• Journal of Ecology and Environment
• /
• v.44 no.1
• /
• pp.54-61
• /
• 2020

Background: Most fish undergo prey switch from juvenile to adult. It is thought that slightly different feeding habits occur among adult fishes due to growth, spawning, habitat change, and so on. Therefore, the diet of the John Dory Zeus faber (≥ 24 cm TL) was studied in the coastal waters of Korea by analysis of stomach contents, with comparison by season and size class of diet composition and prey diversity. Monthly samples were taken from February 2017 to January 2018. Results: The results showed that the John Dory was a piscivorous predator, and pisces had occupied 82.3% of IRI%. Trichiurus lepturus and Trachurus japonicus were important preys in all size classes and seasons. Diet composition differed among the size classes and seasons (Chi-square test, P < 0.05). As body size of Z. faber increased, the occurrence of benthic fish (Glyptocephalus stelleri) tended to increase. The seasonal prey composition also changed depending on the abundant species of each season. Conclusions: Z. faber is a piscivorous predator. The consumption habits of Z. faber appear to different results by their size and seasons. This study suggests that Z. faber could be considered an opportunistic predator.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.42 no.4
• /
• pp.240-258
• /
• 2006

The potential of ecosystem-based fisheries management is recently recognized to be very important to improve the sustainability of fisheries resources. Under the depressed condition of many fisheries resources, this recognition has been expanded and more effort has been taken to improve this approach. Taking ecosystem concept includes the use of other tools of management in addition to fisheries regulation, such as stock and productivity enhancement, provision of physical structure, or marine protected areas. In the ecosystem-based fisheries management approach, it would require to holistically consider ecological interactions of target species with predators, competitors, and prey species, the effects of climate on fisheries ecology, the complex interactions between fishes and their habitat, and the effects of fishing on fish stocks and their ecosystem. Fisheries management based upon the understanding of these factors can prevent significant and potentially irreversible changes in marine ecosystems caused by fishing. A useful approach for analyzing tropho-dynamic interactions and mass-balance in marine ecosystems is introduced to demonstrate the complexity and usefulness of the ecosystem approach, which was applied to a small ecosystem in Korea. Korea should seriously consider to take the ecosystem-based approach to fisheries management, since most major fish stocks are currently depleted due to many reasons such as overfishing, land reclamation and coastal pollution.

• Journal of Korean Society on Water Environment
• /
• v.31 no.1
• /
• pp.1-11
• /
• 2015

In this study, the attraction efficiency of the by-pass fishway installed at Dalseong Weir in Nakdong River was assessed according to operation of the attraction waterway by using River2D which is a two-dimensional physical habitat simulation model. The model was calibrated and validated through the measured water elevation. The attraction efficiency of the fishway was evaluated at the low flow condition because the target fish, Zacco platypus (Z. platypus), have moved frequently up and downstream at the spawning season from April to June. From simulation results, it can be deduced that the attraction efficiency at situation of open attraction waterway is superior to that of close attraction waterway. Also it is shown that velocity field at inner region of the fishway is suitable for migration of the fish.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.49 no.1
• /
• pp.1-17
• /
• 2013

The investigation for species composition and catch in the Korean deep-water of the East Sea (also known as Sea of Japan) was carried out with trammel nets of 7 mesh sizes (6.1~24.2cm) offshore Donghae (2006) and Yangyang (2007) of Korea. The catches were 1,268kg and composed of 37 species between 200m and 1,200m in depth. The principal species caught were Taknka's snailfish, salmon snailfish, red snow crab, hunchback sculpin, snow crab, spinyhead sculpin, Tanaka's eelpout, Alaska cod and so on. Those were target fish for commercial value except salmon snailfish. The mesh sizes for the largest catch were 10.6cm and 15.2cm in the fishing ground of Donghae and Yangyang, respectively. The habitat of snow crab was shallower than that of red snow crab in both areas. Trammel net enabled to investigate fish in deep-water with small fishing vessel and rather cheap expenses in contrast to bottom trawl that required too much of it. With increasing inner mesh size of trammel net the mean size of some principal species such as Taknka's snailfish, spinyhead sculpin, hunchback sculpin, Pacific cod, snow crab, red snow crab and hybrid between snow crab and red snow crab tended to be large in certain range of mesh size.

• Journal of Aquaculture
• /
• v.22 no.1
• /
• pp.83-91
• /
• 2009

The Korean doty barbel Hemibarbus mylodon (Cypriniformes; Cyprinidae) is a critically endangered freshwater fish species mainly because of its natural habitat degradation. Three full-length complementary DNA (cDNA) clones representing different muscle actin isoforms were isolated and characterized. The three muscle actin isoforms were 1,294-1,601 bp long with the identical open reading frames of 1,134 bp with the deduced amino acid residues of 377. They showed 83.9-87.2% identities in the coding nucleotide level and 96.8-98.1% identities in the amino acid level. Phylogenetic analysis with the coding nucleotide sequences revealed that three muscle actin isoforms of H. mylodon formed strongly supported monophyletic groups with one of cypriniform skeletal $\alpha$-actin (acta1), cypriniform aortic $\alpha$-actins (acta2), and uncharacterized Danio rerio muscle actin isoform/Salmo trutta slow muscle actin (a novel muscle actin type). Our phylogenetic tree further suggested that cypriniform acta2 only showed the orthologous relationship to tetrapod acta2. Other multiple actin isoforms from diverse teleostean taxa were however clustered to no tetrapod orthologs, i.e., acta1, cardiac $\alpha$-actins (aetc1), acta2, and enteric $\gamma$-actin (actg2). This result strongly suggested that teleostean muscle actins have experienced different and complicated evolutionary history in comparison to mammalian counterparts.

