• Korean Journal of Ichthyology
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• v.17 no.4
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• pp.279-286
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• 2005

The fish species composition and its seasonal variation of the middle East Sea of Korea were investigated from May 2004 to January 2005 using gill and set nets. A total of 59 species of fishes belonging to 31 families in 11 orders were identified in the gill and set nets; 33 species in 15 families and 6 orders were collected by the gill net, and 36 species in 26 families and 10 orders were collected by the set net. Among the fishes collected by gill net, the order Scorpaeniformes was dominant; the number of species as well as individuals was highest in summer; the biomass was highest in winter. However, in fishes collected by set net, the order Perciformes was dominant, the number of species was highest in autumn, the number of individuals was highest in spring, and the biomass was highest in winter. The fish composition of the middle East Sea differed considerably from that of the south East Sea, especially in the species composition of the order Scorpaeniformes and Pleuronectiformes. Principal component analyses for each net showed that the fish species composition depends on the kind of net used, even though the investigation was carried out in the same area and at the same time.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.40 no.3
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• pp.176-181
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• 2004

In order to examine the mesh selectivity and optimum mesh size of trap nets for purple shell, Rapane venosa, the field experiments were carried out during Jun. 27 to 29, 2003 at the coastal area of Mal-Do, Kunsan, Jeonbuk province. The experimental fishing gears were used in two set of trap nets, which one set was consisted of 210 trap nets that were coverd with 35mm, 50mm and 65mm 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 trap nets for purple shell was 1,682, and it was consisted of 1,268 purple shells (75.4%), 225 Glossaulax reiniana (13.4%), 113 green lings (6.7%) and 76 other fishes (4.5%). 2. The value of maximum 1/m on the mesh selectivity curve was estimated at 1.79. 3. The value of 1/m on the 50% selection range was estimated at 1.24${\sim}$2.72, and the selection width was 1.48.. 4. The optimum mesh size of trap nets for purple shell based on the catch prohibition shell height(50mm) was estimated 40.3mm, and the 50% selection range of shell height of purple shell was 50.0${\sim}$109.6mm.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.48 no.4
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• pp.301-309
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• 2012

A net-assembling company for gill net fishing gears makes a design based on the size of nets provided and determines floats, types of weights, and numbers. In addition, through the accurate examination of net weights in the process of fishing gear designing, it can prevent an excessive use of designing costs. The weight of twine can be easily calculated by its thickness differences, but the weight of netting has errors to be calibrated since the weight of netting is not changing exponentially with the changes of number and size of meshes. This study aims to suggest and empirically analyze the methods for estimating the weights of netting in accordance with the changes of number, size and thickness of meshes for a sound management of netting and net-assembling companies. Results indicated that the method using the knots and legs of netting was not practically usable because the errors were increased as the number of mesh increased. However, the method using netting area shown its usage potentiality with the calibration of the increasing ratio of mesh numbers.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.39 no.1
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• pp.56-62
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• 2003

To investigate the entrapping behavior of blue crab, rock shell and green ling, which are mainly caught with the other trap nets in the coastal area of Yellow Sea, by the using duration of trap nets through the water tank experiment. We select the three kinds of trap nets which have different using duration such as new, 6 months and 12 months used one, and observe the entrapping ratio into the trap nets, respectively. In the mean while, in order to obtain the basic data for the estimate of mesh selectivity of the other trap nets, the entrapping behavior into the trap nets for green ling which has high activity compared to blue crab and rock shell, are examined to the three kinds of mesh size (35mm, 50mm and 65mm). The results are as follows ; 1. The mean entrapping ratio of blue crab by the using duration of trap nets in high with 4.4 fishes (44.0%) in the 6 months used one, become lower with 2.9 fishes (28.0%) in the new one, and with 2.0 fishes (20.0%) in the 12 months used one. 2. The mean entrapping ratio of rock shell by the using duration of trap nets in high with 7.3 fishes (36.7%) in the new one, and become lower with 7.2 fishes (35.8%) in the 6 months used one, and with 5.7 fishes (28.3%) in the 12 months used one. 3. The mean entrapping ratio of green ling by the using duration of trap nets in high with 3.4 fishes (34.0%) in the 6 months used one, and become lower with 3.0 fishes (30.0%) in the new one, and with 2.8 fishes (28.0%) in the 12 months used one. 4. The mean residual ratio of green ling by the mesh size of trap nets is high with 2.4 fishes (24.0%) in the 35mm mesh size, and become lower with 2.2 fishes (22.0%) in the 50mm mesh size and 2.0 fishes (20.0%) in the 65mm mesh size.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.42 no.1
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• pp.78-82
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• 2009

We describe a catch experiment and the size selectivity of gill nets for male Japanese sandfish (Arctoscopus japonicus) caught near Gosung, Korea. The experiment, which was conducted between October and December 2007, examined six different mesh sizes: 36.4, 39.4, 45.5, 51.5, 53.0, and 57.6 mm. The catch was mostly Japanese sandfish (91.3%) and some others (8.7%). More male Japanese sandfish were caught with smaller mesh sizes and more females with larger mesh sizes. Relationships between the weight and fork length of the male and female Japanese sandfish were obtained. The relationship between the catch (Y) and mesh size of the gill net (X) was $Y=0.1773X^3-5.3753X^2+40.042X+26.846$ ($R^2=0.99$). The selection curve for male Japanese sandfish caught in the experiment was fit, via Kitahara's method, to a polynomial equation, which was $s(R={\exp}\{(-2.1391\;R^3+24.294\;R^2-88.289\;R+105.5)-5.180\}$, where R=l/m, and l and m are the fork length and mesh size, respectively.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.52 no.4
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• pp.281-289
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• 2016

