• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.44 no.3
• /
• pp.194-206
• /
• 2008

This study standardized catch per unit effort(CPUE) of the Korean longline fishery, which has been used to assess the status of stock as an index of abundance, for bigeye and yellowfin tunas in the Indian Ocean. The Generalized Linear Model(GLM) was used to analyze the fishery data, which were catch in number and effort data collected each month from 1971 to 2007 by $5\;{\times}\;5$ degree of latitude and longitude. Explanatory variables for the GLM analysis were year, month, fishing area, number of hooks between floats(HBF), and environment factors. The HBF was divided into three classes while the area was divided into eight subareas. Although sea surface temperature(SST) and southern oscillation index(SOI) were considered as environmental factors, only SST was used to build a model based on statistical significance. Standardized CPUE for yellowfin tuna showed a declining trend, while nominal CPUE for the species showed an increasing trend.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.49 no.4
• /
• pp.500-504
• /
• 2013

A total of 24 juvenile specimens of Thunnus tonggol (5.45~7.26mm in total length) of the Sombridae were collected from the southeast sea of Jeju Island during 26~30 July, 2013. Twenty-four specimens identified T. tonggol have melanophores distributed on the 1st dorsal-fin rays, the dorsal of head and vetral side. Three individulas were identified using mitochondrial DNA cytochrome oxidase submit 1 (CO1) sequences (452 base pairs). All were identified as T. tonggol, their mtCO1 sequences being consistent with those of Thunnus tonggol (d=0.000), followed by Thunnus albacares (d=0.002) and Thunnus obesus (d=0.007).

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.56 no.4
• /
• pp.363-372
• /
• 2023

This study was developed to prepare hamburger steak (HS), wantang soup (WS), and tomato soup (TS) for senior-friendly seafood's (SFS) using bigeye tuna Thunnus obesus, and to investigate their quality characteristics. All data were presented in the order of HS, WS, and TS. The hardness values were 298.9×1.0³, 47.1×1.0³ and 14.9 ×1.0³ N/m², respectively. The viscosity of TS was 2,856 mPa·s. The protein contents were 13.8, 11.7, and 9.7 g/100 g, respectively. The fat-soluble vitamins content were as follows: vitamin A 21.88, 5.03, and 23.72 ㎍RAE/100 g; vitamin D 1.15, ND, and 1.81 ㎍/100 g, respectively. The water soluble vitamins contents were as follows: vitamin C 47.22, 32.83 and 37.01 mg/100 g; vitamin B₂ 0.17, 0.11 and 0.10 mg/100 g; vitamin B₃ 34.87, 34.76 and 54.62 mgNE/100 g. The Ca contents were 15.9, 16.8, 28.9 mg/100 g, and the K contents were 383.8, 167.4, and 300.0 mg/100 g, respectively. The dietary fiber was 0.04, 0.07 and 0.08 g/100 g, respectively. Escherichia coli was not detected in any of the products. These results suggest that the products should be classified as follows, based on their appropriateness as SFS: HS, WS and TS.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.43 no.6
• /
• pp.740-746
• /
• 2010

This study standardized the catch per unit effort (CPUE) of bigeye tuna (Thunnus obesus) caught by the Korean longline fishery in the Pacific Ocean. The study used a general linear model (GLM) to standardize the CPUE using catch and effort data aggregated by year, month, and $5{\times}5$ degrees of latitude and longitude in the tropical Pacific Ocean from 1982 to 2008 (except for 1988 and 1989). Explanatory variables in the GLM analysis included year, month, subtropical area, and number of hooks between floats (HBF). The study area and HBF were subdivided into three subtropical areas and six classes, respectively. During the study period, the standardized CPUE was significantly related to the nominal CPUE. The standardized CPUE declined sharply, as compared to the nominal CPUE, after the mid 1990s. In particular, the decline in the standardized CPUE in all subtropical areas in the 2000s was clearer than that of the nominal CPUE.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.27 no.4
• /
• pp.225-231
• /
• 1991

In order to suggest the useful information on the fishing ground of the bigeye tuna Thunnus obesus(LOWE), a data base system was formed with catch data of the Korean tuna long liners during from 1975 to 1987 by using a set of 16 bits personal computer. This data base was constructed of the handling program and 4 types of data file processed from the monthly and yearly catch data of the whole tunas and the bigeye tuna. And when the system was started, the map of one among various Oceans such as the Pacific, the Atlantic and the Indian Ocean. is drawn on the monitor. And then the catch rates of the whole tunas or the catch ratios of bigeye tunas are indicated by the figured symbols and the colors on the sea divisions of 5$^{\circ}$ space of longitude and latitude respectively at the same time. Also this system has the preestimating program on the catch rates of the whole tunas and the bigeye tuna in the desired month and sea divisions. In the results than this data base system was handled and tested, very useful informations were obtained for the detection of tunas, especially bigeye tuna, and the preestimation was possible in a desired level.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.47 no.4
• /
• pp.344-355
• /
• 2011