• The Korean Journal of Malacology
• /
• v.25 no.3
• /
• pp.231-236
• /
• 2009

This study describes biological environmental characteristics in natural habitats of Haliotis diversicolor in the coastal area of Sungsanpo located in the eastern coast of Jeju-do, Korea. The field survey was monthly conducted from May 2006 to February 2007. H. diversicolor, sea urchin, turban shell and marine algae were collected by two divers using SCUBA. The species composition of demersal fishes were seasonally investigated by fish traps in 2007. During the study period, more than 67% of H. diversicolor and sea urchin were found in the depth shallower than 5 m, and more than 64% of turban shell were found in the depth deeper than 3 m. The dominant algal species in May were generally Undaria pinnatifida, Ecklonia cava, Sargassum. spp. and coralline algae. Most of demersal fishes collected by the fish traps were wrasses which have been reported as a major predator of young abalone.

• Korean Journal of Environmental Biology
• /
• v.38 no.1
• /
• pp.30-39
• /
• 2020

The changes in fish stock and biomass before and after fishway renovation located in a Korean estuary were studied and fluctuations in the economic value of the fish resources were estimated. The target fishway located in the east coast area in Korea was renovated in 2014 from the small fish ladder to the ice-harbor fishway. Monitoring was continued for five consecutive years after the renovation(2015 to 2019). Since the renovation of the fish passage, the economic values increased with increases in the fishery resources, except for in 2016 when the drought impact was severe. The yearly average incremental increase in the five years after the renovation was about 227%. The increase in economic value is believed to be due to the increased population of migratory fish as a result of habitat expansion. The exponential rise model showed an increase in economic value with increasing fishery resources (R²=0.896). The model coefficient contributing to economic analysis was 0.582 and the maximum economic value after the renovation was estimated at about 30.4 million. The economic value would be a useful index for quantitative comparison in terms of ecosystem services before and after renovation.

• Ecology and Resilient Infrastructure
• /
• v.2 no.1
• /
• pp.22-32
• /
• 2015

This study investigated the difference in fish community structures in a main channel and an isolated former channel, considering the environmental factors in the Mangyeong River, Korea. Principal component analysis (PCA) with environmental factors showed that former channels were composed of a fine substrate covered by in-stream vegetation, whereas the main channel was covered by a wide range of substrates with a higher dissolved oxygen and conductivity. The result of the hierarchical cluster analysis with species abundance delineated to the four main groups; three abandoned channel groups and one main channel group. Non-metric multidimensional scaling (NMDS) showed that fish community structures of each study site differed from environmental factors: former channel fish communities were positively related to in-stream vegetation cover, whereas main channel fish communities were positively associated with dissolved oxygen and conductivity. The results indicated that channelization, where there was a separation between the former channel and the main channel, had detrimental effects on fish community structures of both the main channel and the abandoned channel in the Mangyeong River. In conclusion, this study suggested that the connectivity between the main channel and abandoned channel were required to enhance both habitat structural diversity and species diversity of the Mangyeong River.

• Korean Journal of Ecology and Environment
• /
• v.39 no.2 s.116
• /
• pp.178-186
• /
• 2006

Community structures of fish in six small eutrophied lakes, located in Gyeonggi province, Korea were investigated from September 2003 to August 2004. Total number of fish species was 33 species of 13 families in which five Korean endemic species such as Rhodeus uyekii, Squalidus gracilis majimae, Abbottina springeri, Iksookimia koreensis, and Odontobutis interrupta were found. Dominant species in the lakes was Hemiculter leucisculus. Both Zacco platypus and Pseudorasbora parva were numberous as subdominant species. In particlilar, Micropercops swinhonis known as partly distributed in the Jeonlabukdo was first recorded in Lake Wangsong and Heungbu which are located in the Gyeonggi province. In lake Myukwoo, Wangsong, and Heungbu, the proportion of Pelagic and omnivorous fish were high, reflecting that fish habitat is poor. A CPUE based fish production was the lowest in Lake Geumgwang of which lake is relatively favorable, whereas it was higher in eutriphied lakes suchs as Dukwoo, Myukwoo and Heungbu lakes.

• Korean Journal of Environment and Ecology
• /
• v.23 no.5
• /
• pp.381-391
• /
• 2009

This is the study of the effects and changes on the ichthyofauna and fish community in Jeonju-cheon stream (located in Jeonju Cit, Jeollabuk-do, South Korea) after the implementation of the Natural Stream Restoration Project. The restoration of the stream was carried out between April 2000 and December 2002, and it covered the mid-section of the stream starting from the upstream of Hanbyeok Bridge down to Samcheon where branches of water join. It is 7.2 km long and passes through the downtown area. In this study, comparisons were made before and after the restoration. Before the restoration (1975 to 1999), the number of fish species collected from the Jeonju-cheon stream turned out to be 12 to 18 species, whereas after the restoration (2003 to 2008), it increased up to 34 species in total. Especially in the case of the middle and downstream sections running across the central regions of the city (Daga Bridge to Seosin Bridge), the number of fish species significantly increased from 5 species to 22 species. Such a dramatic increase of fish species appears to be directly related to the restoration of the stream which was designed to improve the quality of water by preventing polluted sewage water from running into the stream. Besides, the structure of stream bed which became more diversified into various components such as marshes and shallows, as well as rocks, Pebbles, sand and clay, also contributed to the increase of fish species.