• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.41 no.2
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• pp.95-100
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• 2005

In order to improve the gill nets for croaker, Miichthys miiuy which is proper to the fishermen's income ans fisheries resource management, we had studied to the net height of present gill nets (mesh size 160mm, 50 mesh in depth), experimental gill nets-I(mesh size 150mm, 68 mesh in depth) and experimental gill nets-II(mesh size 142mm, 75 mesh in depth) in wter using the gill nets design ans analysis simulation system, and then investigated and analyzed the catch efficiency of each gill nets through the field fishing experiments. The net height of emperimental gill nets-I and experimental gill nets-II in water were estimated respectively about 1.5 times and 1.3 times higher than present gill nets which the net height is about 3.5m as the results of simulation considering the current of fishing fields. Total number of croakers which were caught by the persent gill nets was 62(body length 300~1,200mm), total catch weight was 398.7kg (mean 0.6kg/sheet). Total number of croakers which were caught by the experimental gill nets- I was 68(body length 600~1,100mm), total catch weight was 391.6kg (mean 1.2kg/sheet). Total number of croakers which were caught by the experimental gill nets-II was 28(body length 400~900mm), total catch weight was 99.2kg (mean 0.3kg/sheet).

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.49 no.2
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• pp.95-105
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• 2013

Physical characteristics of net filament were investigated to test the fishing capacity of gill nets due to the flexibility difference between nylon and biodegradable nets (PBS 95%+PBAT 5% and PBS 80%+PBAT 20%). In addition, a total of 16 fishing experiments were conducted in the coastal waters of Jeongja, Ulsan, from August 10 to October 20, 2011 and from September 11 to November 3, 2012. The test results showed that nylon net filament exhibited more flexibility than biodegradable net filament when they were wet. Accordingly, the longer submerged time, the more fishing capacity the nylon gill nets demonstrated in comparison with the biodegradable gill nets. A total of 16 species were caught in 2011 with the nylon gill nets (1,323 fishes, weighing 342,885g) and the biodegradable gill nets (958 fishes, weighing 236,857g). 15 species were caught in 2012 with the nylon gill nets (1,582 fishes, weighing 448,360g) and the biodegradable gill nets (1,431 fishes, weighing 406,590g). Thus catch weights and the number of fish caught produced by the nylon nets were 1.45 times and 1.38 times higher than those of the biodegradable nets produced in 2011, and 1.1 times and 1.11 times higher in 2012. A test on the target species, pointhead flounder (Cleisthenes pinetorum) has similar results. The flexibility of a net was proved to be related to the fishing capacity, and as a result, it is concluded that the higher flexibility, the higher fishing capacity.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.8 no.1
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• pp.7-10
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• 1975

The catches of mackerel by monofilament and multifilament net were compared by means of $x^2$ and t-test method. In order to improve the netting twine of drift nets, 6 shoots 5 different mesh and nylon-monofilament netting twines $(B\times2,\;C\;D,\;F,)$ and 2 shoe nylon-multifilament $(A\times2)$ which are using near the Jeju Island in contemporary days were used for the experiment. These gill no were connected in order of A, ,B, C, A, B, E, F and operated fly fishing boat Taeann Ho (7T) near sea of Jeju Ialand from May 1974 to August 1974. The results obtained are as follows: 1. B type nylon-monofilament gill nets were superior to nylon-multifilament gill nets in catch according to the result of $X^2$ test and t-test, and the catch ratio was $M_A:\;M_B=1:1.8$. 2. 75mm mesh size C, D nylon-monofilament gill nets were superior to 85mm mesh size nylonmonofilament gill nets, and their catch ratio were E, F: C, D=1:2.8. 3. The catch ratio C, D and E, F type nets were compared by means of t-teat, however could not recognized their relationship.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.39 no.1
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• pp.50-55
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• 2003

