 (four surveys) at about 5 km habitat area, including the discharge station. A. signifier's habitat was about 0.4 to 1.2 meters deep in slow water flow upstream of the discharge area. It was a place with many boulders and cobbles. The spawning period was estimated from April to June in terms of spawning behavior and collected juvenile size. Sex ratio of females (438) and males (412) was 1 : 0.94. Estimated age of A. signifier based on their total length distribution during the spawning period (April) indicated that 1-, 2-, 3-year old groups and more than 4-year-old group were 32~43 mm, 50~61 mm, 62~75 mm, and 76~89 mm, respectively. Age-specific composition costs differed depending on the timing of the collection. They were relatively high in the order of first-year (juvenile)>third-year> and fourth-year or higher, showing a stable age structure. Thus, A. signifier reintroduced to Heukcheon Stream has successfully settled down and formed a stable population, showing a tendency to proliferate.

• Korean Journal of Ichthyology
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• v.33 no.3
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• pp.167-176
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• 2021

This study was carried out to clarify the egg, larvae and juveniles development of Abbottina springeri. For the experiments, the matured adults were collected at the Seowon-cheon, Dangjin-si, Chungcheongnam-do, in Korea. The amount of spawning of female A. springeri was about 1,225~2,100 (1,662±437, n=10). The fertilized eggs were circular in shape and 1.05~1.13 (1.08±0.02, n=30) mm in diameter. The hatching time was required 72 hours to 80 hours after fertilization under water temperature of 22℃. The newly hatched larvae were 2.10~2.23 (2.16±0.04, n=10) mm in total length and had egg yolk in the abdomen but the mouth was not opened. At 5 days after hatching, the preflexion larvae were 3.19~3.30 (3.24±0.03, n=10) mm in total length and the most of yolk-sac was absorbed. At the 15 days after hatching, the flexion larvae were 4.97~5.30 (5.13±0.12, n=10) mm in total length and the tip of the caudal fin was began to bend upward. At the 25 days after hatching, the postflexion larvae were 8.97~9.60 (9.44±0.16, n=10) mm in total length and the tip of the caudal fin was bent at 45°. At the 35 days after hatching, the juvenile were 12.0~13.5 (12.7±0.53, n=10) mm in total length and all fin-rays (iii7 dorsal fin, iii6 anal fin, i7 ventral fins) were reached a constant number of each part.

• Korean Journal of Ichthyology
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• v.33 no.4
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• pp.297-303
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• 2021

In this study, nine major sites of Yulcheon stream, a principal tributary of the Seomjingang River, were surveyed from April 2020 to October 2020, and their fish fauna and community structure were analyzed. A total of five families and 19 species of fish were identified. Among the 19 species, seven species were found to be endemic to Korea: Rhodeus uyekii, Squalidus gracilis majimae, Microphysogobio yaluensis, Odontobutis interrupta, Cobitis tetralineata, Zacco koreanus, and Squalidus chankaensis tsuchigae. Among five families, the family Cyprinidae had the largest number of species (15), whereas the rest of the four families: Gobiidae, Odontobutidae, Cobitidae, and Osphronemidae, had one species each. The two dominant species in the family Cyprinidae were identified as Z. platypus and Z. temminckii. The community index of nine major sites of Yulcheon stream was 0.499 dominance, 2.279 diversity, 0.774 evenness, and 2.594 species richness. The number 3 site had 14 species, the largest number of species among all sites, and the dominance rate (0.480) was low, whereas diversity (2.173), and species richness (2.701) were the highest. As a result of cluster analysis, clusters matched according to the structure of the river types, but St. 9, which confirmed a relatively small number of populations, showed a structure similar to that of the upstream section. In the case of St. 5, a separate cluster was formed by a large number of species and populations.

• Korean Journal of Ichthyology
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• v.33 no.2
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• pp.57-63
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• 2021

This study was carried out to clarify the egg, larvae and juveniles development of Carassius cuvieri in Nakdong River, Gyeongbuk. The amount of spawning of female C. cuvieri was about 30,400~44,900 (average 37,650±7,250). The egg shape was circular and the size was 1.24~1.37 mm (average 1.31±0.04 mm, n=30). At 100 hours after fertilization, more than of the total embryos were hatched. The newly hatched larvae had an 4.69~5.65 mm in total length (average 5.15±0.31 mm, n=10) and had egg yolk in the abdomen. At 3 days after hatching, the preflexion larvae absorbed all egg yolk was 6.27~6.70 mm in total length (average 6.59±0.08 mm, n=10). On the 10 days after hatching, the postflexion larvae were 8.71~8.92 mm in total length (average 8.81±0.07 mm, n=10), and the tip of the caudal fin was bent at 45°. On the 42 days after hatching, the total length of 15.1~16.8 mm (average 15.8±0.57 mm, n=10) was transferred to juvenile as the number of fins was (iii17 dorsal fins, iii4 anal fins) reached a constant number of each part.

