• Korean Journal of Ichthyology
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• v.34 no.2
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• pp.102-112
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• 2022

This study investigated dietary habits and intra- and inter-specific food resource partitioning of co-occurring walleye pollock (Gadus chalcogrammus) and Pacific cod (G. macrocephalus) from the waters off the north-eastern coast of South Korea using stomach contents and stable isotopes (δ¹³C and δ¹⁵N) analyses. Both species are mesopelagic carnivores that consumed mainly benthopelagic crustaceans, but teleosts were also abundant in the diet of Pacific cod. Non-metric multidimensional scaling (nMDS) ordination and permutational multivariate analysis of variance (PERMANOVA) of dietary data revealed significant intra- and inter-specific dietary differences, i.e., food resource partitioning. Nitrogen stable isotope values (δ¹⁵N) were similar between walleye pollock and Pacific cod, but carbon stable isotope values (δ¹³C) were significant different, suggesting different trophic positioning. Canonical analysis of principal coordinate (CAP) ordination plot further demonstrated that differences in the type and range of prey ingested by the two species contributed such an inter-specific difference in the diet compositions. Ontogenetic changes in diet compositions were evident. As walleye pollock, they preyed more upon carid shrimps and cephalopods, but no such trend was observed in the diets of Pacific cod. While stable isotope values indicated that large-sized specimens of both species were significantly enriched in ¹⁵N relative to smaller conspecifics thus supporting these data. Consequently, in this study, both methodologies, i.e., stomach contents and stable isotope analyses, provided evidence of inter- and/or intra-specific dietary segregations and trophic niche partitioning between co-occurring walleye pollock and Pacific cod off eastern Korean waters.

• Development and Reproduction
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• v.16 no.4
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• pp.301-307
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• 2012

Olive flounder Paralichthys olivaceus is one of the most widely cultured fish species in Korea. Although olive flounder receive attention from aquaculture and fisheries and extensive research has been conducted eye morphological change in metamorphosis, but little information was known to molecular mechanism and gene expression of eye development- related genes during the early part of eye formation period. For the reason of eyesight is the most important sense in flounder larvae to search prey, the screening and identification of expressed genes in the eye will provide useful insight into the molecular regulation mechanism of eye development in olive flounder. Through the search of an olive flounder DNA database of expressed sequence tags (EST), we found a partial sequence that was similar to crystallin beta A1 and gamma S. Microscopic observation of retinal formation correspond with the time of expression of the crystallin beta A1 and gamma S gene in the developmental stage, these result suggesting that beta A1 and gamma S play a vital role in the remodeling of the retina during eye development. The expression of crystallin beta A1 and gamma S were obviously strong in eye at all tested developing stage, it is also hypothesized that crystallin acts as a molecular chaperone to prevent protein aggregation during maturation and aging in the eye.

• Journal for History of Mathematics
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• v.26 no.2_3
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• pp.197-210
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• 2013

The late 18C Malthus studied population growth for the first time, Verhulst the logistic model in 19C and, after that, the study of the predation competition between two species resulted in the appearance of Lotka-Volterra model and modified model supported by Gause's experiment with bacteria. Instable coexistence equilibrium being found, Solomon and Holling proposed functional and numerical response considering limited abilities of predator on prey, which applied to Lotka Volterra model. Nicholson and Baily, considering the predation between host and parasitoid in discrete time, made a model. In 20C there were developed various models of disease dynamics with the help of mathematics and real data and named SIS, SIR or SEIR on the basis of dynamical phenomena.

• Journal of Korean Society on Water Environment
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• v.23 no.3
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• pp.339-347
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• 2007

Zooplankton community dynamics were studied after establishment of an artificial vegetation island (AVI) in Lake Paldang, from April 2005 to November 2006. There were distinct seasonal and inter-annual changes of total zooplankton abundance at the survey site. Total zooplankton abundance rapidly increased in spring and fall, while it remained low throughout winter. During summer, the dynamics of zooplankton community seemed to be largely affected by hydrological parameters such as, precipitation and inflow. Total zooplankton abundance and biomass below AVI was much higher than that of pelagic zone (L1) in Lake Paldang. Copepoda and cladocera represented the main bulk of the zooplankton community from summer to fall at the both sites. Copepods were more dominant at AVI area, while cladocera were more dominant at pelagic zone (L1). Water quality, prey and habitat condition, species competition between zooplankton seemed to play important roles in dominance of the copepoda and cladocera in zooplankton community at AVI area. Our results conclude that artificial vegetation island provide the stable habitat and besides phytoplankton, diverse food to zooplankton, and consequently influence the diversity and richness of zooplankton community.

