The study aims at a selective effect of the Grid and Window net in the shrimp beam trawl.The experimental trawling of the Proto type, Grid type and Grid and Window net type was performed in a sea area of Geo–je and Tong–yeong from Mar, 2006 to Apr, 2010. The obtained results are as follows; Catch per unit area (Number) of the Proto type net and Grid type net were 0.18/m2, 0.23/m2, respectively. The Grid type demonstrated 2.4% lower bycatch rate than the proto type (6.6% vs 4.2%, respectively). In addition, in terms of total weight, the bycatch rate of Grid type was 7.6% lower than the proto type (50.2% vs 42.6%, respectively). In the comparison of shrimp catch, the Proto type demonstrated better haul outcome (0.02 case/m2) than the Grid & Window type (0.02 case/m2). The Grid & Window net type demonstrated 16.4% lower bycatch rate than the Proto type (32.2% vs 48.6%, respectively). In addition, in terms of total weight, the bycatch rate of Grid & Window net type was 8.3% lower than the Proto type (85.9% vs 94.2% respectively).

To examine species composition, abundance and biomass of fishes in the northwestern East Sea of Russian EEZ, trawl survey were conducted at 31 sampling stations from 2006 to 2008. Also, trawl survey were conducted at 21 sampling stations in the southwestern East Sea of Korean EEZ from 2006 to 2008. A total of 67 fishes were collected in the northwestern East Sea of Russian EEZ, a total of 39 fishes were collected in the southwestern East Sea of Korean EEZ. Among them, a total of 53 fishes were collected in the northwestern East Sea of Russian EEZ only, and a total of 25 fishes were collected in the southwestern East Sea of Korean EEZ only. Mean abundance per area which caught by trawl survey in the northwestern East Sea ranged from a high of 116,478 inds./km2 in 2008 to a low of 19,737 inds./km2 in 2006. And mean abundance per area in the southwestern East Sea ranged from a high of 89,129 inds./km2 in 2006 to a low of 8,234 inds./km2 in 2008. Mean biomass per area which caught by trawl survey in the northwestern East Sea ranged from a high of 11,333 kg/km2 in 2008 to a low of 2,439 kg/km2 in 2006. And mean biomass per area in the southwestern East Sea ranged from a high of 6,273 kg/km2 in 2006 to a low of 1,062 kg/km2 in 2008. Cluster analysis, based on a Bray–Curtis similarity matrix of fourth root transformed data of number of species and individuals per area, showed division into three different groups by depth in the northwestern and southwestern East Sea.

The 1/5 scale–down model of the Bycatch Reduction Device (BRD) from an Argentinean demersal trawl was tested in a circulating water channel. The BRD is designed to help small Hake (merluza, merluccius hubbsi) to escape from a trawl. It is settled in front of a trawl codend, and is equipped with selection grids that help small fish to escape from the gear and guiding panels that help fish to meet with the grids. Bars of the grids are wires covered by the PVC and other parts of the BRD are made of net. When the velocity was less than 0.65 m/sec (2.81 Kont when translated to real towing speed) which is slow speed compared with real towing speed, position between an upper guiding panel and an upper selection grid were good to help small fish to escape. When the velocity was more than 0.8 m/sec (3.41 Knot when translated to real towing speed) which is similar to and faster than real towing speed, it was considered that small fish may have difficulties in escaping because the gap was not enough between an upper guiding panel and an upper selection grid. The lower selection grid was sat on the bottom of the tank without an angle due to the weight that it carries. Improvements were proposed to position the panels and the grids better.

Selectivity and by-catch are the main features used to define fish catch for fisheries management or to determine fishing gear efficiency. A fish girth distribution analysis was carried out to determine the retention rate of juveniles discarded and to establish common selectivity for a multispecies catch. Total body length, body weight, and girth of juvenile fish retained in the cod-end and cover net separately were collected using an 18-mm mesh cover net during 12 fishing trials with a 41-mm cod-end beam trawl. The by-catch weight ratio in the cod-end was twice that of the by-catch ratio in number. The 50% selectivity of body length and 50% girth of redfin velvet fish were not significantly different between the cod-end and cover net, whereas those of other fish species were significantly different between the cod-end and cover net. The difference in 50% selectivity girth of other fish between the cod-end and cover net was similar between cod-end mesh size and cover net mesh size. Furthermore, the difference in 50% body length selectivity of other fish between the cod-end and cover net was almost double the difference in girth. Girth selectivity in a multispecies catch using towed fishing gear was effectively used to determine fish and net mesh size.