In order to study on the improvement of gill nets and trap nets fishing for the management of fisheries resource in the coastal area of Yellow Sea, we have investigated the general present condition of those fishing, and the actual fishing operation of gill nets for croaker and trap nets for rock shell which is called the the other trap nets, and then measured the body length of croaker and blue shell caught by their fishing vessels. The results are as follows ; 1. The total number of permission for coastal fishing are 12,944 cases, but the number of operation for coastal fishing are 7,558 cases in the coastal area of Yellow Sea. Among the total number of permission, the gill nets fishing are 5,154 cases with 39.8% but even so the number of operation are 3,724 cases, the trap nets fishing are 1,025 cases with 7.6% but even so the number of operation are 662 cases. On the fishing ratio, the gill nets and trap nets fishing are comparatively higher than the other fishing with 72.3% and 64.6%, respectively. 2. The main fishing period of gill nets for croaker is from the middle of July to early of September, and the main fishing grounds are sandymud bottom of 15-50m in depth around the islands of southern parts of western coastal area, and the fishing operation carry out 1∼2 times per day in flood tide and nets hauling conduct in 1∼2 hours after drifting with current. 3. The distribution range of body length of 139 croakers, which are caught in the gill nets, are 43.0∼120.0㎝ and the mode is 85.0㎝. 4. The main fishing period of trap nets for rock shell which is called the other trap nets is all the year round except the catching period of blue crab from early of September to the middle of October, and the main fishing ground are the sandymud bottom of 10∼20m in depth, and nets hauling conduct in next day after nets casting. 5. The distribution range of maximum carapace of 5,372 rock shells are 4.5∼8.5㎝ and the mode is 7.5㎝.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.40 no.3
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• pp.169-175
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• 2004

In order to examine the mesh selectivity and optimum mesh size of gill nets for croaker, Milichthys miiuy, the field experiments were carried out during Aug. 10 to 14, 2002 and Aug. 10 to 17, 2003 at the caostal area of Imja-Do, Shinan, Jeonnam province. The experimental fishing gears were used in two set of gill nets, which one set was consisted of 12 sheets of gill nets, and each set was connected alternatively 4 different sheets that were 129mm, 135mm, 144mm and 150mm in mesh size. The analysis of mesh selectivity curve was done by Kitahara's method. The results obtained are summerized as follows : 1. The total number of catch by the experimental fishing of gill nets for croaker was 719, and it was consisted of 526 croakers (73.1%), 168 blue crabs (23.4%), 17 harvest fishes (2.4%) and 8 other fishes (1.1%). 2. The value of maximum 1/m on the mesh selectivity curve was estimated at 6.91. 3. The value of 1/m on the 50% selection range was estimated at 5.62${\sim}$80.3, and the selection width was 2.41. 4. The optimum mesh size of gill nets for croaker was estimated 142mm, and the 50% selection range of total length of croaker was 798${\sim}$1,140mm.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.43 no.3
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• pp.169-175
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• 2007

To examine the mesh selectivity and optimum mesh size of gill nets for silver promfret Pampus argenteus, the field experiments were carried out during June 27th to July 3rd, 2005 at the coastal area of Imja island. The experimental gill nets for silver promfret were used in two set, which one set was consisted of 12 sheets, and each set was connected alternatively four defferent sheets those were 141mm, 148mm, 155mm and 164mm in mesh size. The analysis of mesh selectivity curve was done by Kitahara's method. The total number of fishes caught by experimental fishing of gill nets for silver promfret was 1,409, and it was consisted of 1,022 silver promfrets(72.5%), 123 croakers(8.7%), 70 red tongue soles(5.0%), 67 blue crabs(4.8%), 22 red seabreams(1.6%), and 105 other fishes(7.4%). The number of fishes caught by the mesh size was 244 at mesh 141mm(mean 6.8/sheet), 261 at mesh 148mm(mean 7.3/sheet), 295 at mesh 155mm(mean 8.2/sheet) and 222 at mesh 164mm(mean 6.2/sheet). The body weight of fishes caught by the mesh size was 102.1kg at mesh 141mm(mean 2.8kg/sheet), 112.9kg at mesh 148mm(mean 3.1kg/sheet), 132.8kg at mesh 155mm(mean 3.7kg/sheet), and 100.4kg at mesh 164mm(mean 2.8kg/sheet). The value of maximum l/m on mesh selectivity curve and the value of l/m on the selection range of 50% was estimated at 1.91 and from 1.63 to 2.23, respectively. Therefore, the optimum mesh size of gill nets for silver promfret was estimated 135mm, and the total length at the selection range of 50% was from 220mm to 301mm. But, it will be useful to use the mesh size of gill nets which is about 10-15% larger than the estimated optimum mesh size of gill nets considering the number of fishes caught, body length and body weight etc.