• Korean Journal of Ichthyology
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• v.33 no.1
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• pp.8-14
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• 2021

Spawning behavior of the endangered Korean fish, Microphysogobio koreensis, was investigated in the Seomjingang (river), Imsil-gun, South Korea, during the spawning season, April to May 2012. The mating system of M. koreensis, a broadcast spawner, was a primitive spawning mode, and involved one male and one female, unlike group spawning fishes. Spawning behavior of M. koreensis in the wild were observed in eight patterns as resting, male chase, body beating, parallel swim, female withdrawal, male competition, spawning and not guard while spawning behavior in the glass tank were verified in six patterns as resting, male chase, body beating, parallel swim, spawning and not guard. In particular, a behavioral attempt of the pre-spawning stage showed more frequently in the wild than in the glass tank. We assume that difference of spawning behavior might be implication on behavioral restrictions in small and narrow indoor glass tank.

• Korean Journal of Ichthyology
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• v.34 no.1
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• pp.34-43
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• 2022

A distribution survey was conducted from March to August 2021 to evaluate the distribution status, habitat characteristics, and threat of extinction of the Korean cold-water fish Ladislabia taczanowskii Dybowski (Cypriniformes, Cyprinidae). Historical distribution reports were divided into 1997~2005, 2006~2012, 2013~2019, and distribution surveyed 169 sampling sites, and 1,040 individuals were collected from 72 sites. Areas where the habitat was confirmed were Namhan River (27 stations), Han River (17 stations), Bukhan River (16 stations), Samcheok Osipcheon (4 stations), Yeongokcheon (3 stations), Gangneung Namdaecheon (2 stations), Jeoncheon (1 station), Chucheon (2 stations). The main habitat of L. taczanowskii was upstream of the river with a high altitude of more than 300 m, 2~30 m water flow width, 0.3~1.5 m water depth, and high ratio (50~90%) boulder bottoms. The main reasons for the decline in population size were assumed as river works, construction of reservoirs and bridges, discharge of contaminated water into the river, the inflow of summer vacationers, and weir. Compared to our results there exists evidence that states a 36.1% reduction in occupancy within 10 years, in a small appearance range (7,820 km²) and occupancy area (288 km²), number of disconnected locations (19 locations), and a decline in habitat quality. Therefore, L. taczanowskii is now considered as Vulnerable (VU) based on the results (VU A2ac, Near meets B1b (i, ii, iii)+B2b (i, ii, iii)) of IUCN Red List categories and criteria. Lastly, the conservation plan of Ladislabia taczanowskii was discussed.

• Korean Journal of Ichthyology
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• v.35 no.3
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• pp.160-170
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• 2023

Life history of the endangered endemic species, Rhynchocypris semotilus, was investigated to obtain baseline data for its ecological characteristics in Songhyeoncheon, Hyeonnae-myeon, Goseong-gun, Gangwon-do, Korea from April to October, 2022. A total of 10 families and 18 species of fishes were collected from 4 survey stations, and R. semotilus was a subdominant species in the survey period (seven times). The main habitat of R. semotilus was the middle-upper stream of rock and boulder bottoms with aquatic plants and slow rapids and pools. The age groups for R. semotilus estimated by the frequency distribution of total length in spawning season (May) indicated the 4~12 mm is 0-year old, 32~49 mm is 1-year old, the 50~65 mm group is 2-years old, the 66~91 mm is 3-years old, and the 92~116 mm is more than 4-years old, and showed rapid growth from May to September. Total length range of female and male were the relatively similar, and sex ratio (♂/♀) was 0.78. The spawning period is from May to July (water temperature is 17 to 21℃), and gonad was developed more than three years old (more than TL 66 mm). In May, the gonadosomatic index (GSI) was 10.6±2.99% for females and 8.2±2.34% for males, fecundity was 6,830±1,943, and mature eggs size was 1.34±0.16 mm. Finally, life history characteristics of R. semotilus was discussed between the genus Rhynchocypris and Phoxinus species.

