• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.49 no.3
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• pp.250-260
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• 2013

The annual and monthly fluctuation in the species composition and the catch abundance of dominant species were analyzed using the daily sales slip catch data by a set net in the offshore waters off Dolsan Island in Yeosu from March 2004 to December 2011. Mean catch from 2004 to 2011 is 372M/T and the maximum and the minimum catch are 526 M/T in 2005 and 27 2M/T in 2009, respectively. The dominant species were Engraulis japonicus mainly in spring and Scomberomorous niphonius in Autumn and therefore the set net catch that is dominated by S. niphonius's catch was much higher in autumn than in spring. Through comparative analyses for the environmental factors to the annual catch fluctuation, it is revealed that the water temperature variation affected the recruitment property of S. niphonius to the fishing ground but the effect of typhoon on the catch fluctuation was not distinct. Furthermore, the big blooming event of jellyfish, particularly Nemopilema nomurai, that occurred in 2009 showed a tendency of faster appearance and later extinction until December. The occurring characteristic of N. nomurai became a direct cause that brought about the lowest total catch in 2009 since the dominant species catch of the set net fishery was concentrated mostly in Autumn.

• Fisheries and Aquatic Sciences
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• v.4 no.3
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• pp.120-129
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• 2001

Thirty-six dinoflagellate cysts, representing 15 genera were identified in the surface sediments obtained from the northwestern East China Sea. Three cyst morphotypes found in this survey have not previously been described in the East China Sea and adjacent waters: Seleno­pemphix sp. 2, Selenopemphix sp. 3 and Trinovantedinium sp. 1. In the northwestern East China Sea, Operculodinium centrocarpum, Spiniferites bulloideus and ellipsoidal cysts of Alexandrium were commonly observed. Moreover, it was recognized that the ellipsoidal cysts of Alexandrium, whose motile cells of A tamarense and/or A catenella are responsible to paralytic shellfish poisoning, distributed not only restricted to the coastal areas but also to the offshore stations far from the Changjiang River mouth.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.50 no.4
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• pp.429-436
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• 2017

The seasonal and interannual variations in fish assemblages in the coastal waters off Gijang were examined with an otter trawl from 2015 to 2016. A total of 59 fish species was collected during the study period. The dominant species were Caelorinchus multispinulosus, Clupea pallasii pallasii and Chelidonichthys spinosus. Seasonal changes in fish assemblages appeared to be distinct in the study area. The fish assemblages in summer and autumn were clearly distinguishable from those in other seasons, and the largest numbers of species and individuals were captured in winter and summer, respectively. Because fish assemblages are closely related to changes in water temperature, long-term changes in water temperature can have a significant impact on the productivity of offshore fisheries by changing fish species composition, habitat migration, and growth rate of fish.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2001.10a
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• pp.315-316
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• 2001

Fourteen species of the family Penaeidae have been previously reported from the Korean waters (Kim, 1977: Cha et al., 2001). Recent collections from the coastal waters of Korea revealed the presence of two penaeid species, Metapenaeopsis lata Kubo, 1949 and Parapenaeopsis cultrirostris Alcock, 1906. These two species have been reported from Japan, East China Sea and Sou China Sea, and the Indo-West Pacific low South China Sea. We present brief notes of these species as two new members of the Korean fauna. (omitted)

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.34 no.2
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• pp.139-143
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• 1998

In the fishing process on the sea eel pots, the most dangerous and difficult labor is manually separating process of several thousand pots from main line with high speed hauling operation. In this study, the automatic separating system of the pot from main line is developed. This system is composed with the clip connected to the pot by branch line, the keeper attached to the main line by pressing and the separator separating the clip and the keeper. In the experiment, static and dynamic characteristics of the system are investigated. From the considerations on the experimental results, it is ascertained that the automatic separating system of the pot from main line proposed in this study has good operating performance.

• Fisheries and Aquatic Sciences
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• v.12 no.2
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• pp.152-161
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• 2009

The largehead hairtail (Trichiurus lepturus) is one of the most common fisheries stocks in the East China Sea and the Yellow Sea. The species is caught using a variety of fishing tools, such as a stow net or a long line, as well as jigging and trawling. Scientific investigations have been conducted throughout the world to enable evidence-based estimations for the management and protection of the main fisheries biomass. For example, inshore and offshore hydro acoustic surveys are performed annually using bottom- and mid-water trawls around the Korean Peninsula. However, to date, no acoustic survey has been conducted to estimate fish size distribution, which is necessary to construct a data bank of target strength (TS) relative to fish species, length (L), and frequency. This study describes the frequency and length dependence of TS among fishes in Korean waters for the purpose of constructing such a TS data bank. TS measurements of the largehead hairtail were carried out in a water tank (L 5 m$\times$width 6 m$\times$ height 5 m) at frequencies of 50, 75, 120, and 200 kHz, using a tethering method. The average TS patterns were measured as a function of tilt angle, ranging from $-45^{\circ}$ (head down) to $+45^{\circ}$ (head up) every $0.2^{\circ}$. The length conversion constant ($b_{20}$) was estimated under the assumption that TS is proportional to the square of the length. In addition, in situ TS measurements on live largehead hairtails were performed using a split beam echo sounder.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.51 no.4
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• pp.553-560
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• 2015

