• 수산해양기술연구
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• 제53권3호
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• pp.219-227
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• 2017

In pelagic longline, deploying the gear such that the depth of the hook is the same as that of the target fish is important to improve the fishing performance and selectivity. In this study, the depth of the tuna longline hook was estimated using the mass-spring model, catenary curve method, and secretariat of the pacific commission Pythagorean method in order to improve the performance of the longline gear in Fiji. The former two methods were estimated to be relatively accurate, and the latter showed a large error. Further, the mass-spring model accounted for the influence of tidal current in the ocean, which was found to be appropriate for use in field trials.

• 수산해양기술연구
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• 제45권1호
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• pp.22-33
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• 2009

Ecological risk assessment(ERA), developed in Australia, can be used to estimate the risk of target, bycatch and protected species from the effects of fishing using limited data for stock assessment. In this study, we employed the ERA approach to estimate risks to tunas, billfishes, sharks, sea turtles and other species by the Korean tuna longline fishery in the Western and Central Pacific Ocean using productivity and susceptibility analyses of the ERA based on low(<1.30), medium(1.30-1.84) and high risk(>1.84). Albacore, bigeye, yellowfin, skipjack and bluefin tunas were generally evaluated in the medium risk. The susceptibility of tuna species, however, had higher risks than the productivity. Billfishes were also at medium risk, while sharks were at high risk by the tuna longline fishery. The risk of productivity was generally high, because most sharks caught by the tuna longline fishery have high longevities, i.e., over 10 years, including ovoviviparous species. Susceptibility, which is related with the selection of fishing gear, was also high, because the longline fishery has no gear modifications to prevent bycatch of protected species. Not only target tuna species were influenced by the tuna longline fishery in the Western and Central Pacific Ocean, but also nontarget species, such as pomfret, mackerels rays, sea turtle were done. Ecosystem-based fishery assessment tools, such as productivity and susceptibility analysis(PSA), have the ability to provide broad scientific advice to the policy makers and stakeholders.

• 수산경영론집
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• 제51권3호
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• pp.17-31
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• 2020

The purpose of this study is to identify economic situation on scale of tuna distant longline fishery by analyzing its economies of scale using the cost function. To analyze its economics of scale, the deep-sea fishing statistics were used from 2012 to 2016. In detail, the number of panels for estimating the cost function was 68 tuna distant longline vessels from 2012 to 2016, and the total number of observations over the five years were 340. As a final model, the two-way fixed effect model based on the translog cost function was adopted through the F test, the Breusch-Pagan test and the Hausman test. As a result of the analysis, it was found that tuna distant longline fishery between 2012 and 2014 was diseconomies of scale, the fishery between 2015 and 2016 was economies of scale. However, the economic indicators of the scale from 2012 to 2016 were almost close to zero, indicating that the constant returns to scale, the optimal scale, were reached. Therefore, in the situation where the amount of fishery resources in the world continues to decrease, it is necessary to prepare a method to obtain economic benefits through scale maintenance and reduction rather than indiscriminate scale expansion.

• 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.

• 해양정책연구
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• 제34권2호
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• pp.1-28
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• 2019

The purpose of this study is to analyze the substitution among production factors of Korean distant water longline fisheries in IATTC waters. In the analysis, the translog function which have one output variable of total cost and input variables of labor, fuel, fishing gear, and capital was established and it was transformed into simultaneous equations by each cost. Then, variables of equations were estimated by SUR (seemingly unrelated regression) model. Since distant water longline fisheries is a fishing type with high fuel usage, substitution of fuel with other factors was mainly analyzed. Results showed a substitute relation between fuel and labor as well as fuel and fishing gear, while a complementary relation between fuel and capital. In addition, it was analyzed that magnitude of fuel elasticity with other factors would be inelastic.

• 한국수산과학회지
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• 제54권1호
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• pp.129-134
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• 2021

This study used the commercial fishing data of Korean high sea bottom longline vessels in the South West Atlantic Ocean from 2013 to 2019 to identify the distribution of fishing grounds of Korean longline vessels. We estimated the CPUE of the Patagonian toothfish Dissostichus eleginoides and the changes in its stock status. The fishing grounds of Korean longline vessels were observed to concentrate on the exclusive economic zone (EEZ) boundary between Argentina, Uruguay, and Falkland owing to the high seas of 41-55 °S in the south and 49-60 °W in the west. A high intensity of fishing was seen in the middle area, which was horizontal from the 3.1 subarea. In all the three subareas, CPUEs have had the tendency to decline since 2013. Although the CPUEs in the 3.2.1-2 subareas were the highest in each subarea, there was no significant difference in each subarea (P>0.05). It is believed that the establishment of a regional fisheries organization or the strengthening of the management of FAO is necessary for the management of Southwest Atlantic fisheries and sustainable fishing, because the portion and scope of Korean longline vessels are very low in the Southwest Atlantic; however, the CPUE is estimated to have declined.

