• 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.

• Korean Journal of Ichthyology
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• v.36 no.2
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• pp.182-187
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• 2024

Feeding habits of the large yellow croaker, Larimichthys crocea, was studied using 816 specimens collected by large pair-trawl fishery from June 2021 to May 2022 in the coastal waters of Jeju Island, Korea. The range of total length was 19.8~57.4 cm. Using the IRI, Pisces were mainly prey component constituted 57.5%. Euphausiacea and Macrura were important prey component constituted 23.2% and 18.7%, respectively. There was a significant difference in the change in diet composition by size group. As the L. crocea grew, the feeding rate of Euphausiacea decreased and the feeding rate of Pisces increased. There were also significant differences in the changes in diet composition by seasonal group. The most important prey species for L. crocea in the winter and spring were Pisces, in the summer it was Macrura, and in the fall it was Euphausiacea. As a result of analyzing the feeding relationship between size groups and season groups, L. crocea showed significant differences in the interaction between size groups and season groups.

• Applied Microscopy
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• v.16 no.2
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• pp.25-34
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• 1986

The endocrine cells of the stomach and duodenum of the pond tortoise (Amyda sinensis) have been studied by electron microscopy. At least six types of endocrine cells could be identified in these regions. Type I cells were characterized by having pleomorphic or medium sized granules ($100{\sim}430nm$ in diameter, mean; 290 nm) which were moderate in electron density. Type II cells were characterized by having pleomorphic or medium sized granules ($190{\sim}430nm$ in diameter, mean; 280 nm) which were high in electron density. Type III cells were characterized by having large oval or irregular granules($170{\sim}650nm$, mean: 430 nm) with wide vesicular halo which were high in electron density. Type IV cells were characterized by having round or medium sized granules($140{\sim}370nm$, mean; 240 nm) which were low to moderate in electron density and showed a very thin halo. Type V cells were characterized by having large round or oval granules($300{\sim}600nm$, mean; 410 nm) which were low to moderate in electron density and showed a dense core and a wide clear halo. Microfilaments were also found in the cytoplasm. Type VI cells were characterized by having round and small granules($100{\sim}220nm$, mean; 160 nm) which were low to moderate in electron density and showed a very thin halo or crystalline structure of the contents. Many microfilament bundles were also found in the cytoplasm.

• Proceedings of the Korean Aquaculture Society Conference
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• 2006.05a
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• pp.251-252
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• 2006

• The Korean Journal of Zoology
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• v.33 no.1
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• pp.22-27
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• 1990

The gastro-endocrine cells were examined in the fundic region of stomach of the frog, Rana rugosa, by transmission electron microscope. In the present paper, at least three kinds of cell type distributed in this region were idendfted according to their morphological charactedstics based on the size, shape and electron density of the secretory granules. Type I cells were characterized by the presence of round or oval granules (300-5OOnm in diameter) with high electron density. The granules showed a wide lucent between the contents and the limiting membrane. This cell was reminiscent of the ECL cell in the human alimentary mucosa. Type II cells were characterized by the presence of spherical or oval granules (11O-230nm in diameter) with low or high electron density. The granules showed a clear halo between the homogenous contents and the limiting membrane. This cell was reminiscent of the G cell in the human alimentary mucosa. Type Ill cells were characterized by the presence of elongated oval or pheomorphic granules (50-2OOnm in diameter) with low or moderate electron density and abundant microfilament bundles in the cytoplasm. The granules contained a very thin halo.

• Korean Journal of Ichthyology
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• v.11 no.2
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• pp.191-197
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• 1999

Stomach contents of hairtail, Trichiurus lepturus collected in the Nakdong River Estuary were examined quantitatively. T. lepturus was a carnivore which consumed mainly fishes, crustaceans (such as copepods, euphausiids and shrimps) and chaetognaths. Its diets included small quantities of small squids. T. lepturus showed ontogenetic progression of three feeding stages : an initial feeding stage was a planktivorous stage in which copepods were the major food item, followed by a mixed feeding stage in which euphausiids, mysids, shrimps, chaetognaths and fishes were the major food items, and finally a piscivorous stage in which fishes were the major food item. Especially anchovies were heavily selected by large T. lepturus.