Spinyhead sculpin Dasycottus setiger, a species of cold water fish, is distributed along the eastern coastal waters of Korea. A series of fishing experiments was carried out in the waters near Uljin from June, 2002 to November, 2004, using the experimental monofilament gill nets of different mesh sizes (82.2, 89.4, 104.8, and 120.2 mm) to describe the selectivity of the gill net for the fish. The SELECT (Share Each Length's Catch Total) analysis with maximum likelihood method was applied to fit the different functional models (normal, lognormal, and bi-normal models) for selection curves to the catch data. The bi-normal model with the fixed relative fishing intensity was selected as the best-fit selection curve by AIC (Akaike's Information Criterion) comparison. For the best-fit selection curve, the optimum relative length (the ratio of fish total length to mesh size) with the maximum efficiency and the selection range ($R_{50%,large}-R_{50%,small}$) of 50% retention were obtained as 2.363 and 0.851, respectively. The ratios of body girth to mesh perimeter at 100% retention where the selection curve of each mesh size represented the optimum total length were calculated as the range of 0.86 ~ 0.87.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.53 no.4
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• pp.317-326
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• 2017

Comparative fishing experiments were conducted in the eastern coastal waters near Uljin, Korea from 2002 to 2004, using the experimental trammel nets to estimate the selectivity for spinyhead sculpin Dasycottus setiger. The inner panels of the nets were made of nylon monofilament with four mesh sizes (82.2, 89.4, 104.8, and 120.2 mm) while its two outer panels were made of twisted nylon multifilament with a mesh size of 510 mm. The SELECT (Share Each Length's Catch Total) procedure with maximum likelihood method was applied to obtain a master selection curve. The different functional models (normal, lognormal, bi-normal, and logistic model) were fitted to the catch data. The lognormal model with the fixed relative fishing intensity was chosen as the best-fitted selection curve through comparison of model deviance and AIC (Akaike's Information Criterion). The optimum relative length (the ratio of fish total length to mesh size) with the maximum relative efficiency was obtained as 2.492.

• Animal cells and systems
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• v.15 no.1
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• pp.79-84
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• 2011

The status of J stock minke whales (Balaenoptera acutorostrata) was assessed using potential biological removal (PBR) and mortality data. Using the estimated abundance of minke whales in this area (6260; CV = 0.212), the minimum population estimate of the stock was estimated as 5247. The PBR for J stock minke whales was calculated as 52.5 individuals using the minimum population estimate (5247), one-half of the maximum theoretical net productivity rate (0.02) and the recovery factor (0.5). The estimated mean annual level of anthropogenic mortality was 270.4 individuals. Thus, the status of this stock was considered as strategic. However, fortunately, the abundance of this population in the East Sea from 2000 to 2008 showed an increasing trend (rate of increase 0.0488; annual rate of increase 5.0%) although it is not statistically significant (P > 0.05). The primary sources of anthropogenic mortality were bycatch (set nets, pots and gill nets) and illegal catch. Because of the status of this population, it is urgently necessary to reduce the amount of bycatch and illegal catch of minke whales. Further study needs to use population health and viability analysis for investigating the long-term survival of this population more clearly.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.30 no.6
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• pp.916-922
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• 1997

This paper attempted to estimate mesh selectivity of gill nets for neon flying squid in the north Pacific Ocean. The 11 linear regressions, (P<0.05) were obtained using the data on catch ratios derived from mesh size combinations between two slightly different mesh sizes of 12 kinds of research gillnet (namely 33, 37, 42, 48, 55, 63, 72. 76, 86, 96, 105 and 115 mm in stretched mesh size). There was an increase in the optimum length with the increase in mesh size but standard deviation showed somewhat increase with the increase in the mesh size. The selectivity curves were well fitted to the length frequency distributions obtained from samples for the mesh sizes from 48 mm through 86 mm. For the mesh sizes of 33, 37 and 42 mm the DML (Dorsal Mantle Length) compositions were distributed towards the right hand-limb of the curves. The DML distributions from the 96 mm and larger meshes showed a trend towards the left hand-limb of the curves. The selectivity curves for different mesh sizes indicate that large mesh sizes catch a greater size range of squid, and the gill net fishery in the north Pacific Ocean captures effectively neon flying squid within the range of $9\~43cm$ DML.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.8 no.1
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• pp.11-19
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• 1975

Yellow croaker, Pseudosciaena manchurica Jordan et Thompson, in the Yellow Sea and the East China Sea are subjected to be caught by trawl nets, stow nets and gill nets throughout the year. Monthly indices of population size are calculated. Mathematic models (I) were used in order to determine catchability coefficient, natural mortality, fishing mortality, coefficient coefficient of the fishing ground and dispersion coefficient from the fishing ground. The results are summarized as follows: 1971 1972 1973 $$Catchability\;coefficient\;(C)=1.9369\times10^{-5}\;7.5459\times10^{-6}\;1.2670\times10^{-5}$$ Natural mortality (M) = 0.1645 0.6152 0.4367 Population for the first half season (February 1 to May 31) 1971 1972 1973 Initial\;population=\;107,100M/T 209,100M/T 214,400M/T Dispersion=83,000' 159,700' 133,400' Natural mortailty= 4,700' 32.700' 19,100' Final population= 2,800' 4,500' 49,000' Population for the latter half season (June 1st to the following January 31st) 1971 1972 1973 Initial population= 44,500M/T 67,500M/T 83,800MT Recruitment= 19,000' 183,900' 67,100' Natural mortality= 5,900' 67,900' 38,500' Final population= 37,000' 168,300' 92,400'.