• Fisheries and Aquatic Sciences
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• 제25권12호
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• pp.589-600
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• 2022

Longline fishery targeting tunas and tuna-like species is known to produce a significant amount of catch not only for the target species, but also for ecologically related species like sharks, marine turtles, sea birds and marine mammals. Recognizing this seriousness, tuna related regional fisheries management organizations (t-RFMOs) have established conservation and management measures (CMMs) to reduce bycatch and/or interaction with ecosystem vulnerable species including sea turtles and are obliged to implement bycatch mitigation measures and guidelines on safe release to their member countries. Along with development and strengthening of those measures, various case studies have been conducting to verify the effectiveness of bycatch mitigation for ecologically related species. This study examines the background and progress on developing CMMs of t-RFMOs and regulation programs of the United States related to sea turtles, which have recently become one of the main issues, and reviews case studies on sea turtle bycatch mitigation measures to find out the effectiveness of reducing bycatch rate and impacts to the fisheries. In order to respond the consultation process on certification determination with the United States, it was confirmed the current status of implementation on related measures conducted by Korean tuna longline fishery based on scientific observer data and survey for captains. Even though all Korean tuna longline fleets belong to the deep-set longline fishery (100-300m), which is not subject to the obligation of those mitigation measures, they are voluntarily implementing both measures, use of circle hook and whole finfish bait, regardless of which RFMO's Convention area they operate. And the national regulatory and management programs for sea turtle bycatch prevention adopted by Republic of Korea seems to be comparable in effectiveness to that of the United Stated. However, Korea needs to take preemptive measures in establishing sustainable fisheries, including the protection of the marine ecosystem and environment, as stronger requests are anticipated to be made by the international community on this matter.

• 한국수산과학회지
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• 제51권3호
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• pp.286-297
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• 2018

We analyzed scientific observer data to identify species composition and catch trends of Korean tuna longline fisheries in the Indian Ocean. The data were collected by Korean scientific observers onboard Korean tuna longline fishing vessels in the Indian Ocean from 2010 to 2015. The observers identified 94 species including 5 tuna, 6 billfish, 11 shark, 7 other fish, 5 seabird and 1 sea turtle. Albacore tuna Thunnus alalunga and southern bluefin tuna Thunnus maccoyii were the dominant tuna species, and swordfish Xiphias gladius were the most commonly captured billfish. During the survey periods, 87 seabirds were incidentally bycaught. Black-browed albatross Diomedea melanophris was the dominant seabird species in bycatch, especially in 2010. Cluster analysis showed difference in the species composition of catches between the eastern and western Indian Ocean.

• 수산해양기술연구
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• 제47권1호
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• pp.18-26
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• 2011

This study is to contribute to income growth of fishermen by the common octopus fishery characterized in the Tando Bay on the southwest coast of Korea. This area is engaged in Longline fishing (301 persons), Shovel fishing (196 persons), Trap fishing (14 persons) and Torch light fishing (40 persons) in 2008. Population who is joined in the spring becomes main fishery target population of longline fishery in the fall because entering fishing ground in August, and is joined in the fall becomes main fishery target population of longline fishery in the spring because entering fishing ground in December. Average size of common octopus examined by longline 6.26cm, 5.82cm for Shovel fishing, 8.09cm for trap, and expressed big difference by fishery. It needs necessary various kinds of Octopus resource management actions and methods in continuous use. Specially, Fishing force increased by fishing automation system, so the reduction of fishing force is needed to increased by fishing force. Government support and fishermen's self-conscious of resource management is needed.

• 수산해양기술연구
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• 제53권4호
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• pp.357-362
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• 2017

The purpose of this study is to analyze the efficiency of distant-water longline fishing vessels in the Pacific Ocean and the gap in efficiencies among individual vessels. In order to estimate the efficiency, the dependent variable is set as an amount of catch and independent variables include number of crew, number of hooks, number of vessel size, and vessels engine power associated with fishing activities of distant water longline fisheries. Analytical result was shown as follows: first, the average efficiency of distant-water longline fishing vessels in the Pacific Ocean was found to be 94%. Second, the number of hooks were found to be statistically significant in each input variable and the appropriate control of the number of hooks would be expected to have a positive effect on the efficiency. Third, the relationship between the age of a vessel and the efficiency was not found statistically.