• Korean Journal of Environment and Ecology
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• v.37 no.2
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• pp.151-162
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• 2023

This study investigated the characteristics of fish communities and inhabiting status of the endangered species, Rhodeus pseudosericeus, in the Geumdang Stream in Korea from March to October 2021. A total of 1,698 fish in 5 families and 25 species were collected from 7 survey stations during the survey period. The dominant species was Zacco platypus (relative abundance, 46.5%), and the subdominant species was Squalidus gracilis majimae (16.7%), followed by Rhynchocypris oxycephalus (12.0%), Z. koreanus (5.7%), Pungtungia herzi (3.2%), R. pseudosericeus (2.0%), R. notatus (1.9%), and Acheilognathus rhombeus (1.8%). Nine Korean endemic species (36.0%) were collected, including R. pseudosericeus, R. uyekii, Sarcocheilichthys variegatus wakiyae, Microphysogobio yaluensis, S. gracilis majimae, Z. koreanus, Cobitis nalbanti, Iksookimia koreensis, and Odontobutis interrupta. An exotic species, Micropterus salmoides, designated as an invasive alien species (IAS), was collected downstream. The investigation of the habitat patterns of the endangered species (class II), Rhodeus pseudosericeus, showed a habitat range of about 6 to 7 km in the middle of Geumdang Stream (RP-1 to RP-4), and this species inhabited the edge with water depths of 0.3 through 1.0 m with slow water flow and many aquatic plants. According to the community analysis results, the overall dominance and evenness indexes were low, while diversity and richness indexes were high, and the cluster structure was largely divided into upstream and middle-downstream areas. The river health (fish assessment index) evaluated using fish was assessed as good (3 stations), normal (3 stations), and bad (1 station), and water quality was evaluated as good both upstream and downstream. Compared to previous studies, the number of species was relatively similar, and among the species that appeared in the past, 13 species did not appear in this survey, while 6 species appeared for the first time in this survey. Disturbance factors included river construction, many weirs, and the appearance of the ecosystem-disturbing species, M. salmoides. Since Geumdang Strem has high conservation value because it is home to many species in the Acheilognathinae subfamily, including the endangered species R. pseudosericeus, continuous attention and systematic conservation measures are required.

• Korean Journal of Environmental Biology
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• v.41 no.3
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• pp.229-246
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• 2023

The bitterling (Cyprinidae, Acheilongnathinae) is a temperate freshwater fish with a unique spawning symbiosis with host mussels. Female bitterlings use their extended ovipositors to lay eggs on the gills of mussels through the mussel's exhalant siphon. In the present study, in April of 2020, we investigated spawning frequencies and patterns of three bitterling fish species in host mussel species in the Nakdong River basin (Hoecheon). During field surveys, a total of four bitterling and three mussel species were found. We observed bitterling's spawning eggs/larvae in the three mussel species: Anodonta arcaeformis(proportion spawned: 45.5%), Corbicula fluminea(12.1%), and Nodularia douglasiae (45.2%). The number of bitterlings' eggs/larvae per mussel ranged from 1 to 58. Using our developed genetic markers, we identified the eggs/larvae of each bitterling species in each mussel species (except for A. macropterus): A. arcaeformis (spawned by Acheilognathus yamatsutae), C. fluminea (A. yamatsutae and Tanakia latimarginata), and N. douglasiae (A. yamatsutae, Rhodeus uyekii, and T. latimarginata). Approximately 57.6% of N. douglasiae mussel individuals had eggs/larvae of more than one bitterling species, suggesting that interspecific competition for occupying spawning grounds is intense. This is the first report on bitterling's spawning events in the Asian clam C. fluminea from Korea; however, it should be ascertained whether bitterling's embryo undergoes successful development inside the small mussel and leaves as a free-swimming juvenile. In addition, the importance of its conservation as a new host mussel species for bitterling fishes needs to be studied further.

• Korean Journal of Ichthyology
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• v.36 no.3
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• pp.240-252
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• 2024

The distribution status of the nature monument species, Hemibarbus mylodon, was investigated from 2021 to 2024 in Geumgang River and Mujunamdae Stream (a tributary of the Geumgang River). In 2021 to 2023, five individuals from Gemgang River upstream were collected by Geumsan-gun, Chungchangnam-do. In 2021 to 2024, 1,592 induviduals juvenile from seven sites were collected by surveying 15 sites from Mujunamdae Stream. The main habitat of juvenile was about 0.3~1.5 meters water deep, 0.14~0.16 meters per second in the middle-upper stream of rock and sand bottom with slow rapids and pools. The age groups for H. mylodon estimated by the frequency distribution of total length in after spawning season (May) to October indicated the 10~65 mm is 0-year old, 75~90 mm is 1-year old group. In addition, over the 120 mm group is 2-years old, the 190~250 mm is more than 3-years old group. In 2024, we identified 35 spawning place from six sites were sites were collected by surveying 15 sites. Spawning place at the river bottom were top of the rapids, 30~60 cm (mean 48.2 cm) water deep, and the place was covered with stone and gravel, water velocity was 0.13~0.34 (mean 0.25 m/sec) meter per second. The spawning place size of the gravel piles was as follows: length 35~48 cm (mean 40.7 cm), width 25~37 cm (mean 34.5), and height 5~12 cm (mean 8.6 cm). Thus, H. mylodon reintroduced to Mujunamdae Stream has successfully settled down and increase in abundance within the natural habitat.