The feeding habits of the Pacific bluefin tuna, Thunnus orientalis were examined based on the stomach contents of 330 specimens caught by offshore large purse seine fishery in the southern sea of Korea, 2011. The size of Pacific bluefin tuna used in this study ranged from 34.1 to 67.3 cm in fork length (FL). The percentage of empty stomachs was 41.8%. The main prey items were Pisces and Cephalopoda based on percentage IRI (index of relative importance). The main fish preys were Trachurus japonicus, Bregmaceros japonicus, Engraulis japonicus, and Cephalopoda were Todarodes pacificus, Loligo edulis, Watasenia scintillans. T. orientalis showed ontogenetic change in diet composition. Although Pisces dominated the diet of all length classes the portion of Cephalopoda was relatively higher in size between 40 and 50 cm other than length classes. In terms of seasonal variation in feeding habits, Pisces was the main prey group in all seasons, but Cephalopoda was also frequently consumed during spring and autumn based on %IRI.

• Journal of the korean society of oceanography
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• v.37 no.4
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• pp.212-223
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• 2002

Cochlodinium polykrikoides bloom in 1995 was studied with a focus on an unusual coastal environment in the South Sea of Korea. Data on temperature, salinity, and zooplankton biomass during 1965-1998 and nutrients during 1990-1998 and chlorophyll-a during 1995-1998 were used in this study. These data were obtained from the serial oceanographic observations in Korean waters carried out by the National Fisheries Research and Development Institute. In 1995 the C. polykrikoides bloom began in the coastal area around Narodo Island in August and consequently occurred to the whole coastal area of the South and East Seas of Korea. During June-October 1995, the coastal environment was unusual compared with the long-term means during 1965-1998. In June 1995, sea surface temperature was 1-2$^{\circ}C$ warmer than in other years in all coastal areas, while salinity was high only to the east of Jeju Island. In August 1995, a strong coastal front appeared inshore of a line between Jeju and Tsushima Islands. In particular, a strong coastal front which showed the characteristics of upwelling front occurred in the coastal area around Narodo and Sorido Islands, not only because of a strong intrusion of the Tsushima Warm Current but also because of the upwelling of cold bottom water. Salinity was low in the neighboring waters of western side of Jeju Island. Nutrients and chlorophyll-a were high in the inshore area between Narodo and Sorido Islands in 1995 in contrast with the other years and areas. Zooplankton showed an unusually high abundance in the coastal area in October 1995. We conclude that the Tsushima Warm Current strongly influenced the South Sea of Korea in 1995 and created strong upwelling front bordering cold upwelled water in the coastal area around Narodo and Sorido Islands. It leads us that these physical structures introduce the favorable environment for the development of C. polykrikoides blooms. We suggest that C. polykrikoides has a bio-physical tolerance of high shear and stress and prefers frontal and upwelling relaxed areas as its habitat. We also find that nutrients were not supplied to the coastal area from the offshore where a low salinity water mass with high nutrients appeared around Jeju Island. Because the strong upwelling front protect the reach of offshore low saline water mass. The main source of nutrients was the upwelled water mass in the coastal area of Wando-Narodo-Sorido.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.24 no.4
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• pp.266-271
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• 1991

Probably herbivorous fishes were visibility main body as aquatic substantial production in offshore and adjacent sea. It is a major problem to estimation of energy conversion rate by hervivores from primary production when to be measurement for potential productivity of herbivores as above meaning according to deductive method. This was deal with review of I index, with mean transfer efficiency from food in seawater to food in gut be eaten by a particular species. Yet $K_i$ was not settled with an established theory. In this review coefficients of food selection or electivity indices suggested by two Russian biologists, Ivlev and Sorygin, (r-p) /(r+p) and (r/p) were understand unsuitable to use with the transfer efficiency $K_i$. But CCOS that is one of community resemblance chord is suggested to be possible with someone a treatment, as (CCOS)$\times$(Filtering rate).

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2022.10a
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• pp.229-232
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• 2022

Recently, production of offshore fisheries in Korea has been decreasing. Since production of offshore fisheries in 2016 fell below 1 million tons for the first time in 44 years, it has not recovered and has been decreasing. In order to cope with such a decrease in fishery resources, the TAC (total allowable catch) system is implemented internationally for fisheries resource management. Since 1999, South Korea has introduced the TAC system to perform resource management. In this paper, we propose an artificial intelligence-based fish classification and weight estimation system that can be used to investigate fishery resources of land observers essential for the implementation of the TAC system. The system consists of an app and a cloud server that automatically measures the body size and height of fish and takes photos using a terminal equipped with a lidar sensor. In the cloud server, fish classification is performed using a CNN-based efficientnet model and the weight of fish is predicted using automatically measured body length and body height information. Using this system, it is possible to improve the existing method in which the land observer manually writes after measuring the tape measure and weight in the stomach market.