• Korean Journal of Ichthyology
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• v.35 no.3
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• pp.177-182
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• 2023

Total 158 Conger myriaster were examined and the range of Preanal length (PaL) was 8.2~40.1 cm and average Preanal length was 17.3 cm. Proportion of the empty stomach was 30.4% and individuals, which the prey items were found in stomach, were 110. The most important prey component in the diets of C. myriaster was Pisces that constituted 54.4% in %IRI (Index of relative importance). Engraulis japonicus was the most important prey component in Pisces. Macrura was the second largest prey component and Crangon hakodatei was the most important prey component in Macrura. The result of analysis in ontogenetic changes significantly exhibited among three size classes (<15.0 cm, 15.0~20.0 cm, ≥20.0 cm). The proportion of Macrura decreased as increasing body size, whereas the consumption of Pisces increased gradually. As body size of C. myriaster increased, the mean weight of prey per stomach (mW/ST) increased (one way-ANOVA, P<0.05).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.1
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• pp.107-111
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• 2020

In this study, we examined the maturation and spawning of yellowback seabream Dentex tumifrons using samples collected by monthly bottom trawling in Korean coastal waters from January to December 2018. We analyzed monthly changes in gonadosomatic index (GSI), maturity stage, histology, fecundity, and total length at group maturity. Spawning occurred in May and October. Fecundity varied with total length as F=1.3754TL^3.2664, with a range of 1,220 to 155,625 eggs per female. At group maturity, 50%, 75%, and 97.5% estimates of female total length were 18.4, 20.5, and 25.3 cm, respectively.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.1
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• pp.67-73
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• 2020

The maturity and spawning of the yellow goosefish Lophius litulon were studied using samples collected monthly from January to December 2018 from the coastal waters of Korea. We analyzed monthly changes in maturity stage, gonadosomatic index (GSI), total length (TL) at 50%, 75%, and 97.5% group maturity, egg diameter and fecundity. The spawning period was from January to June. The size of eggs spawned was between 0.30 to 1.28 mm. Fecundity varied between 328,314 to 1,624,783 eggs. The percentage of sexually mature females estimated from a logistic function was over 50% at 48.67 cm TL, 75% at 56.76 cm TL and 97.5% at 74.89 cm TL.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.57 no.2
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• pp.117-126
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• 2021

Diet composition and trophic level of Trachurus japonicus were studied using 417 specimens collected by trawls, set nets and purse seine fisheries from March 2019 to February 2020 in the South Sea of Korea. The size of T. Japonicus ranged from 7.0 to 49.8 cm in total length. T. japonicus were a carnivore that fed mainly on euphausiids and pisces. In eddition, T. japonicus fed on small quantities of cephalopods, crabs etc. T. japonicus showed ontogenetic changes in feeding habits. The proportion of euphausiids decreased inversely proportional to body size whereas the consumption of pisces gradually increased. As body size of T. japonicus increased the mean number of prey per stomach and the mean weight of prey per stomach tended to increase, but the mean number of prey per stomach was not significantly different. As a result of the feeding strategy analysis, T. japonicus were specialized feeders with pisces and euphausiids as their dominant prey. The trophic level ranged between 3.57 ± 0.54 and 3.91 ± 0.65, and increased asymptotically with size of specimens. The average trophic level of the T. japonicus was 3.79 ± 0.61.

• 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).

• Journal of the Korean Society for Marine Environment & Energy
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• v.16 no.3
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• pp.217-225
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• 2013

It is time to develop new renewable energy that could fundamentally replace fossil fuel, which has been increasingly needed due to environmental pollution and energy security. Korean marine bio-energy development project is planned to produce 50% of total bioenergy. This study attempts to measure the greenhouse gas emission reduction benefits of marine bio-energy development project through contingent valuation method. Single bounded dichotomous choice (SBDC) is applied with spike model. The results show that the average willingness to pay are estimated to be KRW 4,190 at SBDC, per household per year. If the result has been expanded to the region which is survey conducted, KRW 50.1 billion annually. These quantitative information can be usefully utilized in the cost benefit analysis to implement project and policy-making for the industrialization of marine bio-energy development project.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.46 no.1
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• pp.1-9
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• 2013