• Korean Journal of Ecology and Environment
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• v.53 no.2
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• pp.156-164
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• 2020

The accurate estimation of fish assemblages is highly dependent on the sampling gear used for sampling. We used data from 15 sampling sites along the Nakdong River, which is a large river in South Korea, to identify differences in assemblages and sizes of freshwater fishes collected with either cast nets or gill nets, the two most commonly used sampling gear in South Korea. The two gears differed in the fish assemblages they captured, with more species caught by gill nets. Further, due to its tighter mesh size, the cast net caught significantly smaller fishes than the gill nets(independent t-test, p<0.05). We found the cast net to be appropriate for species that inhabit shallow (less than 2 m) and open water, but inappropriate for deep water, habitats with plant beds, and nocturnal species. Thus, cast net sampling is not efficient in a large river environment, and a combination of sampling methods is more suitable for understanding fish assemblages in such habitats. In general, appropriate selection of fishing methods to specific habitats is necessary to improve data quality and minimize the misrepresentation of environmental conditions.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.36 no.6
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• pp.686-694
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• 2003

Monthly fish samples were collected using bottom gill nets and analyzed to study species composition and seasonal variation of fish assemblages in the coastal waters off Gadeok-do, Korea in 1998. During the study period, a total of 49 fish species representing 30 families were collected. The fish assemblages predominantly consisted of Limanda yokohamae, which accounted for $53.3\%$ of the number of individuals and $42.2\%$ in the biomass. The fish species, which had over 100 individuals, included Cynoglossus abbreviatus, Ditrema temmincki, Hexagrammos otakii, and Stephanolepis cirrhifer. These four species accounted for $24.1\%$ of the number of individuals and $24.3\%$ of the biomass. More fish species were collected in May and June than in any other months. The number of individuals and the amount of biomass peaked in April and May and reached a low in August. While the predominance of L. yokohamae caused the lowest species diversity by number of individuals in April, the predominance of Platycephalus indicus caused the lowest species diversity by biomass in July. Although gill nets show a strong selectivity for the target species or for size, gill nets can be used as an alternative fishing gear to collect fish in waters with rough bottoms, like rocky reefs, where other kinds of fishing gear such as trawls can not be used.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.48 no.4
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• pp.310-321
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• 2012

There are many studies of the biodegradable net for fishing to prevent marine pollution in Korea and the snow crab gill nets is developed effectively. Recently, the biodegradable gill net for fishes is being developed. This study is the experiment of the catch characteristics for the biodegradable flounder gill net. The 8 experiments were carried out using the nylon gill net and the biodegradable gill net in from August to October, 2011 in the southern East Sea. The results obtained from the above approaches are summarized as follows; A total of 16 species was caught with most dominant species of Cleisthenes pinetorum followed by Liparis tanakai, Glyptocephalus stelleri, Buccinum striatissimum and Dasycottus setiger. A total of catch of the nylon net was 342,885g and that of the biodegradable net was 236,857g. Thus catch of the nylon net was 1.45 times more than that of the biodegradable net. The length composition of Cleisthenes pinetorum, caught by the biodegradable net was very similar to that of nylon. As a result of analysis on the effect of submerged time, small fish escaped more easily than large fish as the submerged time is getting longer. And catches of the biodegradable net was less than the nylon net's as higher as wave height. Wave height was more influential factor for fishing capacity than submerged time based on the results of a comparison between catch difference of two kinds of gill nets and catch characteristics.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.38 no.2
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• pp.91-100
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• 2002

The field experiments were carried out to examine for the mesh selectivity in trammel net and optimum mesh size, during Aug. 10~13, Non 9~13 2000 in Jumunjin, Kangwon-Do and during Jun. 1~27 2001 in Suyong-Bay, Busan. The experiments in Jumunjin area were conducted by using trammel nets with seven different mesh sizes (60, 75, 90, 105, 135, 150, 180mm) and those in Suyong-Bay were done by using trammel nets and gill nets with three different mesh sizes (60, 75, 90mm) in order to compare two types of nets of same structure. The mesh selectivity analysis was done mainly with flat fish(Eopsetta grigorjewi) that was occupied 60% out of total catches. And the mesh selectivity was written by extension of Kitahara's method included master curve with function type. The results obtained are summarized as follows 1. Total number of catch by, trammel net was 2,331 and that of gill net was 1,433, and flat fishes occupied 59.8 ~60% in total catches. 2. The value of optimum l/m by, trammel net was higher about 0.1 than that of gill net according as trammel net was 2.56, and gill net was 2.47. 3. The 50% selection range by, trammel net was wider about 1.5 time than that of gill net according as trammel net was 1.88~3.36(1.48) and gill net was 2.00~3.02(1.02). 4. The optimum mesh size(OMS) was estimated that trammel net was about 141mm and gill net was about 132mm on first maturity length(FML) 265mm of flat fish. 5. On the optimum mesh size based on the first maturity length of flat fish, The 50% range by, trammel net was wider about 76mm than that of gill net according as trammel net was 265 mm~474mm and gill net was 265mm~398mm.