• 수산해양기술연구
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• 제51권1호
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• pp.42-49
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• 2015

According to the catch condition of Scomberomorus niphonius in autumn season affected greatly, the catch price for the set net fishery. Catch production and the selling price were relatively even except 2009 showing a great big blooming jellyfish of Nemopliema nomurai in 2008~2011. The fishing cost of the set net fishery in Yeosu has increased gradually by the decrease of catch production and unexpected environmental change like as jelly fish blooming. The increase of fishing cost diminished net income and caused a negative impact in profitability. The lowest Fisheries ratio of gross profit to gross costs the set net fishery were appeared 60.2% in 2010, respectively. Bycatch was highest in 2008 and lowest in 2009. In general, the bycatch was occurred from May to July every year and when Scomber japonicus was most dominant in the catch price by bycatch had a advantage in the profit side. However, the catch increase of immature small fishes by the bycatch, which will bring about the decrease of fisheries resources. Finally, the present state in set net fisheries will act as a defect on the long-term management of fisheries resources.

• 수산해양기술연구
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• 제51권1호
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• pp.128-135
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• 2015

The worldwide abundance of various jellyfish appears to have increased in coastal ecosystems in recent years. The enormous jellyfish blooms cause a variety of problems for the local ecology, fisheries, and aquatic-sports in coastal locations. In this study, jellyfish sting protection net was installed to ensure the safety and reduction of the inflow into the Haeundae beach. In order to confirm the stability of the protection net, the tension for protection net was measured from variation of current speed. The periods for maximum tension were observed correspond to the periods of maximum current speed. The maximum tension for protection net was measured up to 4,100 kg. From field evaluations, the jellyfish sting protection net has demonstrated to stability from the current and tide in the Haeundae beach.

• 수산해양기술연구
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• 제48권3호
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• pp.256-268
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• 2012

The Nemopilema nomurai is a large jellyfish attaining a weight of 200 kg and bell diameter of 2 m when fully grown. To prevent damage to this species, this study determined the acoustic characteristics of N. nomurai using frequencies 38 and 120 kHz. The CPUE of N. nomurai and the averaged SV of 38 and 120 kHz had a lower (+) correlation coefficient and relationship at 120 kHz (R=0.51) than at 38 kHz (R=0.15) was significant. In addition, the averaged SV at 120 kHz was higher than at 38 kHz. The ${\Delta}MVBS_{120-38}$ in section catches ${\geq}97.8%$ wet mass of N. nomurai was -2.2 to 5.6 dB. The ${\Delta}TS_{120-38}$ in situ TS was extracted in sections catches of only N. nomurai by FMT. It was found that the averaged in situ ${\Delta}TS_{120-38}$ were at 0.6 and 0.1 dB. Furthermore, it results showed a close relationship between the bell diameter and TS of N. nomurai. The dominance of smaller N. nomurai (11.0~20.0 cm bell diameter in the air) corresponded to a similar proportion of low TS values (-69.0~-65.0 dB). A small number of larger N. nomurai (25.0~38.0 cm bell diameter in the air) were collected, in which TS values were the highest (-62.0~-58.0 dB).

• 수산해양기술연구
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• 제48권3호
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• pp.242-255
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• 2012

The Nemopilema nomurai a very large jellyfish that has been found in the East China Sea and is now are migrating to Korea and Japan. To investigate the occurrence of N. nomurai based on the changing marine environment of the East China Sea, we conducted field survey in the early summer from 2006-2008. We observed the marine environment using CTD and the occurrence of N. nomurai using FMT and bottom trawling. We caught the most N. nomurai in 2007 and the fewest in 2008 and environment factors influencing its are more sensitive temperature than salinity. Large quantities of N. nomurai with a small bell diameter were caught in 2007 and large individuals with a significant bell diameter were caught in 2008. This appeared which between the catch and bell diameter of N. nomurai had (-) correlation (R=-0.988, p=0.098). Meanwhile, the spatial distribution of N. nomurai concentrations in lower salinity mixed seawater inflow in Changjiang Diluted Water.

• Ocean and Polar Research
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• 제32권2호
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• pp.113-122
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• 2010

Understanding the abundance and distribution of massive jellyfish is necessary to forecast where or when their blooms will happen. The acoustic technique is one of the most useful methods of obtaining information if the acoustic characteristics of the targets are known. This study was conducted to determine the acoustic target strength (TS, dB) of two jellyfish species, Aurelia aurita and Cyanea nozakii, in the southern coast of Korea. For the ex situ measurements, 120, 200, and 420 kHz split beam transducers were used, and jellyfish with various bell lengths were arranged to prepare multiple jellyfish. Under 2 vertical individuals, the mean TS for multiple A. aurita at 120, 200, and 420 kHz was -72.7, -71.7, and -68.2 dB, respectively. In the case of 5 vertical individuals, the mean TS of the species was -71.3, -68.2, and -62.0 dB. Finally, the mean TS of C. nozakii at 120, 200, and 200 kHz was -62.0, -60.3, and -58.2 dB under 2 individuals and -58.1, -57.4, and -54.0 dB under 4 individuals, respectively. For both species, higher numbers of jellyfish resulted in a higher TS. In addition, higher frequencies were associated with a higher TS for the same jellyfish. These TS results for two species can be used as essential data for the acoustic detection of jellyfish in an open ocean or coastal area.