Fisheries' biological resources were considered public resources before the 1990s. Every country could access and use these resources without regulation. However, the United Nations adopted the Convention on Biological Diversity and the privileges and rights to these resources were attributed to countries. This research starts with the research background and social and academic value of "The Jasan Eobo (or Report on Marine Organisms in the Coastal Waters near Heuksan Island)" by Jeong Yak-Jeon, who pioneered the new field of Fisheries Science and Marine Biology in Korea in the early 1800s. We also searched for recent results from the Marine Bio-Diversity Research Activities of the Korean National Council for Conservation of Nature (KNCCN) and the Ministry of Maritime Affairs and Fisheries (MOMAF). KNCCN reported that marine bio-diversity comprised approximately 6,500 species in 1996, and the Ministry of Maritime Affairs and Fisheries reported there were about 10,000 species in 2007. Among these marine species, plankton account for about 25%, seaweeds 11%, invertebrates 52%, and vertebrates 12% in Korean Coastal Areas. The Ministry for Food, Agriculture, Forestry, and Fisheries (MIFAFF) enacted a law for Agriculture and Fisheries Resources Management in 2012; this law includes the preservation of marine ecosystems, the conservation of wetlands and the preservation of fisheries resources, and describes the boundary of taxonomy for new species and unknown species that could be identified in the near future. To follow the new regulation for Access to General Resources and Benefit-Sharing, this research suggests (1) the importance of taxonomy for new species and unknown species as a goal of "No Name = No Information", (2) integrated research on bio-diversity, species distributions and the abundance of fisheries resources, both in local areas and in Korean Coastal Areas, and (3) the observance of international regulations or agreements for benefit-sharing without additional damage in the future.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.43 no.5
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• pp.437-444
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• 2010

Extracts of the marine microalgae Nannochloropsis oculata were obtained using 80% methanol (MeOH) and water. The 80% MeOH extract was further fractionated with n-hexane, chloroform, ethyl acetate (EtOAc), n-butanol (n-BuOH), and water to isolate the active fraction. Seven samples were prepared and their angiotensin converting enzyme (ACE), $\alpha$-glucosidase, and cancer cell growth inhibitory activities in vitro were determined. The most profound ACE inhibitory activity was observed in the chloroform fraction, while the others had moderate effects. By contrast, greater $\alpha$-glucosidase inhibitory activity was found in the EtOAc fraction, n-hexane fraction, and water extract of N. oculata. The antiproliferative effects of the extracts and fractions against HL-60, U937, CT-26, and SK-Hep1 cancer cells were also determined. The n-BuOH fraction had the strongest antiproliferative effects on CT-26 cells in a time-dependant manner (P<0.05). These results suggest that the extracts and fractions from N. oculata could be used as a potential functional food or as pharmaceutical ingredients.

• Fisheries and Aquatic Sciences
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• v.18 no.2
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• pp.211-220
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• 2015

We investigated the differences in the expression of the neurohormones kisspeptin (Kiss) and gonadotropin-inhibitory hormone (GnIH) and cytochrome P450 aromatase (P450arom), gonadotropin hormones (GTHs), and sex steroids in the goldfish Carassius auratus exposed to light-emitting diodes (LEDs). The expression levels of Kiss1, Kiss2, G-protein-coupled receptor 54 (GPR54), GTHs, GnIH, and P450arom were compared between the control (white light) and LED-treated goldfish. Furthermore, we measured the plasma levels of follicle-stimulating hormone (FSH) and luteinizing hormone (LH). The levels of Kiss1 mRNA and protein; Kiss2, GPR54, and $GTH{\alpha}$ protein; GTH mRNA; and plasma FSH and LH in the hypothalamus and cultured hypothalamus cells were significantly higher in the green and purple LED treatment groups than in the other groups. These results suggested that red LEDs inhibit the sex maturation hormones, Kiss, GPR54, GTHs, and P450arom, and that GnIH plays a role in the negative regulation of reproductive function in goldfish.

• Journal of Microbiology and Biotechnology
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• v.26 no.6
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• pp.1067-1076
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• 2016

The gene encoding lipase (Lip98) from Aeromicrobium sp. SCSIO 25071 was cloned and functionally expressed in Escherichia coli. Lip98 amino acid sequence shares the highest (49%) identity to Rhodococcus jostii RHA1 lipase and contains a novel motif (GHSEG), which is different from other clusters in the lipase superfamily. The recombinant lipase was purified to homogeneity with Ni-NTA affinity chromatography. Lip98 showed an apparent molecular mass of 30 kDa on SDS gel. The optimal temperature and pH value for enzymatic activity were recorded at 30℃ and 7.5, respectively. Lip98 exhibited high activity at low temperatures with 35% maximum activity at 0℃ and good stability at temperatures below 35℃. Its calculated activation energy was 4.12 kcal/mol at the low temperature range of 15-30℃. Its activity was slightly affected by some metal ions such as K⁺, Ca²⁺, and Na⁺. The activity of Lip98 was increased by various organic solvents such as DMSO, ethanol, acetone, and hexane with the concentration of 30% (v/v) and retained more than 30% residual activity in neat organic solvent. The unique characteristics of Lip98 imply that it is a promising candidate for industrial application as a nonaqueous biocatalyst and food additive.