• Journal of Environmental Impact Assessment
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• v.21 no.6
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• pp.841-857
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• 2012

Preliminary ecological environmental assessments including physico-chemical constituents, water quality, fish fauna analysis, physical habitat health, and ecological health assessment were conducted as a primary step for Jeungchon micro-habitat ecosystem restoration in 2012. Water chemistry analysis of conductivity, dissolved oxygen, chlorophyll-a and etc. indicated that there were no significant differences(p < 0.05) among 6 sites between the headwaters and downstream. Multi-metric model analysis of Qualitative Habitat Evaluation Index(QHEI) showed that brooklets were at "good condition" as a mean QHEI of 158.7(n = 6) and the longitudinal differences of the model values between the sites were minor(QHEI range: 153 - 165). Total fish species and the number of individuals were 12 and 481, respectively, and dominant species were Zacco platypus(49.5%) and Zacco koreanus(36.8%). Tolerance guild analysis showed that the proportion of sensitive species($S_S$) had a negative linear function[$S_S=86.35-0.31(D_H)$; $R^2$ = 0.892, p < 0.01] with a distance from the headwaters, while the proportion of tolerant species($T_S$) had a positive linear function($R^2$ = 0.950, F = 90.28, p < 0.001) with the distance. Trophic feeding guild analysis showed that the proportion of insectivore species($I_n$) had a negative linear function($R^2$ = 0.934, p < 0.01) with a distance from the headwaters, while the proportion of omnivore species($O_m$) had a positive linear function($R^2$ = 0.958, p < 0.001) with the distance. Index of Biological Integrity(IBI) model, based on fish assemblages, showed a "fair condition" as a mean IBI of 23(n = 6), and there was a distinct differences of ecological health between the headwaters(S1 = 30; "good condition") and the downstreams(S6 = 14; "poor condition"). Overall, the preliminary environmental impact assessments suggest that water quality, physical habitat conditions(QHEI model), and ecological health(IBI model) were maintained well, even if the state was not an excellent conditions.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.1
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• pp.73-79
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• 2021

The feeding habits of Chub mackerel Scomber japonicus were investigated using 329 specimens collected from coastal waters of the South Sea of Korea. S. japonicus is mainly a piscivore, consuming small fish such as Engraulis japonicus (%RI: 81.0 %). The diet of Chub mackerel also includes small quantities of thaliaceans, euphausiids, and amphipods. We calculated the trophic level as 3.92 for S. japonicus. The dietary composition of S. japonicus did not show significant differences with size, but differed with season. As the body size of S. japonicus increased, the mean weight of prey within the stomach (mW/ST) increased (One-way ANOVA, P<0.05).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.6
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• pp.1052-1057
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• 2021

The diet composition of common flying squid Todarodes pacificus was studied using 1,084 specimens collected through trawl and jigging from June 2018 to June 2020 in the East Sea of Korea. The mantle length (ML) of the collected individuals ranged from 13.6 to 31.1 cm. Todarodes pacificus is a carnivore. In the study area, T. pacificus was observed feeding mainly on fish and cephalopods, in addition to small quantities of crustaceans. The calculated trophic level value for T. pacificus was 4.10. Small individuals (ML, <18.0 cm) mainly fed on cephalopods, while intermediate (ML, 18.0-23.0 cm) and large (ML, ≥23.0 cm) individuals fed mainly on fish and occasionally on cephalopods. Overall, as the body size of T. pacificus increased, the mean weight of the consumed prey increased (one-way ANOVA, P<0.05).

• ALGAE
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• v.38 no.2
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• pp.111-126
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• 2023

Mixotrophic dinoflagellates act as primary producers, prey, and predators in marine planktonic food webs, whereas exclusively autotrophic dinoflagellates are primary producers and prey. Species of the dinoflagellate genus Scrippsiella are commonly found in marine ecosystems and sometimes cause harmful red tides. Among the 28 formally described Scrippsiella species, S. acuminata has been found to be mixotrophic and two unidentified species have been found to be mixotrophic. To determine whether the other species in this genus are similarly mixotrophic, the mixotrophic ability of S. donghaiensis SDGJ1703, S. lachrymosa SLBS1703, S. masanensis SSMS0908, S. plana SSSH1009A, and S. ramonii VGO1053 was explored using 15 potential prey items, including 2-㎛ fluorescently labeled microspheres (FLM) and heterotrophic bacteria (FLB), the cyanobacterium Synechococcus sp., and various microalgal prey species. The ability of S. acuminata to feed on FLM and FLB was also investigated. We found that S. donghaiensis, S. lachrymosa, S. masanensis, S. plana, and S. ramonii did not feed on any potential prey tested in this study, indicating a lack of mixotrophy. However, S. acuminata fed on both FLM and FLB, confirming its mixotrophic ability. These results lowered the proportion of mixotrophic species relative to the total number of tested Scrippsiella species for mixotrophy from 100% to 29-38%. Owing to its mixotrophic ability, S. acuminata occupies an ecological niche that is distinct from that of S. donghaiensis, S. lachrymosa, S. masanensis, S. plana, and S. ramonii.