The purpose of this study is to identify the flow resistance of the bottom pair trawl nets. The bottom pair trawl nets being used in fishing vessel (100G/T, 550ps) was selected as a full-scale net, and 1/10, 1/25 and 1/50 of the model nets were made. Converted into the full-scale net by Tauti’s modeling rule and Kim’s modeling rule, when resistance coefficient k of each net was calculated by substituting into above equation for flow resistance R and wall area of nets S values of each net v. Because resistant coefficient k decreases exponentially according as flow velocity v increases to make k cv-m, c and m values of each net were compared. As a result, as the model was smaller, c and m values was smaller in the two rule into standard of 1/10 model value, decrease degree of 1/25 model was almost same in the two rule, decrease degree of 1/50 model was very big in Tauti’s modeling rule. Therefore, in the result of experiment, because average of c and m values for similarly 1/10 and 1/25 model were given c=4.9 (kgf․s2/m4) and m=0.45, R (kgf) of bottom pair trawl net could show R =4.9Sv1.55 using these values. As in the order of cod-end, wing and bag part for 1/25 and 1/50 model net were removed in turn, measured flow resistance of each, converted into the full-scale, total resistance of the net and the resistance of each part net were calculated. The resistance ratio of each part for total net was not same in 1/25 and 1/50 model each other, but average of two nets was perfectly same area ratio of each part as the wing, bag and cod-end part was 43%, 45% and 12%. However, the resistance of each part divided area of the part, calculated the resistance of per unit area, wing and bag part were not big difference each other, while the resistance of cod-end part was very large.

The negative factors of fishery in environmental aspect of view are Greenhouse gas emission problems by high usage of fossil fuel, destruction of underwater ecosystem by bottom trawls, reduction of resources by fishing and damage of ecosystem diversity. Especially, the Greenhouse gas emission from fisheries is an important issue due to Cancún meeting, Mexico in 1992 and Kyoto protocol in 2005. However, the investigation on the GHG emissions from Korean fisheries did not much carry out. Therefore, the quantitative analysis of GHG emissions from Korean fishery industry is needed as a first step to find a relevant way to reduce GHG emissions from fisheries. The purpose of this research is to investigate which degree of GHG emitted from fishery. Here, we calculated the GHG emission from Korean bottom pair trawl fishery using the LCA (Life Cycle Assessment) method. The system boundary and input parameters for each process level are defined for LCA analysis. The fuel use coefficient of the fishery is also calculated. The GHG emissions from the representative fishes caught by bottom pair trawl will be dealt with. Furthermore, the GHG emissions for the edible weight of fishes are calculated with consideration to the different consuming areas and slaughtering process also. The results will be helpful to understand the circumstances of GHG emissions from Korean fisheries.

The angle of attack of a cambered otter board in a bottom trawl was estimated using a three-dimensional semi-analytic treatment of a towing cable (warp) system that was applied to the field experiments of a bottom trawl obtained by the Scanmar system. The equilibrium condition of the horizontal component and vertical component of forces was used to the three forces acting on the otter board in the horizontal plane. Those forces were the force on the warp at the bracket, hydrodynamic lift and drag forces on the otter board and the force on the hand rope attached just behind the otter board. Also the equilibrium of moment about the front edge of the otter board was used to find out the angle of attack of the cambered otter board. When the warp length was 120m and 180m long and the towing speed was between 1.23 and 1.90 m/s, the estimated angle of attack of the cambered otter board was ranged between 26.1° and 29.6°, respectively, though the maximum lift force was at the angle of attack 22.6°. The angle of attack of the otter board was tended to increase weakly with the longer length of warp (180 m) at the same towing speed in the experiment.

