• Korean Journal of Ichthyology
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• v.28 no.2
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• pp.72-78
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• 2016

The age and spawning characteristics of Iksookimia pacifica were investigated in this study to provide baseline data for its ecological characteristics in the Bukcheon (stream), Goseong-gun, Gangwon-do, Korea from January to December, 2013. Age groups of I. pacifica (female) estimated by the frequency distribution of total length in the spawning season indicated that the 30~49 mm group is 1 year old, the 50~74 mm group is 2 years old, the 75~99 mm group is 3 years old, the 100~124 mm group is 4 years old, and the 130~160 mm group is $5{\leq}$years old. The sex ratio (♂/♀) was 0.63, and females were 30~60 mm larger than males. The lamina circularis at the base of pectoral fins in males as a secondary sexual character was created at the 13th month after hatching. The spawning season according to the gonadosomatic index (GSI) was July to August (main spawning season in July) with water temperatures of $20{\sim}25^{\circ}C$. The average number of eggs was $2,503{\pm}1,337$ with a diameter of $1.11{\pm}0.04mm$ in mature eggs.

• Korean Journal of Ichthyology
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• v.31 no.1
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• pp.16-22
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• 2019

Investigations on the study of the distribution aspects and extinction threat evaluation of the Korean endemic species, Iksookimia pacifica were done from 2017 to 2018 in Korea. During the study period, the samples of I. pacifica were collected in 17 streams, 46 sites (from Baebongcheon Stream of Goseong-gun to Gunsuncheon Stream of Gangneung-si) among the noted 33 streams and 104 sampling sites investigated. The population size of I. pacifica was relatively large in streams such as Bukcheon, Baebongcheon, Hwasangcheon, Cheonjincheon, Ohhocheon Stream etc., but the population size was small in streams such as Sacheoncheon, Namcheon, Gangneung Namdaecheon Stream etc. The main habitat of I. pacifica was the downstream pool of clean water with slow velocity and sand bottoms, and their sensibility was estimated to be due to river work and water pollution. Comparing the previous records of the appearance of I. pacifica, they were first seen in Sampocheon Stream, but they did not appear in Jusucheon, Jeoncheon, Samcheok Osipcheon Stream. Given this evidence as noted for the 19.5% reduction in occupancy within 3 generations, in small appearance range ($1,343km^2$) and small occupancy area ($184km^2$), the number of locations were many (18) and the population was relatively large within the range of habitat. Therefore, I. pacifica is now considered a Near Threatened (NT) based on the IUCN Red List categories and criteria.

• Korean Journal of Ichthyology
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• v.27 no.4
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• pp.275-283
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• 2015

Habitat characteristics and feeding ecology of Iksookimia pacifica were investigated in this study to provide baseline data for its ecological characteristics in Bukcheon (stream), Goseong-gun, Gangwon-do, Korea. The main inhabit of I. pacifica was found to be sand bottoms of Bb or Bc river type with slow water flow. Based on studies of their habitat preferences according to age, their preference for sand bed was the same. However, their preference for depth and velocity was different. When their age was increased, their depth preference was also increased ($24.9{\pm}17.61cm$ for 0+ year, $69.6{\pm}30.32cm$ for 1+ year, $82.4{\pm}33.30cm$ for 2+ years, and $90.0{\pm}31.55cm$ for $3+{\leq}$ years). The water velocity was found to be 3.8 ~ 4.0 cm/sec for ages between 0+ and 1+ and 6.0 ~ 7.3 cm/sec for ages between 2+ and $3+{\leq}$. They were active on sand from March to November. They would hibernate in sand during the winter season. During the day from 12 pm to 24 am, they were highly active with high food consumption. Their main food sources analyzed with index of relative importance (IRI) include Chironomidae (76.7%), Simuliidae (10.3%), Rotatoria (7.3%), and Arcellidae (2.2%). Their juveniles (total length 20~40 mm) would feed on small-sized preys such as Rotatoria, Copepoda, and Arcellidae. Older I. pacifica would feed on big-sized preys such as Chironomidae and Simuliidae.

• Korean Journal of Ichthyology
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• v.21 no.sup1
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• pp.7-28
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• 2009

The family Cobitidae of Korea was reviewed as 16 species in 5 genera with the key to species for the identification by the external features. The three genera of Iksookimia, Koreocobitis, and Kichulchoia erected from the genus Cobitis were reclassified based on the presence or absence of Gambetta’s zones on the body sides, their body pigmentation, the shape of lamina circularis in males, the number of unbranched anal fin rays, and some molecular phylogenetic data. By the results of these reexamination, the generic names of the three species were changed as Cobitis choii, Iksookimia pacifica, and Kichulchoia mutifasciata. It was remarked biogeographically that most species of genera Cobitis, Iksookimia, Koreocobitis, and Kichulchoia show the disjunct distributions with bottom-dwelling preferences as endemic to Korean peninsular. Three species of Cobitis choii, Kichulchoia brevifasciata, and Koreocobitis naktongensis are considered to be critically endangered according to the severe habitat destruction and the alteration of river topography.

