• 한국수산과학회지
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• 제22권2호
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• pp.86-94
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• 1989

Yellowfin and bigeye tunas have been targeting and the most important species for the Korean tuna longline fishery in the Indian Ocean. This study is aimed to analyse the fishing efficiency of the regular and the deep longlines and the vortical distribution of tunas, and the weight composition by fishing depth based on the data from Korean tuna longline fishery from 1973 to 1980 and from 1984 to 1986 in the Indian Ocean. It was found that the deep longline gear on bigeye tuna was significantly different from the regular longline gear on yellowfin tuna in the whole Indian Ocean. Yellowfin tuna and billfishes were chiefly distributed at the shallow layer and bigeye at the deep layer. The weight composition of yellowfin and bigeye tunas by depth showed that the deeper the depth, the larger the bigeye distributed.

• 한국수산과학회지
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• 제38권3호
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• pp.196-204
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• 2005

The horizontal and vertical distribution of yellowfin tuna, Thunnus albacares (Bonnaterre) and bigeye tuna, Tunnus obesus (Lowe) in relation to oceanic conditions such as thermal structure produced during El Nino/La Nina episodes were analyzed on the basis of data sets for the catches and efforts from the Korean tuna longline fishery and for the oceanographic observations from the NOAA during 1982-2002 in the tropical Pacific. The high density of fishing ground appeared in the western Pacific ($5^{\circ}N-5^{\circ}S,\;160^{\circ}E-180^{\circ}W$) for yellowfin tuna and in the eastern Pacific ($5^{\circ}N-15^{\circ}S,\;130^{\circ}W-100^{\circ}W$) for bigeye tuna. yellowfin and bigeye tunas were mainly distributed at the 110-250 m layer and 245-312 m layer, respectively, in the western Pacific. However, in the eastern Pacific, they were mostly caught at the 116-161 m and 205-276 m layer for yellowfin tuna and bigeye tuna, respectively. It can be suggested that bigeye tuna be distributed in the deepest layer among tunas and show a vertical size stratification. It was observed that during the El Nino events the main fishing ground of yellowfin tuna shifted from the western Pacific toward the eastern Pacific. In the eastern Pacific which showed a higher density of bigeye tuna, the vulnerability of bigeye tuna caught by deep longline increased during the El Nino events due to deepening of thermocline layer and a more intensively distribution of the fish schools in the lower layer of thermocline during the El Nino events.

• 수산해양기술연구
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• 제41권3호
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• pp.188-198
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• 2005

This study was conducted to survey the catches of vertical bottom longline fisheries in the sea mount of central northern Pacific($30^{\circ}-42^{\circ}N$, $170^{\circ}-175^{\circ}E$), during the period of July 1 to August 25,2004 by commercial fishing vessel. The number of 57 test fishing was carried out in the central northern Pacific during 43 days and the total catches were 21,092.4kg as 19 fish species, CPUE/day and catches/day were 185 baskets and 490.5kg, respectively. Main fish species caught from the experimental fishing were Squalus mitsukurii (66.3%), Coelorhyrchus asperocephaius (11.7%) and Helicolenus avius (9.8%) and, average inside diameter for fish mouth was 4.0cm over. Catch ratio according to each fishing ground was the order of F, D, J, B and C. Catch ratio fur water depth was the order of 450-500m, 350-400m, 300-350m, 400-450m, 1000-1100m and 500-550m and, main species by water depth was Squalus mitsukurii for 300-400m, Etmopterus lucifer for 300-550m, Coelorhyrchus asperocephaius far 1,000m over. Catch ratio according to the kind of hooks was higher at the hook no.6 for Squalus mitsukurii and no. 5 for Etmopterus lucifer and, catch ratio by baits was higher at squid for Squalus mitsukurii, saury and eel for Helicolemus avius and saury for Etmopterus lucifer. Accordingly, it is thought that the extension of fishing hours is needed with the reduction of damage and loss for fishing gears during fishing operation.

