• The Journal of Fisheries Business Administration
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• v.46 no.1
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• pp.29-39
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• 2015

This study aimed to evaluate the TAC policy and to examine the effective annual TAC quota in the sandfish stock rebuilding plan using a bioeconomic modelling method. In the analysis, first, a sandfish bioeconomic model was developed by combining a sandfish stock population model and economic models by fishery and second, achieving stock rebuilding targets and changes of fishing revenues by the level of annual TAC quota were examined. Model results indicated that the TAC 1,500ton policy would have the greatest impact on the increase of sandfish stock biomass comparing to the status quo and other TAC policies. In addition, it was evaluated that the total fishing revenues of coastal gillnet and danish seine fisheries could be increased the most in the TAC 2,500ton policy. In both cases of TAC 3,500ton and 4,000ton, the fishing revenues of both fisheries were inversely reduced due to the decrease of catch by coastal gillnet and the decline of market prices by danish seine's excessive catch. Furthermore, they would have a negative impact on sandfish stock biomass.

• Journal of Fisheries and Marine Sciences Education
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• v.28 no.6
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• pp.1651-1661
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• 2016

The purpose of this study is to draw up a plan for improving working conditions of distant water fishing vessel crew in order to revitalize the declining distant water fishing industry. Land-based employment has increased as the result of industrialization, which in turn created shortage in marine crew supply for distant water fishing vessels. Pressure on increasing wages for sea farers is put on the industry for this reason, making the labour market in the distant water fishing industry tougher and tighter. Multiple issues have yet to be addressed for distant water fishing vessel crew. They suffer from excessive work compared to other industries. Crew management is another issue, as sea farers face poor labour conditions, working on board vessels in a collective way where no autonomous actions are allowed. Other issues include unqualified crew supply, increasing ratio of labour costs for crew to sales, and intensified implications of labour unions, which are as well making crew supply difficult as a whole. To this end, more well-qualified workers should take part in production operations in the distant water fishery. Both wage increase and working condition improvement should be achieved in order to strengthen motivation towards qualified sea farers. Sustainable crew supply can be achieved when working environments, gender-based working conditions, welfare are prioritized and improved as a whole.

• Journal of Fisheries and Marine Sciences Education
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• v.5 no.2
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• pp.80-89
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• 1993

Notwithstanding Korea and P. R.China are located in the neighborhood each other geographically, the break of diplomatic relations of them continued a long term, and the difference of ideology and social structure of two countries was acting as a barrier to understand each other in many fields. Two countries established formal diplomatic relation in 1992, and then the interchange and mutual cooperation between both countries are being performed rapidly, but the field of fisheries education and research system is continuing in the early stage yet. It can be easily expected that the interchange and mutual cooperation in the field of fisheries through the ocean contribute not only to the international friendship, but to the rational management of fisheries resources. In accordence with the necessity mentioned above, the author considered the general situation of fisheries education and research system in P. R. China. P. R. China runs two kinds of fisheries education system which are regular and irregular system. The regular education system is the principal means of cultivating fisheries scientists and technicians. And there are three grade levels in regular education : the tasks of which are undertaken by the fisheries universities, fisheries colleges and fisheries high schools. Adult education system in fisheries are of the following types : fishery cadet training courses, evening schools, correspondence courses and broadcasting or TV programs. The fisheries research in P. R. China is undertaken by the research institutes under the Bureau of Aquatic Products, and the basic research of oceanography is undertaken by the oceanographic institutes under the Chinese Academy of Science.

• Journal of Ecology and Environment
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• v.43 no.1
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• pp.61-72
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• 2019

Background: Organic carbon stored in coastal wetlands, which comprises the major part of oceanic "blue carbon," is a subject of growing interest and concern. In this study, organic carbon storage in coastal wetlands and its economic value were estimated using the raw data of 25 studies related to soil carbon storage. Data were collected from three tidal flats (one protected and two developed areas) and two estuarine salt marshes (one protected and one restored area). Bulk density, soil organic matter content, and standing biomass of vegetation were all considered, with Monte Carlo simulation applied to estimate the uncertainty. Results: Mean carbon storage in two salt marshes ranged between 14.6 and $25.5kg\;C\;m^{-2}$. Mean carbon storage in tidal flats ranged from 18.2 to $28.6kg\;C\;m^{-2}$, with variability possibly related to soil texture. The economic value of stored carbon was estimated by comparison with the price of carbon in the emission trading market. The value of US $ $6600\;ha^{-1}$ is ~ 45% of previously estimated ecosystem services from fishery production and water purification functions in coastal areas. Conclusions: Although our study sites do not cover all types of large marine ecosystem, this study highlights the substantial contribution of coastal wetlands as carbon sinks and the importance of conserving these habitats to maximize their ecosystem services.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.52 no.5
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• pp.496-510
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• 2019

We investigated the reproductive characteristics of the sweetfish Plecoglossus altivelis, including changes in the gonadosomatic index (GSI), frequency of gonad developmental stages, and abundance of drifting larvae, in three streams (Gangjeong, Yeonoi, and Ongpo) on Jeju Island from May 2004 to December 2005. The GSI values of female P. altivelis in all Jeju streams began to increase in September and reached a maximum in October and November. Peak GSI values in males occurred in Gangjeong from October to November, in Yeonoi from November to January, and in Ongpo from September to October. The gonadal development of P. altivelis was classified into four stages: growth (March to October), maturity (September to December in females; July to December in males), spawning (September to January), and degeneration (October to March in females; after November in males). Drifting larvae were collected from October to January. These results suggest that the main spawning activity of P. altivelis in Jeju streams occurs from October to November. The information about the reproductive characteristics of P. altivelis obtained in this study is critical to fishery management for this species.