• Korean Journal of Environment and Ecology
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• v.31 no.5
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• pp.461-471
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• 2017

Population genetic studies of 10 groups of Iksookimia pacifica were conducted to investigate the genetic diversity and population genetic structure across its known range in South Korea. Population DNA sequences of one mitochondrial gene (mtCOI) and three nuclear genes (IRBP, EGR2B, RAG1) were examined in samples collected from ten streams that flow into the East Sea. Both mitochondrial and nuclear sequences exhibited significant differentiation among populations except a few cases. The Bayesian analysis of the multi-locus genotypes inferred from the DNA sequences of nuclear genes clustered the individual fish largely into two geographical groups: a northern group (from Baebong stream to Cheonjin stream) and a southern group (Yangyangnamdae stream to Gangneungnamdae stream). Given that the streams flowing into the East Sea are geographically isolated water systems, such separation of genotypes can be interpreted by the geographical separation of common ancestors into north and south that had colonized South Korea. Since the initial geographical separation of the ancestral population by north and south, the ancestral groups seem to have experienced further differentiation into the current genetic clusters through the physical isolation of streams by the East Sea in each region. It is notable that many individuals in the Jasan stream formed a genetic cluster with those of Yangyangnamdae and Gangneungnamdae streams which are distant from each other. In addition, mitochondrial gene showed low genetic differentiation between some neighboring populations and very low level of genetic diversity in several populations. The present population genetic study will provide valuable information for the conservation and management of the Korean endemic fish species, I. paicifica.

• Korean Journal of Ecology and Environment
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• v.46 no.2
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• pp.192-204
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• 2013

Fish community structure and inhabit status of endangered fish species were investigated during April to November 2011 in Baebong Stream, Gangwon do, Korea. The number of fish species inhabiting the upper section (Stations 1~3, 5) was 14 and the stream bottoms were mostly composed of cobbles and boulders (Aa-type). Meanwhile, the number of fish species inhabiting the lower section (Stations 4, 6, 7) was 26 and the stream bottoms were mostly composed of pebbles, cobles and sand (Bb-type). A total of 26 species belonging to ten families were found in the stream during the survey period. The dominant and subdominant species were Rhynchocypris steindachneri (31.1%) and Squalidus multimaculatus (13.3%), respectively, and others such as Pungitius kaibarae (11.0%), Zacco koreanus (7.8%), Misgurnus anguillicaudatus (7.0%), Iksookimia pacifica (5.5%) and Z. platypus (5.3%) were followed in the order. Four species of Squalidus multimaculatus, Z. koreanus, I. pacifica and Liobagrus andersoni were endemic to Korea. And, Lethenteron japonica, L. reissneri, Pungitius sinensis and Cottus hangiongensis were endangered fish species in this stream. Oncorhynchus keta, L. japonica and Tribolodon hakonensis were anadromous species, and Plecoglossus altivelis was an amphidromous species. The similarity index based on species composition and abundance clearly divided the fish community structure of the Baebong Stream into two sections fragmented by a weir installed into the stream. It is necessary to install a fish ways on the weirs for a fish migration and movements.

• Korean Journal of Environment and Ecology
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• v.29 no.5
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• pp.718-728
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• 2015

The fish community and inhabiting status of introduced fish were surveyed at nine stations of Gangeungnamdae stream from September 2013 to May 2014. A total of 36 species of fourteen families were collected from the survey stations and among them, Pungitius sinensis was identified as endangered species. There were nine Korean endemic species (25%) including Coreoleuciscus splendidus. Dominant species were Rhynchocypris steindachneri (St. 1), Zacco koreanus (St. 2, 4, 5, 6), Ladislabia taczanowskii (St. 3)), Zacco platypus (St. 7, 8) and Tribolodon hakonensis (St. 9). Of the 11 introduced species fishes in Gangeungnamdae stream, L. taczanowskii, Pungtungia herzi, Coreoleuciscus splendidus, Squalidus gracilis majimae, Pseudogobio esocinus, Rhynchocypris kumgangensis, Z. platypus, Z. koreanus, Koreocobitis rotundicaudata, Liobagrus andersoni and Coreoperca herzi were released from Han river water zone in Korean. Rapidly expanded population and distribution of introduces fishes were Z. platypus, Z. koreanus, P. herzi and S. gracilis majimae, but L. taczanowskii, C. splendidus, R. kumgangensis were not rapidly expanded population. Settlement but very small population fishes were C. herzi and L. andersoni. When reduced 3% fishes of relative abundance with previous data (1973), R. steindachneri, Orthrias toni, Iksookimia pacifica, Plecoglossus altivelis, P. sinensis and Gymnogobius urotaenia, and R. steindachneri was most reduced from 56.1% to 12.9%.

• Korean Journal of Ecology and Environment
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• v.54 no.2
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• pp.130-141
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• 2021

By reviewing previous literature, we analyzed the food sources of 20 out of 29 endangered fish species from freshwater ecosystems in South Korea. A total of 19 studies reported that food sources of 20 endangered fish species included 20 phyla, 31 classes, 58 orders, 116 families, and 154 genera. Arthropod, insecta, diptera, and chironomidae were the most fed animal food sources according to different resolution of taxa index on phylum, class, order and family. Similarity, bacillariophyta, bacillariophyceae, naviculales, and cymbellaceae were the most fed abundant plant sources. A larger number of fish species were reliant on animal food sources than plant food sources. 18 of the endangered fish preyed on arthropods, whereas only 6 species consumed bacillariophyta. To characterize the feeding groups of the 20 fish species, a hierarchical clustering analysis and non-metric multidimensional scaling analysis were conducted. The fish species were divided into two groups: 1) insectivores and 2) planktivores. A network analysis, which associated the link between endangered fishes and food sources, also revealed the same two groups. The highest hub score of food sources was for macroinvertebrates, including diptera (0.47), ephemeroptera (0.42), and trichoptera (0.38), based on the network analysis. Niche breadth was used to calculate the diversity of the food sources. Phoxinus phoxinus (0.57) showed thehighest food source diversity among the fish species, whereas Iksookimia pacifica (0.01) showed the lowest. This study will be utilized for the conservation and restoration of the endangered fish species.