• Korean Journal of Ichthyology
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• v.20 no.2
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• pp.105-111
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• 2008

A pelagic tuna longline research cruise in the eastern and central Pacific Ocean from September to October of 2006 was conducted to compare catch rates with the use of different hook type and bait combinations. Traditional tuna hooks (J 4) and three circle hook types (C15, C16, C18), along with five bait types (chub mackerel (CM), jack mackerel (JM), milkfish (MF), sardine (SD), and squid (SQ)) and hook number as a proxy for hook depth were evaluated for their effect on bigeye tuna catch rates (fish per 1,000 hooks) using Generalized Linear Models (GLMs). Results from 28 sets indicated significant differences in bigeye catch rates between individual longline sets and hook number. The GLM explained 33% of the deviance in bigeye catch rates with these two factors. An alternative model formulation included bait type which had a small effect (explaining 2.7% of the deviance) on catch rates. Hook type had a negligible and non-significant effect in the GLMs. These results indicate that all of the hooks and baits tested are equally effective at catching bigeye tuna and that hook number (depth) was the paramount operational factor in explaining bigeye tuna catch rates.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.15 no.4
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• pp.312-316
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• 1982

With an object to obtain an indication on the efficiency of the saury baits for tuna longline, frequencies of the saury heads found in the tuna stomachs were analysed by the equations developed from tile binomial distribution. Four factors were introduced into the equations : The hooking rate, p; rate of not being hooked q; rate of the effective baits retained in the stomachs of the captured tuna r; and the rate of tile previously taken baits retained in the tuna stomachs, t. The best estimates of $\frac{p}{p+q^t}$ and r are empirically obtained as follows. Yellowfin tuna: $\frac{p}{p+q^t}$=0.789, r=0.598 Bigeye tuna: $\frac{p}{p+q^t}$=0.810 r=0.608, Albacore tun : $\frac{p}{p+q^t}$=0.838, r=0.621.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.15 no.4
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• pp.317-322
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• 1982

The biting behaviors of tuna were studied based on the remains of saury (Cololabis saira), which was used as bait, in the stomach contents of tuna. The saury remains were classified into four segmental groups (A-segment: Whole fish; B-segment: anterior partion with head: C-segment: middlepart without both head and tail: D-segment : posterior part without head). The tuna stomachs were independently named and grouped into three subsamples according to bait segments remaining in the stomach. The subsamples have the extra number of the stomach-naming segments and the distributions of the bait tegments are biased from tile random distribution. The distribution of the bait segments except the extra segments are hypothetically assumed to be random, and was subjected to the chi-square test of significance. The inferred conclusions are as follows:1. Most of the tuna having the B-segment had previously taken the C and/or D-segment. 2. The catchability of the yellowfin tuna having the B-segment seems higher than that of the fish having the A-segment in the stomach. 3. Tuna which had two or more bait heads should have taken the extra bait heads without being hooked detaching the head from the hook by biting the Posterior porting of tile bait.

• Environmental and Resource Economics Review
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• v.28 no.3
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• pp.415-435
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• 2019

The purpose of this study is to analyze the returns to scale by estimating the bigeye tuna production function of Korean distant longline fisheries in WCFPC waters. In the analysis, number of crews, vessel tonnage, number of hooks, and bigeye tuna biomass are used as input variables and the catch amount of bigeye tuna is used as an output variable in the Cobb-Douglas production function. Prior to the function estimation, the biomass of bigeye tuna was estimated by the Bayesian state-space model. Results showed that the fixed effect model was selected based on the hausman test, and vessel tonnage, hooks, and biomass would have direct effects on the catch amount. In addition, it was shown that the bigeye tuna distant longline fisheries in WCFPC water would have increasing returns to scale.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.39 no.4
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• pp.305-317
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• 2003

Underwater shape and hook depth in tuna longline gear are important factors to decide fishing performance. It also should be considered that management and analysis of hooked rate data from hooked fish species and sizes, and each fishing would be used as a reference data in the future fishing. In this research, after analyzing underwater shape of tuna longline gear by current direction and speed using simulation, experiments were executed in flume tank to verify accuracy of the analysis. Also using the depth of each hook from the simulation, a database system was setup to process the data of bait and hooked fish species. The results were as follows；1. When the attack angle and the shortening rate are fixed, a decrease of the hook depth is proportion to an increase of current speed. 2. When the shortening rate and current speed are fixed, a decrease of hook depth is proportion to an increase of attack angle. 3. When the attack angle and velocity of flow are fixed, a decrease of hook depth is proportion to an increase of shortening rate 4. As a result of comparison between the underwater shape by simulation and that by model gear, the result of the simulation was very close to that of model gear within $$ {\pm}3%$$ 3% error range. 5. In this research, hooked rate database system using hook depth of simulation can analyze the species and size of fish by the parameter; bait. hook depth, so It could be helpful to manage and analyze the hooked data on the field.

• Proceedings of the Korean Aquaculture Society Conference
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• 2006.05a
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• pp.206-207
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• 2006

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