We conducted experiments to compare the catch rate of bigeye tuna and yellowfin tuna between circle hooks and straight shank hook in the Korean tuna longline fishery at the eastern and central Pacific Ocean from 2005 to 2007. We analyzed difference of fork length, survival and hooking location between a circle hook and a straight shank hook for both tunas, respectively. There was no difference in the mean fork length size of yellowfin tuna caught on the two type of hook but bigeye tuna was significant. In case of survival, there was no difference between two hook type, but the difference of hooking location was significant for both species. We also analyzed to find determinants of both tunas catch rate using generalized linear models (GLMs) which were used latitude, longitude, year, month, depth, hook type, bait type and so on as independent variables. Spatial factors, latitude and longitude, and temporal factors, year and month, affected catch rate of bigeye tuna and yellowfin tuna. And also, depth such as a marine environment factor was influenced on catch rate.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.51 no.3
• /
• pp.414-423
• /
• 2015

Fishing trend and characteristics of Korean tuna purse seine fishery in the Pacific Ocean were investigated using logbook data compiled from captain onboard and the statistical data from 1980 to 2013. The historical catch of this fishery had sharply increased since mid-1980s, and it has shown fluctuations with about 2-3 hundred thousands, whereas the catch per number of vessel has steadily increased with fluctuations since commencing this fishery. As for the proportion of catch by set type, unassociated type had increased from the mid-1980s to the end of 1990s, and then has decreased up to 2010s. Associated type had decreased continually to the end of 1990s, however, it started to increase since the beginning of 2000s. As for the catch proportion of set type by main species, those of skipjack tuna and bigeye tuna showed higher in the associated type, whereas that of yellowfin tuna has the highest proportion in the unassociated type. Fishing distribution of Korean tuna purse seine fishery was concentrated on the area of $5^{\circ}N{\sim}10^{\circ}S$ and $140^{\circ}E{\sim}180^{\circ}$ through the decades. The monthly catch distribution by longitudinal zone of Korean tuna purse seine fishery expanded the most further to the eastward in September to October.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.30 no.5
• /
• pp.719-729
• /
• 1997

Stomach contents of bigeye tuna, Thunnus obesus, and yellowfin tuna, Thunnus albacares, caught by longlining in the western tropical Pacific were analyzed to examine their foods and to compare their feeding behavior. The food species of both bigeye and yellowfin tunas were primarily fishes, crustaceans, and cephalopods. A total of 15 fish, 6 crustacean, and 1 cephalopod species were identified from their stomach contents, of which lantern fish (Myctophum sp.) was the most important food for both tuna species. No significant differences in species composition of food items between bigeye and yellowfin tunas were observed, indicating that in the same habitat the tunas have a similar feeding behavior. However, while they showed a remarkable similarity in diet composition, significant quantitative differences on the basis of IRI values were observed in several diet species, such as Myctophidae, Alepisauridae, Oplophoridae, Gammaridae, and Onychoteuthidae.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.38 no.3
• /
• pp.196-204
• /
• 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.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.58 no.4
• /
• pp.317-325
• /
• 2022

Korean tuna purse seine fishery in the Western and Central Pacific Ocean (WCPO) began to operate in earnest in the early 1980s. Since then, the total catch has shown an increasing trend and the target species are skipjack tuna (Katsuwonus pelamis), yellowfin tuna (Thunnus albacare) and bigeye tuna (Thunnus obesus). Based on the operational data of Korean tuna purse seine fishery from 2016 to 2020, the catch rates of target species (skipjack and yellowfin tunas) were analyzed by operation time for set types (free school and FAD sets). In the case of the free school sets, they were usually made from sunrise to sunset, and the catch rate was high before and after sunrise for skipjack tuna and before sunset for yellowfin tuna. On the other hand, for the FAD sets, more than 90% of them were made just before sunrise, and there were few operations during the daytime. The purpose of this study is to examine whether there are differences in the catch rate of skipjack and yellowfin tunas by operation time and by school type for Korean tuna purse seine fishery in the WCPO, which could be helpful in understanding its fishing characteristics and providing useful information for developing the stock indices of the target species.