• Korean Journal of Fisheries and Aquatic Sciences
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• v.42 no.5
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• pp.518-522
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• 2009

The mesh selectivity of drift gill net for yellow croaker (Larimichthys polyactis) was examined in field experiments with six different net mesh size (40, 45, 50, 55, 60 and 65 mm) from April to December, 2008 in the northwestern coastal waters of Gageo-do, Korea. The total catch of 8,091 consisted of yellow croaker (n=7,574; 89.5% of total catch), common mackerel (n=162; 4.8%) and other species (n=355; 5.8%). The selectivity curve for the small size yellow croaker was fit by Kitahara's method to the polynomial equation S(R)=exp{($-0.552R^3$+$4.927R^2$-11.591R+9.320)-6.717}. The optimal mesh size for 50% retention for minimum landing size(191mm) of yellow croaker was estimated as 51.1 mm. This is very similar to the current drift net mesh size used in Gageo-do.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.50 no.3
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• pp.368-377
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• 2014

Small yellow croaker is one of the important stocks in Korean waters. In this study, we conducted sea trials to estimate optimum height of a drift gill net for effective fishing of small yellow croaker. In the trial using existing net which has 9.2m in height, there was 22 species (1,180 fishes, 99.9kg) caught. The catch (in individuals) of small yellow croaker, especially larger fishes (over 22cm in FL), was higher as part of net height is higher, while the number of species bycaught and the catch of those species were higher as part of net height is lower. In the trial using extension net which has 18.4m in height, there was 27 species (2,030 fishes, 151.7kg). It showed same pattern with existing net in the section I to III, however, in the section IV which is over 13.8m of net height, the catch sharply decreased. The number of species bycaught and the catch of those species using extension net were also same as results using existing net. It showed that section III (9.2-13.8m) where is upper-middle part of the net has caught most of catch and large fishes having over 22cm in length. Through these results, it is judged that the setting depth of the net where is 4.6-13.8m above the sea bottom is the best to reduce bycatch and catch much more large size fishes, and the catch per net is proportional to filtering area of net. Therefore the Fisheries Resource Management Act (the clause 1, article 10) on the amount of usage for offshore drift gill net need to be considered not only length of a net but also net height.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.41 no.3
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• pp.199-206
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• 2005

As the basic study about improvement of yellow croaker drift gill net fishing implement and development of the fishing system, this study drew problem after synthetically analyzing hauling system of yellow croaker drift gill net used in the coast of Chuja Island and tested several characters and analyzed in hauling process with 5 step net hauler model for improving the problem. The analysis results are as follows. When the angle between axises of drum centers was small, it showed the tendency that hauling time was fast. Hauling time was faster when drum was 5 step rather than 3 step. When drum was 5 step, slippery phenomenon was small and hauling was stable. Tension was larger when drum was 5 step rather than 3 step. When drum was 5 step, the range of change of the maximum and minimum value was small and hauling was stable. When drum was 3 step, there was following formula between hauling time ($Ht_3$) and angle between axises of drum centers ($A_g$) $Ht_3$ : ($7.15Hs^{-0.81}$) $A_g^{-0.81}$, when drum was 5 step there was following formula.$Ht_5$ : ($6.45Hs^{-0.75}$) $A_g0.10$, here, Hs is hauling speed. When drum was 3 step and hauling speed was 28cm/sec, tension was $T=0.08A_8^3-1.60A_g^3-0.49A_g+369.56(r=0.99)$, when drum was 5 step, tension was, $T=-0.01A_g^3+1.96A_g^2-34.05A_g+414.58$ (r-0.99), here, T was tension(g).