• ALGAE
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• v.38 no.1
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• pp.39-55
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• 2023

Exploring mixotrophy of dinoflagellate species is critical to understanding red-tide dynamics and dinoflagellate evolution. Some species in the dinoflagellate genus Karenia have caused harmful algal blooms. Among 10 Karenia species, the mixotrophic ability of only two species, Karenia mikimotoi and Karenia brevis, has been investigated. These species have been revealed to be mixotrophic; however, the mixotrophy of the other species should be explored. Moreover, although K. mikimotoi was previously known to be mixotrophic, only a few potential prey species have been tested. We explored the mixotrophic ability of Karenia bicuneiformis, Karenia papilionacea, and Karenia selliformis and the prey spectrum of K. mikimotoi by incubating them with 16 potential prey species, including a cyanobacterium, diatom, prymnesiophyte, prasinophyte, raphidophyte, cryptophytes, and dinoflagellates. Cells of K. bicuneiformis, K. papilionacea, and K. selliformis did not feed on any tested potential prey species, indicating a lack of mixotrophy. The present study newly discovered that K. mikimotoi was able to feed on the common cryptophyte Teleaulax amphioxeia. The phylogenetic tree based on the large subunit ribosomal DNA showed that the mixotrophic species K. mikimotoi and K. brevis belonged to the same clade, but K. bicuneiformis, K. papilionacea, and K. selliformis were divided into different clades. Therefore, the presence or lack of a mixotrophic ability in this genus may be partially related to genetic characterizations. The results of this study suggest that Karenia species are not all mixotrophic, varying from the results of previous studies.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.28 no.1
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• pp.105-113
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• 1995

Seasonality in biomass and egg Production was investigated for Calanus sinicus, one of the major copepods in Asan Bay, Korea. Biomass of this species in this restricted embayment showed only one Peak in spring, but e99 Production showed two Peaks, spring (April and May) and fall (September). Average egg Productions during the spawnlng seasons were 16.3 egg/female/day (spring) and 7.6eggs/female/day (fall) with maximum egg Production of 39.0 eggs/female/day. Food concentrations in this bay measured'1 terms of particulate organic carbon (POC) were relatively high around the year, and correlation between egg Production and POC was not significant. With the food Provided sufficiently animals Produced a lot of fecal Pellets, but egg Production was ceased after several days of experiment. From these results it was believed that egg Production in this bay was influenced by food quality and feeding history rather than food concentrations. Habitat temperatures also seem to have influence on egg Production from the tacts that no egg was Produced at extreme habitat temperatures, although the correlation between the two was not significant. In this bay, two generations with different time periods seem to progress yearly. Distribution was coupled with life cycle only at certain time of the year. During the other periods predation pressure by the higher trophic levels and shift of the centers of the distributions toward deeper outer bay seemed to be responsible for the observed distribution and egg Production of this species in this bay. Comparing with the Previous reports, migration of fairly long distance and continual reproduction seemed possible for this species.

• Korean Journal of Environmental Biology
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• v.31 no.4
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• pp.478-485
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• 2013

Fish field survey, especially fish distribution and their ecological characteristics, was performed in the downstream region of Gyeongan stream during the period of before (June) and after (October) the summer monsoon in 2010. Depending on the characteristics of each site, fyke net or casting net was used for fish sampling. Feeding classification was determined by the analysis of stomach contents. Total number of family and species sampled were 5 and 17, respectively. The dominant family was Cyprinidae (12 species), and relative abundance (RA) of the most dominant species, Lepomis macrochirus and Zacco platypus, was 38% and 24%, respectively. Exotic species and Korean endemic species observed were 3 (423 individuals, RA 44%) and 4 (98 individuals, RA 10%), respectively. Tolerance guild analysis as characteristics of ecological indicators revealed an undoubtedly high percentage (97%), compared to others as reflected by the identification of just one sensitive species. Analysis of trophic guilds showed that L. macrochirus dominated among insectivores (44% RA). The food of L. macrochirus composed of, aquatic insects, benthic invertebrates, zooplankton, Chironomidae, and waterweed. Thus, we determined that L. macrochirus could be classified as insectivores (partially carnivores) in this study. Conversely, Z. platypus consumed Cladocera exclusively, greater than 90% of their feed. We presume that stable isotope analysis would identify the exact position of these species in the food web.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.19 no.4
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• pp.302-307
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• 2014