• Korean Journal of Ichthyology
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• v.29 no.4
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• pp.267-271
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• 2017

Diel changes in feeding activity of juvenile Pacific herring, Clupea pallasii were investigated throughout the analysis of stomach contents of 301 fishes collected from the southeastern coast of Korea. Fish samples were collected every 3 hour over a 24 h period in summer using small bottom trawl. The ratio of empty stomach, stomach fullness, stomach contents index (SCI) and stomach fullness index (IF) of juvenile C. pallasii were varied markedly with day/night changes. The ratio of empty stomach tended be higher during nighttime, while the other values were higher at daytime, with showing peak before sunset. During daytime, the stomach contents mainly were made up of copepods and euphausiids, while the diets at midnight were composed of nearly digested and unidentifiable items.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.31 no.6
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• pp.806-812
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• 1998

Feeding habits of juvenile Takifug niphobles collected from the eelgrass bed in Kwangyang Bay were studied. T. niphobles (2$\~$8 cm SL) was a carnivore which consumed mainly amphipods (gammarid and caprellid amphipods), crabs, shrimps and gastropods. Its diets included minor quantities of polychaetes, copepods, tanaids and isopods. T. niphobles showed ontogenetic changes in feeding habits. Small individuals preyed mainly on gammarid amphipods, caprellid amphipods and gastropods. However, crabs and shrimps were heavily selected with increasing fish size.

• Korean Journal of Ichthyology
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• v.32 no.2
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• pp.103-109
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• 2020

The diet composition of whitespotted conger, Conger myriaster was studied using 129 specimens collected in the coastal waters Geoje, Korea from June 2018 to May 2019. The size of the specimens ranged from 11.5~22.9 cm in preanus length (AL). C. myriaster was a piscivore that consumes mainly pisces such as Engraulis japonicus and Gobiidae (%IRI: 98.4%). Of the fish species E. japonicus was the most preferred prey. Based on these results, it is considered that Conger myriaster has a characteristic of feeding on abundant prey organisms in the study area. The dietary compositions of C. myriaster was not significantly different among size classes. These results are considered to be due to a lack of specimens and the various size groups were not collected. Based on these results, it is thought that immature fishes inhabit the coast of Geoje. As body size of C. myriaster increased the mean weigh of prey per stomach (mW/ST) tended to increase (one-way ANOVA, P<0.05).

• Korean Journal of Environmental Biology
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• v.33 no.3
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• pp.338-344
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• 2015

In an effort to restore the amphibians in urban freshwater system the characteristics of feeding activity of Rana rugosa living in Gyeonggi-provinces (Yangpyeong-gun and Namyangju-si) was analyzed from 2013 to 2014. The stomach contents of R. rugosa was analyzed non-invasively and compared to organisms captured by sweeping and trapping in their habitat. As a result, Hymenoptera and Cleoptera were primarily preyed by R. rugosa. Particularly, the proportion of Formicidae was more than 98% among the preyed Hymenoptera. Trapped insects in the habitat of R. rugosa's in Namyangju were Hymenoptera (58%, Formicidae 99%), Collembola (17%), Orthoptera (10%) and Diptera (9%) in order in order. In Yangpyeong, trapped insects were Collembola (49%), Orthoptera (14%), Arachnida (9%), Diptera (9%), Cleoptera (7%) and Hymenoptera (3%). Even though Hemiptera and Diptera species are abundant in the streamside zones, R. rugosa could easily hunt Formicidae or Coleoptera on rocks or grassland at streamside. R. rugosa consume small sized ground-insects that are easily found rather than searching for the specific prey. Prey resource of urban stream may be not a limiting factor of R. rugosa inhabitation.