• Korean Journal of Ichthyology
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• v.35 no.3
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• pp.207-210
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• 2023

While an investigation on the old samples kept at collection room in National Institute of Fisheries Science (NIFS), we found a unique single specimen of burbot, Lota lota (54.7 cm in standard length) from Amnokgang River, North Korea on 14 April 1935. Burbot is the only stream dweller among members of the Gadiformes and found in the northern parts of Eurasia and North America. There was a little information in Korea, because it inhabits only the northern part of North Korea. This species is easily distinguished by having two dorsal fins, one anal fin, a barbel, and posterior of caudal fin rounded. This study provides detailed morphological characteristics and compares it with those of previous literatures on the North Korean L. lota.

• Journal of Life Science
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• v.29 no.4
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• pp.428-435
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• 2019

Alaska pollock (Gadus chalcogrammus) is a marine fish species belonging to the family Gadidae. In this study, whether the Alaska Polloack Roe have antioxidant properties, 2,2-diphenyl-1 picrylhydroazyl (DPPH), hydroxyl radical (OH) reducing activity, and nitric oxide radical (NO) scavenging activity were evaluated in distilled water extract (DWE) and ethanol extract (ETE) of raw Alaska pollock roe, Gochujang Pollock roe, and fermented seasoned Pollock roe. The DPPH scavenging activity of the DWE with Gochujang Pollock roe was 71.9% at a concentration of 1.0 mg/ml and that of the ETE was 73.7% at the same concentration. The DPPH scavenging activity of the DWE with fermented seasoned Pollock roe was 78.0% at 1.0 mg/ml, whereas that of ETE was 78.4% at the same concentration. The $IC_{50}$ values of the DWE and ETE of raw Pollock roe for DPPH were $11.65{\mu}g/ml$ and $11.47{\mu}g/ml$, respectively. The OH scavenging activities of raw Pollock roe, Gochujang Pollock roe, and fermented seasoned Pollock roe ethanolic extracts at a concentration of 1.0 mg/ml were 70.9%, 79.0, and 80.6%, respectively. The $IC_{50}$ values of the DWE and EWE of raw Pollock roe for NO were $11.45{\mu}g/ml$ and $11.41{\mu}g/ml$, respectively. The DPPH, OH, and NO scavenging abilities in DWEs and ETEs of Gochujang and fermented seasoned Pollock roe were higher than those of instant (no Gochujang or season treatment) treatment Pollock roe. Both the Gochujang and fermented seasoned Pollock roes have natural radical scavenging ability and may be useful potential antioxidant food supplements.

• Journal of Marine Life Science
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• v.7 no.1
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• pp.52-54
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• 2022

Mitochondrial genomes of three specimens of Gadus chalcogrammus Pallas 1,814 from Korea and Japan were completely analyzed by the primer walking method. They were 16,570~16,571 bp in length, each comprising 13 protein-coding genes, two ribosomal RNA genes, and 22 transfer RNA genes. Their gene orders were identical to those of conspecific specimens, but exhibited unique haplotypes. In the phylogenetic tree, the juvenile Korean and adult Japanese specimens were separated from the dominant clade composed of specimens from Japan, Korea, the Bering Sea, and the Arctic, including the adult Korean specimen.

• Korean Journal of Ichthyology
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• v.29 no.1
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• pp.62-68
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• 2017

The Alaska pollock (Gadus chalcogrammus) belongs to the family Gadidae; it is a cold water fish, and has been developed as a novel aquaculture species in Korea. In this study, we describe ongoing surveillance for aquatic animal pathogens based on growth stages. We investigated bacterial flora in rearing water, and monitored pathogens; we also analyzed histopathological traits of abnormal fish. In rearing water, the total bacterial counts were $2.1{\times}10^3cfu/mL$ and Vibrio spp. (52%) were predominant in the larvae stage. In the juvenile and adult stages, the total bacterial counts were $3.4{\times}10^3$ and $3.2{\times}10^2cfu/mL$, respectively (with Pseudomonas sp. as the predominant species; 90% and 52%). This result revealed that the bacterial flora in rearing water changed depending on the feeding types. No virulent-bacteria or problematic viruses (VHSV, viral hemorrhagic septicemia virus; NNV, nervous necrosis virus; MBV, marine birnavirus) were detected from outwardly healthy fish using either culture or PCR assay. Some juveniles (less than 5%) had gas bubbles on the gill lamellae, degeneration of the corneal epithelium, and choroid gland degeneration, suggesting that these symptoms were caused by external injury and secondary infection by opportunistic bacteria. Disease management is important to cope with disease emergence in the novel aquaculture species Alaska pollock.

• 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.

• Journal of Marine Life Science
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• v.8 no.2
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• pp.160-165
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• 2023

This study describes the light microscopical cell types and histochemical characteristics as a preliminary study for the research on integument of the walleye pollock Gadus chalcogrammus in accordance with the physiological and environmental changes. The lateral line of the integument surface showed a curve in the anterior part and was straight from the middle to the posterior part. Integument is composed of outer epidermis and inner dermis. The epidermis is a stratified layer composed of epithelial cells, mucous cells, and club cells. Epithelial cells are classified into squamous superficial cell, cuboidal intermediated cell and columnar basal cell. The thickness of epidermis was 122.9 ㎛, and the ratio of epidermis thickness to body length was 0.03%. The mucous cell and club cell of unicellular gland were mainly distributed in the apical and middle layer of epidermis. The mucous cell contained mucosal materials of acidic glycoprotein. The proportion of mucous cells and club cells were 21.3 (± 7.0)% and 4.0 (± 1.0)% of epidermal area, respectively. The dermis was dense connective tissue layer and composed of mainly collagen fibers. It also contained fibrocytes, blood vessels, melanophores and scales.