To examine the trophic ecology of the ascidian Styela clava in an aquaculture system of Korea, stable carbon and nitrogen isotopes were analyzed monthly in S. clava, coarse ($>20{\mu}m$, CPOM) and fine particulate organic matters ($0.7<<20{\mu}m$, FPOM). CPOM (means: $-18.5{\pm}1.2$‰, $9.3{\pm}0.7$‰) were significantly higher ${\delta}^{13}C$ and ${\delta}^{15}N$ values than those ($-20.5{\pm}1.5$‰, $8.4{\pm}0.5$‰) of FPOM. S. clava had mean ${\delta}^{13}C$ and ${\delta}^{15}N$ values of $-18.9({\pm}1.7)$‰ and $11.6({\pm}0.7)$‰, respectively. S. clava were more similar to seasonal variations in ${\delta}^{13}C$ and ${\delta}^{15}N$ values of FPOM than those of CPOM, suggesting that they rely largely on the FPOM as a dietary source. In addition, our results displayed that the relative importance between CPOM and FPOM as dietary source for the ascidians can be changed according to the availability of each component in ambient environment, probably reflecting their feeding plasticity due to non-selective feeding irrespective of particle size. Finally, our results suggest that dynamics of pico- and nano-size plankton (i.e., FPOM) as an available nutritional source to S. clava should be effectively assessed to maintain and manage their sustainable aquaculture production.

• Korean Journal of Ichthyology
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• v.34 no.3
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• pp.179-185
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• 2022

The feeding habits of Largehead hairtail Trichiurus japonicus was studied using 377 specimens collected in the Yellow Sea of Korea. The specimens ranged from 4.5 to 33.7 cm in Anal length (AL). T. japonicus consumed mainly a piscivore, such as Engraulis japonicus [percent index of relative importance (%IRI) =74.1%]. We calculated the trophic level as 3.84 for T. japonicus. Fishes were the main prey items for all seasons. The main fish prey during autumn and winter was E. japonicus, whereas those during spring and summer was Larimichthys polyactis. Fishes were the main prey items for all size groups (<15 cm, 15~20 cm, 20~25 cm, ≥25 cm). T. japonicus also showed size-related dietary shift from Spratelloides gracilis and E. japonicus to L. polyactis and T. japonicus. As the anal length of T. japonicus increased, the mean number of preys per stomach (mN/ST) and the mean weight of preys per stomach (mW/ST) tended to increased (One-way ANOVA, P<0.05). Seasonal and size-related shifts in dietary composition were investigated by PERMANOVA analysis, which showed significant variations among size classes and seasons.

• Korean Journal of Environmental Biology
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• v.27 no.3
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• pp.297-305
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• 2009

The Asian paddle crab, Charybdis japonica (A. Milne-Edwards) is an important fishery resource in Korea. Despite its common occurrence and commercial importance, few studies have been carried out on the life cycle and trophic ecology of these populations inhabiting on the tidal flat. Food habits of C. japonica populations were investigated on the Jangbong tidal flat, Incheon, Korea. Monthly samples were taken using a modified otter trawl from November 1999 to January 2001. Based on the examination of stomach contents from 257 individuals, the frequencies of occurrence and the relative volumes of food items were analysed. As a result, the crustaceans (the brachyura, the cirripedia and the harpacticoid copepoda), the echinoderms (the ophiuroidea) and the molluscs (the cephalopoda Loligo beka, the bivalves Bivalvia unid. and Mytilus galloprovincialis) were important food for this species. To examine ontogenetic shifts in diets, individuals of C. japonica were categorized into 2 different size classes (${\leq}60mm$ and ${\geq}61mm$ in carapace width) representing sexually premature and mature stages. The food items of the small crabs (${\leq}60mm$) were dominated by the crustaceans with the harpacticoid copepods constituting 84.6% of total prey number. The next group was the bivalves and the brachyurans. On the other hand, the large crabs (${\geq}61mm$) mainly feed on the bivalvia (Mytilus galloprovincialis and Bivalvia unid.), the brachyurans (Crab unid.) and occasionally the cephalopods and fishes. The difference in proportions of the main prey items among these two size classes was statistically significant. Therefore, the feeding habits of the portunid crab, C. japonica changed with growth.