Seasonal variations in species composition of catches were explored using seasonal samples caught by shrimp beam trawl in the Geum river estuary in 2011. During the study period, total catches were collected 91 species as fish 47 species, crustacean 28 species, mollusca 4 species, gastropoda 5 species, shellfish 3 species and others 4 species. The dominant species were Exopalaemon carinicauda, Eriocheir leptognathus, Palaemon gravieri, Mugil cephalus, Acanthogobius hasta, Cynoglossus joyneri, Pennahia argentata and Coilia nasus. The amount of species in spring and summer was higher than in autumn. The diversity index (H') was 0.43~0.96, evenness index (EI) was 0.14~0.25, and richness index (RI) was 1.54~4.25. Using cluster analysis 91 species were divided into 4 groups. Group I appeared mainly in spring and summer. Group II appeared only in summer. Group III appeared in winter and spring, and Group IV in spring and autumn.

An active stimulating device, such as a fluttering net or canvas attached to the end of a cod end generating a shaking motion, could help to encourage the escape of juvenile fish positioned passively near the net. Field fishing trials using a shrimp beam trawl were carried out to examine the effect on the reduction of juvenile fish or other discard catch by generating a shaking movement of the cod end using an unbiased cap-like round canvas. The mean period of the shaking motion with the round canvas was 〜14 s, and the mean amplitude was 0.4 m as measured by peak event analysis and the global wavelet method. The bycatch of juvenile fish in 14 trials decreased by 〜30% and by 〜25% using a steady cod end for the total bycatch using a shaking cod end in the shrimp beam trawl, while the marketing catch was similar between steady and shaking cod ends. There was no difference in the body size of the shrimp or fish and species composition between the steady and shaking cod ends. Above results demonstrate a new method for bycatch reduction using an active stimulating device, although more detailed studies are needed.

Shrimp beam trawl fishery is one of the important coastal fisheries in Korea. It has a regulation to the length of beam (8m) and wing net (7m) of shrimp beam trawl that has been used in the district of Junlanam-do and Gyungsangnam-do. This regulation was made in relation to the size of shrimp beam trawler of 3-ton class at that time. Now the shrimp beam fishing vessel has a limit not greater than 5 tons in gross ton. Recently, with improvement of fishing industry and fishing vessel fishermen asked the expansion of the length of beam and wing net, therefore it is necessary to investigate the effect of lengthening the beam and wing net length. Three different beams (8m, 10m and 12m in length) and three different wing net (7m, 10m and 13m in length) were made and the experiment was conducted near Narodo of Goheng by two fishing vessels of 4.98 and 4.88 tons in gross ton between June 2011 and October 2012. When the length of wing net was increased from 7m to 10m and 13m, the relative catch ratio in total biomass was increased 25% and 79% for shrimp, (17% and 22% in total), respectively. And when the beam length was increased from 8m to 10m and 12m, the relative catch ratio was increased 35% and 84% for shrimp, (21% and 37% in total), respectively. The force exerted to the iron guide of inhauler’s with the beam length of 8m was about 30% greater than that with the beam length of 10m when hauling the shrimp beam trawl net.

The aims of this study are to access the status and problems and draft possible solutions of Korean trawl fishery in New Zealand sea. The main target fish species for Korean trawlers in this sea were barracouta, blue mackerel, hake, hoki, jack mackerel, ling, oreo, orange roughy, southern blue whiting, spiny dogfish, squid and silver warehou. The Korean trawl fishery are suffering from a supply of seaman, continuous increasing coast of the counter partner, repair of vessel and seaman supply. It may be useful for getting over these difficulties to build a new trawler with a automatic operation system.

The experiments were carried out to decide the selective fishing gear of the shrimp beam trawl fishery. The model nets were made of General type, Double-level type and Grid type. The model experiments were carried out to test opening efficiency and towing tension. The experimental tanks were the flume tank〔8.0L×2.8W×1.4H (m)〕and the towing tank〔85L×10W×3.5H (m)〕in National Fisheries Research and Development Institute. The full scale experiments were carried out to compare the selectivity of General type net, Double-level type net and Grid type net in the southern sea of korea.The vertical opening (net height) of the model nets can be expressed as a function of the towing velocity as the straight line. The towing tension of the model nets can be expressed as a function of the towing velocity as the parabola.The shrimp catching rates of upper cod end in Boryeong and tongyeong were 78%, 9% respectively, but the rates of lower cod end were 23%, 91% respectively. The number bycatch rates of General type and Grid type were 23%, 11% respectively, and the weight bycatch rates were 34%, 31% respectively. A selective shrimp beam trawl net is Grid type in korea coastal sea.