• 한국수산과학회지
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• 제47권5호
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• pp.482-488
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• 2014

The study investigated the chemical composition, pH, and texture of salted jellyfish processed in Indonesia, Thailand, and China as a pilot study for processing the jellyfish Nemopilema nomurai, which occurs in Korean coastal waters. The 14 samples of salted jellyfish included processed umbrella and oral arms and consisted of 68.4-78.3 g/100 g moisture, 1.79-4.37 g/100 g crude protein, and 0.07-0.41 g/100 g crude lipid. The total amino acid content was 2.30-4.69 g/100 g and glycine accounted for 20.07-37.37% of the total amino acids. Salting jellyfish reduces the possibility of microbial growth and enhances the shelf life because the samples have a pH of 3.77-4.35, salinity of 18.53-24.02%, and lower water activity of 0.77-0.80. The lightness (L), redness (a), and yellowness (b) of the samples were 53.98-61.32, 1.76-6.26, and 14.08-29.0, respectively. The springiness, strength, and hardness of the salted jellyfish differed significantly among the products. The sample processed in Indonesia had the highest springiness. While the chemical composition, pH, water activity, and color differed significantly among the products, there were no significant effects of the country of manufacture. These results will enable the determination of quality index parameters for salted processed Nemopilema nomurai caught in Korean coastal.

• 한국수산과학회지
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• 제47권5호
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• pp.459-473
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• 2014

The recent mass appearances of jellyfish in Korea have caused economic and social damage, as they plague swimmers and fishermen. However, jellyfish have high economic and nutritional value, and contain low levels of calories and hydrolysates. Thus, jellyfish are a natural, healthy food that can improve high blood pressure, bronchitis, and a multitude of other diseases. Here, we present research on the ecology, classification, bloom, damage caused, food component characterization, and tissues of jellyfish, with the aim of facilitating further study. Research on use of jellyfish as salted products, and for collagen and qniumucin would also be valuable. A jellyfish body is classified into three parts: the body, termed the umbrella; the oral arm; and the tentacle. Jellyfish are planktonic marine members of a group of invertebrate animals comprising the classes Schypozoa (phylum Cnidaria) and Cuboza. In Korea in 2012, jellyfish damage resulted in decreases of annual catch and commercial value estimated at 177 and 141 billion won, respectively. Because concentrations of heavy metals are below the safety limits for seafood, dried jellyfish appear to be safe raw materials for food. The proximate compositions of Nemopilema nomurai and Aurelia aurita were 97.1% and 96.5% moisture, 0.9% and 1.2% crude proteins, undetected and 0.1% crude lipids, and 1.7% and 1.8% ash, respectively. According to their total contents of essential, total, and non-essential amino acids, jellyfish gonads were deemed good-quality protein. Because the major functional components of jellyfish are collagen and qniumucin, jellyfish can be used salted, or these components of healthy diets can be extracted from them. For more effective use of jellyfish, unit costs should be decreased and safety guaranteed. Additionally, dehydrators attached to conveyor belts should be developed. Since jellyfish can be used throughout the year, they should be listed in the Korean Food Standards Codex as a food source.

• 수산해양기술연구
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• 제51권3호
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• pp.295-301
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• 2015

Target strength (TS) information is an important parameter that estimates the detection, distribution, and abundance of Aurelia aurita. In order to investigate the biological TS of jellyfish, some factors such as size (bell diameter), tilt angle, pulsation, and symbion should be known. In the ex situ TS measurements, the tilt angles and pulsation from synchronized swimming behavior of four live A. aurita (bell diameters in the air: 54.2 ~ 94.2 mm) were measured with the acoustic data at 70 kHz. The reduced target strength (RTS) of A. aurita was found to change ranged from 13.4 ~ 16.5 dB according to the incidence angles from $-30^{\circ}$ to $24^{\circ}$. When the change rate of bell diameter in the water was 0.2, the TS value showed a 7.2 dB change. These results could be utilized as an important data to understand the acoustic characteristic scattering of A. aurita.

• 한국수산과학회지
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• 제44권5호
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• pp.478-483
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• 2011

An antimicrobial material was purified from the acidified whole body extract of the jellyfish Nemopilema nomurai by using C18 reversed phase and cation-exchange high performance liquid chromatography (HPLC). Whole body extract and the purified compound (JAP-1) showed potent antimicrobial activities against a wide range of microorganisms including Escherichia coli D31, Bacillus subtilis, Streptococcus iniae and Candida albicans, without significant hemolytic activity. Treatment of JAP-1 with trypsin completely abolished all antibacterial activity against Bacillus subtilis, suggesting that JAP-1 is likely to be a proteinaceous antibiotic. The molecular weight of JAP-1 was determined to be 680.10 Da by MALDI-TOF mass spectroscopy.

• 한국수산과학회지
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• 제52권6호
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• pp.725-734
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• 2019

Moon jellyfish Aurelia coerulea are highly abundant off the coast of Tongyeong, Korea. We measured the density of A. coerulea in this area using a scientific echosounder at frequencies of 38 and 120 kHz, and then applied a distorted wave Born approximation (DWBA) model to calculate the target strength of the echosounder at each frequency. Then, we used the frequency difference method to extract jellyfish echo signals and estimate the A. coerulea density. A. coerulea was evenly distributed throughout the water column; the backscattering strength ranged from -75 to -65 dB. In May and August, the A. coerulea densities at survey lines 3 and 4 were estimated at 1.5-1.6 and 0.2-0.9 g/m2, with mean weighted densities of 1.04 and 0.48 g/m2, respectively. In September, the A. coerulea densities estimates in Jaran Bay and Goseong Bay were 0.6-2.1 and 0.1-0.4 g/m2, with mean weighted densities of 1.25 and 0.24 g/m2, respectively.