• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.38 no.2
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• pp.156-163
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• 2002

In order to development the construction and dimension of fishing gear for gizzard shad coastal purse seine, first of all investigated to the sinking speed and underwater geometry of net, behaviour of fish school to the net during the fishing operation In the field. The results obtained are summarized as follows; 1. Average sinking speed of net was 13cm/sec in bunt, 9.0cm/sec and 9.5cm/sec in 170m and 280m of center, 4.9cm/sec in end wing side, therefore was fastest in start of shooting and decreased gradually during the shooting process. 2. The most of leadline was reached in bottom from the shooting immediately to hauling time and the mean depth of timber bar used equipment for the escaping prevention of fish school was within the 2.7m. 3. The fish school of gizzard shad was appearanced higher density and remained to the most time in bottom than the surface and repeated to vortical movement, and its tendency to distinct in rapid time of tide current. 4. Behaviour of fish school in the net was showed to the vortical movement by sinking and rising immediately with the shooting of net and then divide with the two shape to follow round the wall of net and no patterns straightly movement in the net, and tendency easily catched in fish school of the wall of net. 5. Escaping of fish school in the gap of wing side was to busy after that seting the timber bar, therefore its function for escaping prevention of fish school was very lowed. 6. Escaping behaviour of fish school was differenced with the depth of fishing ground, the above 20m escaped to busy through the below in ledline because the sinking speed of fish school is fast than the net.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.14 no.4
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• pp.239-252
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• 1981

The East China Sea is an important region as nursery and spawning grounds for pelagic fishes such as jack mackerel, common mackerel etc. , and thus constitutes a major fishing area for purse-seine fishery. The environment surrounding in this region is under the influence of the Yellow Sea Cold Water, China Coastal Water and Kuroshio Current. The purpose of this study was to clarify the effects of oceanographic conditions and thermal fronts on the formation of the fishing grounds for the mackerels in the East China Sea. Through the analyses of fisheries statistics during 1968-1976 and temperature data, the following facts are found: 1) Approximately $70\%$ of the total mackerel(common) catches appeared to be come from the Tsushima Current region which includes Sakai coast of the Japan Sea, eastern Tsushima and Shirase Island, and Jeju Island of Korea. This area covers only about $8\%$ of the East China Sea. 2) Main fishing grounds for the jack mackerel are also centered around the area of southwestern Goto, Shirase and eastern Tsushima Island where the catches accounted for about $54\%$ of the total jack mackerel catches. 3) Fluctuations in annual catches are relatively small in the Tsushima Current region, compared to other regions such as Yellow Sea, southwestern coast of Kyushu and mid-western part of the East China Sea, where the fisheries yields varied considerably due to unstable fishing conditions. 4) It appears that the fishing grounds for the jack mackerel are mainly distributed along the warmer region ($15-20^{\circ}C$) of the thermal front, and those for the common mackerel are in somewhat colder region ($13-16^{\circ}C$) in the Tsushima Current.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.48 no.3
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• pp.377-385
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• 2015

The age and growth of the skipjack tuna Katsuwonus pelamis were determined using otoliths sampled from a Korean tuna purse seine fishery in the Western and Central Pacific Ocean from January 2005 to September 2006. A total of 312 otoliths were used to estimate the ages of skipjack tuna, which ranged from 1 to 7 years. The relationships between otolith ring radius (R) and fork length (FL) for female, male, and sex combined were FL = 19.74R + 1.50 ($r^2=0.54$), FL = 17.66R + 6.35 ($r^2=0.47$), and FL = 18.83R + 3.36 ($r^2=0.53$), respectively. The back-calculated fork lengths of each age ($FL_{year}$) were $FL_1=36.2cm$, $FL_2=43.3cm$, $FL_3=48.3cm$, $FL_4=52.6cm$, $FL_5=56.5cm$, $FL_6=60.8cm$, and $FL_7=63.2cm$. The relationships between fork length (FL) and total weight (TW) for female, male, and sex combined were $TW=0.00001FL^{3.19}(r^2=0.95)$, $TW=0.00001FL^{3.17}(r^2=0.95)$, and $TW=0.000009FL^{3.23}(r^2=0.95)$, respectively. The von Bertalanffy growth parameters of skipjack tuna estimated in this study were $L_{\infty}=77.4cm$, K = 0.176/year, and $t_0=-2.569years$.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.52 no.3
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• pp.209-219
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• 2016

The survey was conducted to investigate biomass and distribution of fisheries resources using a quantitative echo sounder and a fixed gillnet around Marado coast of Jeju to obtain the scientific basic data for dispute resolution with a large purse seine fishery and coastal fishing and policy establishment of reasonable fisheries resources. Hydroacoustic surveys were conducted six times (November 28~29, 2015 (night), February 23~24, 2016 (night) and March 3~4, 2016 (night/day), March 30~31, 2016 (night/day)) using a quantitative echo sounder. The pelagic fish densities were relatively higher around Marado in November 2015, February 2016 and March 3~4, 2016. However, demersal fish densities were relatively higher in Jeju coastal waters on March 30~31, 2016. Catch data using fixed gill net were used to calculate biomass. Based on the hydroacoustic data, fish length-weight function and target strength information of dominant fish, the biomass of fishes were estimated as follow: 5.64 ton CV = 70.2% at night on November 28-29 2015, 7.14 ton CV = 35.8% of pelagic fish and 530.77 ton CV = 34.6% of demersal fishes at night on February 23-24 2016, 2.34 ton CV = 56.7% of pelagic fish and 571.93 ton CV = 40.3% of demersal fish at daytime, 1.39 ton CV = 48.4% of pelagic fish and 194.59 ton CV = 54.3% of demersal fish at night on March 3~4 2016, 0.37 ton CV = 72.9% of pelagic fish and 338.79 ton CV = 99.7% of demersal fish at daytime, 0.24 ton CV = 21.3% of pelagic fish and 68.61 ton CV = 53.8% of demersal fish at night on March 30~31 2016.