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.48 no.1
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• pp.10-19
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• 2012

The mesh selectivity of a drift net for yellow croaker (Larimichthys polyactis) was examined in field experiments with six different net mesh size (40, 45, 50, 55, 60 and 65mm) from April to December, 2008 in the coastal areas of Jeollanam-do in Korea. The total catch of 6,748 consisted of yellow croaker (n=6,310; 89.1% of total catch), common mackerel (n=158; 5.6%) and other species (n=280; 9.6%). The selectivity curve for yellow croaker was fit by the models of selectivity curve in SELECT method. The optimal mesh size for 50% retention for minimum landing size (191mm) of yellow croaker was estimated as 49.6mm-51mm by selectivity curves. And the bi-normal model for the selectivity curve was found to fit the data best.

• Journal of Fisheries and Marine Sciences Education
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• v.26 no.1
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• pp.98-107
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• 2014

As part of a series of studies about improving yellow croaker drift gill net fishing gear and the development of a labor-saving fishing system, we installed a labor-saving-type, five-step-drum net hauler, and a triple-V-type net hauler in 108 Daeheung-ho, a fishing boat which operates drift gill nets for yellow croakers mainly in the sea near Chu-ja Island. Net damage with the labor-saving-type, five-step-drum net hauler is lower than for the triple-V-type net hauler. In addition, there was a reduction in the standard operational crew of two people. The lead time for hauling the labor-saving net was approximately 10% and 19.2% less than for hauling the triple-V-type net hauler and for hauling by hand, respectively. It was found that there were fewer slip in fishing gear and less damage to the wing of the drum as well as less damage to the fish when the labor-saving-type, five-step-drum net hauler was used than when the triple-V-type net hauler was used. In the survey, the lead time for hauling the net was approximately 21.6% and 45.2% more effective than hauling with the triple-V-type net hauler and hauling by hand, respectively. The crew was reduced by approximately 18.2% and 25% than when hauling with the triple-V-type net hauler and hauling by hand, respectively. In addition, cessation of operation and damage to the fish were reduced when compared to the triple-V-type net hauler and hauling by hand.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.46 no.1
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• pp.10-19
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• 2010

As a series of studies about improvement of yellow croaker drift gill net fishing gear and development of the labor saving fishing system, this study analyzed the behavior characteristics of fishing gear, which does use three types of different sinker materials in the field tests. The result of maritime performance test indicated that the fishing gear which used the lead reached the maximum depth and bio ceramics hauled to the surface of water the fastest. The correlation between the sinking time (St) and depth (Dsl, Dsc, Dsb) of maritime performance test can be shown such experimental equations as Dsl=2.70St - 0.75, Dsc = 2.38St - 1.15, Dsb = 1.77St - 4.00. The correlation between the hauling time (Ht) and depth (Dhl, Dhc, Dhb) of maritime performance test can be shown such experimental equations as and Dhl = 7.88Ht + 35.48, Dhc = 7.80Ht + 40.01, Dhb = 7.95Ht + 36.44.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.51 no.4
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• pp.535-544
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• 2015

Yield per recruit model is the most popular method for fisheries stock assessment. However, stock assessment using yield per recruit model can lead to recruitment overfishing as this model only considers the maximum yield per recruit without spawning biomass for reproduction. For this reason, spawning biomass per recruit model which reveals variations of spawning stock biomass per fishing mortality (F) and age at first capture ($t_c$) is considered as more proper method for stock assessment. There are mainly two methods for spawning biomass per recruit model known as age specific selectivity method and knife-edged selectivity method. In the knife-edged selectivity method, the spawning biomass per recruit has been often calculated using biomass per recruit value by multiplying the maturity ratio of the recruited age. But the maturity ratio in the previous method was not considered properly in previous studies. Therefore, a new method of the knife-edged selectivity model was suggested in this study using a weighted average of the maturity ratio for ages from the first capture to the lifespan. The optimum fishing mortality in terms of $F_{35%}$ which was obtained from the new method was compared to the old method for small yellow croaker stock in Korea. The value of $F_{35%}$ using the new knife-edged selectivity model was 0.302/year and the value using the old model was 0.349/year. However, the value of $F_{35%}$ using the age specific selectivity model was estimated as 0.320/year which was closer to the value from the new knife-edged selectivity model.