• Korean Journal of Ichthyology
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• v.36 no.1
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• pp.68-76
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• 2024

To reveal the feeding ecology of Rhynchocypris semotilus, the survey was conducted in Songhyeoncheon, Songhyeon-ri, Hyeonnae-myeon, Goseong-gun, Gangwon-do in April 2022. As a result of analyzing the contents of the stomach using the index of relative importance (IRI), the important prey organisms were mainly Trichoptera (46.6%), Ephemeroptera (27.6%), Diptera (12.6%), Odonata (9.7%), Plecoptera (2.8%), Coleoptera (0.6%), and Hemiptera (0.1%) of Class Insecta, Phylum Arthropoda in that order. As a result of analyzing the trend by calculating the index of relative importance (IRI) for each age, it was found that those born in the same year mainly feed on relatively small Ephemeroptera and Diptera, but the proportion of these gradually decreases as they grow. And the proportion of relatively large Trichoptera and Odonata gradually increased, turning them into the most important food source for those over 3 years old. Additionally, prey size was the smallest at 2.8±2.5 (0.6 to 9.0) mm for individuals born in the same year, but gradually increased to 5.1±6.1 (1.1 to 17.0) mm for individuals born more than 3 years. As a result of examining prey selectivity, Plecoptera (+0.78), Trichoptera (+0.66), (+0.66), Coleoptera (+0.66), and Hemiptera (+0.03) showed positive selectivity, while Amphipoda (-1.00), Ephemeroptera (-0.24), Odonata (-0.13) and Diptera (-0.05) showed negative selectivity.

• Korean Journal of Ecology and Environment
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• v.57 no.3
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• pp.148-161
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• 2024

This study conducted morphological and molecular phylogenetic analyses on three presumed natural interspecific hybrids of the genus Sarcocheilichthys, collected from the main stream of the Seomjin River and its tributary, Dongbokcheon Stream, as well as their parent species, S. nigripinnis morii and S. variegatus wakiyae, to identify whether they are natural hybrids and to determine their maternal and paternal species. The results of the molecular phylogenetic analysis clearly demonstrated that the three presumed natural hybrids are indeed natural hybrids of S. nigripinnis morii and S. variegatus wakiyae, with S. nigripinnis morii identified as the maternal species and S. variegatus wakiyae as the paternal species. The three natural hybrids exhibited intermediate or unique morphological traits that were not biased towards either parent species, and distinct morphological characteristics were observed in the dorsal fin and caudal fin. In the water bodies where the natural hybrids were collected, a variety of Acheilognathinae species and spawning hosts coexisted alongside the parent species S. nigripinnis morii and S. variegatus wakiyae. It is presumed that the overlapping spawning periods and locations of S. nigripinnis morii and S. variegatus wakiyae promoted the occurrence of hybrids. The unidirectional occurrence of natural interspecific hybridization is attributed to interspecific competition and population imbalance, and the sneaker behavior of S. variegatus wakiyae males was proposed as an important mechanism.

• Korean Journal of Ecology and Environment
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• v.57 no.3
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• pp.134-147
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• 2024

Present study investigated fish community at 12 sites within Yudeungcheon Stream in October 2018 and May 2019 to understand the inhabit status of the endangered species Pseudopungtungia nigra. We collected 39 species and 2,554 individuals of fish, and the Fish Assessment Index (FAI) was evaluated as "Good (B)" with an average score of 66.8. Among collected fishes, 15 endemic and 2 invasive species, Micropterus salmoides and Lepomis macrochirus were identified. In the distribution survey of P. nigra, it appeared in a range of approximately 12 km from Maebawiyuwonji Park (St. 5) to Budnaedari Bridge (St. 10). Based on population collected in May, the age of P. nigra (female) were divided into three groups by the length-frequency distribution method: 1 year old (60~76 mm), 2 years old (82~99 mm), and more than 3 years old (100~117 mm). Total length of the minimum maturity individual was 60 mm, and was a 1 year old. The estimated average population size using the Jolly-Seber method was 5,804 individuals in the Suryeongyo Bridge. Our study provides fundamental information about the fish community and River health assessment in Yudeungcheon Stream. Furthermore, we are expected to provide ecological information of the P. nigra, consequently helping to establish conservation and restoration plans for endangered species.