• 한국수산과학회지
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• 제28권1호
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• pp.35-48
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• 1995

To develop the optimal design method for the longline type scallop culturing facilities in the open sea numerical calculations and hydraulic model experiments are carried out for the stability and function optimization. Using the results for the motion and tension of the facilities, stable design concepts and effects of motion control system by vertical anchor and resistance discs art discussed. The results of this study that can be applied to the design are as follows: 1) Total external forces by design wave $(H_{1/3}\;=\;6,7\;m,\;T_{1/3}\;=\;12sec)$ at the coastal waters of Jumunjin for unit facility (one main line) are estimated to 5-20 tons, and required anchor weights are 10-40 tons in the case of 2-point mooring system. Though the present facilities are stable to steady currents, but is unstable to the extreme wave condition of return period of 10 years. 2) The dimensions and depth of array systems must be designed considering the ecological environments as well as the physical characteristics including the mooring and holding forces that are proportional to the length and relative depth of main line to wave length, and the number of buoys and nets. 3) Oscillation of the facility is influenced by water particle motion and the weight of hanging net, and is excited at both edge, especially at the lee side. To reduce the motion of the nets, the vertical anchoring system and the resistence disc method are recommended by the experimental results, 4) The damage of rope near the anchor by abrasion should be prevented using the ring-type connection parts or anchor chains.

• 수산해양기술연구
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• 제53권2호
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• pp.126-131
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• 2017

To improve the efficiency of hairtail trolling, it is important to gain an accurate understanding of the distribution of fish based on their diurnal vertical migration patterns. This study evaluated the vertical distribution of hairtails through catch efficiency tests using vertical longlines. Five replicate tests of the efficiency were carried out on the eastern coast of Jeju Island from August to September 2016, from 11:00 AM to 03:00 PM in the daytime and 11:00 PM to 03:00 AM in the nighttime. The fishing gear was composed of 20 hooks per line set, numbered in order from the first hook near the surface to the last hook on the seabed. The depth of the first hook was 18 m, and that of the last hook was 86 m. Pacific saury was used as the baits. In total, 10 sets of fishing gear were used per trip. After fishing, we counted the hairtails at each numbered hook, which were summed up both by number and in aggregate. A total of 232 hairtails were caught using 2,000 hooks: 193 individuals at daytime and 39 at nighttime. The hook rate was 11.5% : 9.6% at daytime; 2.0% at nighttime. For both daytime and nighttime catches, there were variations in the hook rates at each numbered hook. In the daytime, a maximum of 28.5% catches occurred at hook number 18, followed by 21.4% at number 20, and 10.7% at number 17, accounting for 60.6% of the daytime hook rates. In the nighttime, a maximum of 23.0% catches occurred at hook number 1, followed by 15.3% at hook number 4 and 9, accounting for 53.6% of the nighttime hook rate. Based on the above results, hairtails are usually distributed in deeper region in daytime, whereas they occur near the surface in nighttime. Therefore, it is necessary to position trolling lines according to diurnal vertical distribution layers of hairtails for fishing efficiency.

• 한국어류학회지
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• 제35권3호
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• pp.201-206
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• 2023

2017년 11월 1일 제주도 주변 해역에서 주낙으로 하스돔과 (Haemulidae)에 속하는 Plectorhinchus vittatus 1개체가 처음 채집되었다. 본 종은 체측에 8개의 검은색 세로줄 무늬가 있고, 등지느러미, 뒷지느러미, 꼬리지느러미에 검은 물방울 무늬가 산재하는 점에서 P. vittatus로 동정되었다. 형태적으로 매우 유사한 Plectorhinchus lineatus와는 새파 수(28 in P. vittatus vs. 20~22 in P. lineatus), 복부의 줄무늬(있음 vs. 없음), 배지느러미 기부의 검은 무늬(없음 vs. 있음)에서 명확히 구분된다. 본 종은 남위 27°에서 북위 31° 사이에 분포하는 것으로 알려졌으나, 본 연구에서 북위 33°에서 채집되어 북방한계수역의 확장을 시사한다. 국내에서 처음 채집된 본 종의 국명은 Lee et al. (1999)에 의거 "추사어름돔"을 제안한다.