• Journal of Species Research
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• v.10 no.1
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• pp.78-85
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• 2021

Heterorhabdus papilliger (Claus, 1863) is newly reported from the Tsushima Warm Current realm of the southern Korean waters. Its morphological diagnostic characteristics generally agreed well with the original description and the previous records of H. papilliger. The female of H. papilliger can be recognized by the genital somite, which in lateral view has a more or less rounded genital prominence and an uninflated posterior ventral margin; the second exopodal segment of male right leg 5 with the medial projection with a large, rounded, plumose proximal lobe, and a poorly developed distal lobe. The genetic difference for the partial mtCOI gene between Korean specimens and H. papilliger from Spain and Japan of the same clade is 0.4%, while the difference between Korean specimens is 0.5%. However, the interspecific difference for the mtCOI gene between H. papilliger from the Korean waters and the other Heterorhabdus species is in the range of 14.7-20.8%, suggesting that the former is a valid species.

• Korean Journal of Remote Sensing
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• v.37 no.1
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• pp.69-84
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• 2021

Awareness of boats is a main issue in areas of fishery management, illegal fishing, and maritime traffic, etc. For the awareness, Automatic Identification System (AIS) and Vessel-Pass System (V-PASS) have been widely used to collect the boat-related information. However, only using these systems makes it difficult to collect the accurate information. Recently, satellite-based data has been increasingly used as a cooperative system. In 2015, U.S. National Oceanic and Atmospheric Administration (NOAA) developed a boat detection algorithm using Visible Infrared Imaging Radiometer Suite (VIIRS) Day & Night Band (DNB) data. Although the detections have been widely utilized in many publications, it is difficult to estimate the night-time fishing boats immediately. Particularly, it is difficult to estimate the threshold due to the lunar irradiation effect. This effect must be corrected to apply a single specific threshold. In this study, the moon phase was considered as the main frequency of this effect. Considering the moon phase, relational expressions are derived and then used as offsets for relative correction. After the correction, it shows a significant reduction in the standard deviation of the threshold compared to the threshold of NOAA. Through the correction, this study can set a constant threshold every day without determination of different thresholds. In conclusion, this study can achieve the detection applying the single specific threshold regardless of the moon phase.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.58 no.3
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• pp.223-229
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• 2022

This study investigated the methods of effectively removing noises in the acoustic data collected from the cold water zone of the East Sea, and converted that data into NASC values for comparison and analysis. First, the noises accompanying the acoustic data were divided into background noise, impulse noise, transient noise and attenuated signals according to the pattern characteristics. Then, the NASC values before and after noise removal were compared. As a result, the background noises were found to show the highest difference of 6,946 times in the NASC values before and after removal. The attenuated signals showed that the NASC values were higher after the removal.

• Fisheries and Aquatic Sciences
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• v.26 no.4
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• pp.256-267
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• 2023

The suitability of any fish species for successful aquaculture requires basic information on its reproduction and growth. This study investigated some facets of the reproductive biology of Synodontis shall (Mochokidae) from River Siluko in Nigeria. Fish samples were collected forth-nightly for a duration of fourteen (14) months-March 2015 to April, 2016 with the assistance of artisanal fishermen. Fishes were identified using taxonomic guides and standard techniques were used for determination of sex ratio, gonad maturation and fecundity. Linear regression method was used to define the correlation between fecundity and fish length, body weight and ovary weight. Results showed that sex ratio did not indicate a significant divergence (p > 0.05) from the 1 male to 1 female distribution ratio (1:1.41). Gonad morphology revealed paired gonads. Testes and ovaries were classified into four maturity stages: immature, resting, ripening and ripe. Gonadosomatic index ranged from 0.04 to 5.68 (males) and 0.03 to 20.19 (females). Absolute fecundity ranged from 1,014 to 4,520 eggs (mean = 2,592 eggs) and did not correlate significantly (p > 0.05) to ovary weight. This study has contributed to existing data on the biology of freshwater fish species in Nigeria and provided valuable information for fishery management tools in the conservation and utilization of this valuable freshwater fish species.

• Journal of Animal Reproduction and Biotechnology
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• v.38 no.2
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• pp.54-61
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• 2023

Background: Germ cells undergo towards male or female pathways to produce spermatozoa or oocyte respectively which is essential for sexual reproduction. Mesenchymal stem cells (MSCs) have the potential of trans-differentiation to the multiple cell lineages. Methods: Herein, rat MSCs were isolated from bone marrow and characterized by their morphological features, expression of MSC surface markers, and in vitro differentiation capability. Results: Thereafter, we induced these cells only by retinoic acid supplementation in MSC medium and, could able to show that bone marrow derived MSCs are capable to trans-differentiate into male germ cell-like cells in vitro. We characterized these cells by morphological changes, the expressions of germ cell specific markers by immunophenotyping and molecular biology tools. Further, we quantified these differentiated cells. Conclusions: This study suggests that only Retinoic acid in culture medium could induce bone marrow MSCs to differentiate germ cell-like cells in vitro. This basic method of germ cell generation might be helpful in the prospective applications of this technology.