• Korean Journal of Ichthyology
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• v.24 no.4
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• pp.272-277
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• 2012

The feeding habits of black scraper, Thamnaconus modestus, were studied using 172 specimens collected in the coastal waters of Geomun-do, Korea. The size of the specimens ranged from 16.2 to 39.1 cm in standard length (SL). T. modestus was a omnivore that consumes mainly benthos. Of the benthos species nephtheidae was the most preferred prey. Its diet also includes, algae, thoracica, gastropoda, desmospongia. Small and medium size individuals (<21~33 cm, SL) fed mainly on nephtheidae and algae. Larger individuals (>33 cm, SL) fed mainly on thoracica. The proportion of nephtheidae decreased as body size increased (>33 cm, SL), whereas the consumption of thoracica gradually increased.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.20 no.3
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• pp.230-236
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• 1987

The correlation between tintinnid and dinoflagellate by means of seasonal variation of standing crops was investigated at two selected stations in Masan Bay, well-known as a red tide zone in southern coastal waters of Korea, during the period from January 1981 to December 1982. The most dominant dinoflagellates mainly belonged to $20-60\;{\mu}m$ of size class, and Gymnodinium and Prorocentrum were predominant from spring to summer season. Of tintinnid, Favella spp. were most dominant and associated with dinoflagellate blooms at the same season. Especially, Favella spp. were most positively correlated with $40-60\;{\mu}m$ size class of dinoflagellate, and also represented higher multiple corrleation with outer station (St.2), comprising relatively large species of Gymonodinium and Protogonyaulax, than with inner station (St. 1), dominated by Prorocentrum blooms. Thus, the interspecific food selection by size and morphology between tintinnid including Favella and dinoflagellate is recognized and it is considered to be an important factor influenecing on the prey-predator relationship in lower trophic level in the surveyed area.

• Korean Journal of Ichthyology
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• v.24 no.1
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• pp.20-26
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• 2012

The feeding habits of john dory, $Zeus$ $faber$, were studied using 462 specimens collected in the coastal waters of Geomun-do, Korea. The size of the specimens ranged from 7.8 to 40.2cm in standard length (SL). $Z.$ $faber$ was a piscivore that consumes mainly teleosts such as $Trichiurus$ $lepturus$, $Scomber$ $japonicus$, $Callanthias$ $japonicus$ and $Trachurus$ $japonicus$. Of the fish species $T.$ $lepturus$ was the most preferred prey. Its diet also includes cephalopods, shrimps and euphausia. Smaller individuals (<15 cm SL) fed mainly on fishes and cephalopods. The proportion of cephalopods decreased as body size increased, whereas the consumption of fishes gradually increased. Fishes accounted for almost stomach contents of larger individuals (more than 15 cm SL).

• Korean journal of applied entomology
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• v.39 no.2
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• pp.59-71
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• 2000

The Asian ladybird, Harmonia axyridis, might be distinguished in biological control agents for the several aphid species in the greenhouses as well as in the fields. Therefore, feeding behavior and predacious capability characteristics were observed. When ladybirds are searching for aphids as their preys, they use the maxillary palpus as contact reception. Otherwise, most of aphids escape from walking or chewing ladybird to other place (mainly move to near-by leaf, or fall down to the under-leaf or ground) instead of plant sucking. Consumed time of ladybirds for searching and feeding prey were significantly different and dependent on their development stage. The ladybird adults ate about 120 green peach aphids and 257 cotton aphids per day. The 3rd instar of ladybirds ate 2,420 and 2,750 eggs of greenhouse whitefly on the cucumber and tomato leaf, respectively, as well. However, ladybird instars taken greenhouse whitefly eggs could not continuously develope to adult, on the other hand, ladybirds taken aphids were normal condition.

• Korean Journal of Ichthyology
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• v.25 no.3
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• pp.163-168
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• 2013

Two flatfish species were collected between January 2010 and August 2010 from fishing vessels operating with fishing, gill net and shrimp trawls along the coastal waters off Tongyeong, Korea in order to examine feeding habits. Kareius bicoloratus fed mainly on bivalves and fishes, whereas Clidoderma asperrimum fed mainly on ophiuroids. Our feeding strategy graphical method reveled that K. coloratus and C. asperrimum were specialist predator, with a narrow niche width.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.44 no.3
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• pp.284-289
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• 2011

The feeding habits of the blackthroat seaperch Doederleinia berycoides were studied using 650 specimens collected in the Southern Sea of Korea, from January to December, 2005. The size (standard length, SL) of the specimens ranged from 6.3 to 35.2 cm. D. berycoides is a piscivore that consumes mainly teleosts such as Engraulis japonicus, Acropoma japonicum, and Myctophum nitidulum. Of the fish species Engraulis japonicus was the preferred prey. D. berycoides also eats small quantities of shrimps, amphipods, euphausiids, mysids, and crabs. D. berycoides showed ontogenetic changes in its feeding habits. Smaller individuals (5-10 cm SL) fed mainly on shrimp. The proportion of shrimp decreased with increasing fish size, and this decrease paralleled the increased consumption of fish. Fish accounted for almost all of the stomach contents of individuals larger than 15 cm SL. Cluster analysis based on the percentage dry weight (%DW) identified two size groups: group A (<15 cm SL) consumed primarily shrimp and fish; and group B (15< cm SL) preyed exclusively on fish. There was little seasonal change in the diet of D. berycoides, but shrimp constituted 41.8% of the summer diet in %W.