It was turned out by the beam trawl survey in 2009 that flora of three phylum 16 species and fauna of eight taxa 68 families 97 species were inhabited in the Seomjin River estuary and western coastal waters of Namhae island. Winter season showed the most various appearance of species with 63 species and markedly several kinds of algae species, while summer season showed the lowest number of species with 44 species. However, the indices of species diversity and evenness were highest in summer, and vice versa in winter. Major dominant species were Crangon hakodatei, Leiognathus nuchalis, Asterias amurensis, Thryssa kammalensis, Luidia quinaria, Amblychaeturichthys hexanema, Oratosquilla oratoria, Charybdis bimaculata, Cynoglossus joyneri, Pennahia agentata. The 10 dominant species occupied at 81.4% of catch in number and 49.0% of catch in weight. There were seasonal fluctuations and differences by station in the Seomjin River estuary and western coastal waters of Namhae island, which brought to the difference of length structures, that is, bigger-sized individuals of major dominant species at station A (near to river estuary) than station C (near to ocean). Species compositions by season and by station were separated to two groups. Winter season showed a separated species composition from other seasons and station A exhibited a different species composition from other stations, which was located at near to the Seomjin River estuary.

Experimental fishing was carried out to compare and analyze catch characteristics of shrimp beam trawl in a fishing area and a non-fishing area during the period of fishing season and off-fishing season in the coastal waters of Geoje. A commercial fishing boat (4.99 tons) was used for the test fishing. The amount of total catches were 14,654g in the fishing area and 12,359g in the non-fishing area, shrimp catches of non-fishing area were much greater than that of the fishing area during the period of off-fishing season (June and August). However, total catches were 27,670g in the fishing area and 33,004g in the non-fishing area, shrimp catches of fishing area were bigger than that of non-fishing area during the period of fishing season (October and December). On the results of the study, catches characteristics between fishing area and non-fishing area showed the reversed results for the period of fishing season and off-fishing season.

본 연구에서는 충남 연안에서 연안조망의 어획 특성을 파악하기 위하여, 2008년 3월부터 2009년 2월까지 매월 2∼4회 연안조망을 사용하여 어획조사를 실시하였다. 조사 해역은 동경 125도 50분∼126도 05분, 북위 36도 15분∼36도 25분의 해역이었고, 총 19목 63과 96종이 채집되었다. 그 중 어류가 54종, 갑각류가 27종, 복족류 및 이매패류가 9종, 그리고 두족류가 6종이었다. 생체량은 어류가 51.4 %로 가장 많았으며, 갑각류는 34.2 %를 차지하였다. 꽃새우는 7월~11월에 출현량이 많았고, 12월부터 5월까지는 적은 양이 출현하였다. 연안조망의 목표종인 꽃새우는 전체 어획물의 2.1 %로 낮은 채집 비율로 출현하였으며, 꽃새우 이외 어종의 부수적 어획물의 양적 비율이 높아, 꽃새우 어획이 부수어획으로 어획되는 종들의 수산자원에 미치는 영향이 클 것으로 판단된다.

Species composition and seasonal variation of aquatic organism in the marine ranchig ground of Taean, Korea were investigated using shrimp beam trawl from January to December 2010. A total of 99 species, 5,355,816ind./km2 and 84,697kg/km2 of aquatic organism were collected. Among them, fish include 9 orders 33 families 54 species, crustaceans include 2 orders 15 families 30 species, cephalopods consist of 3 orders 4 families 5 species, gastropods include 2 orders 3 families 4 species, echinoidea sp. include 1 order 2 families 2 species, bivalves were composed of 2 orders 2 families 2 species, and holothuroids include 1 family 1 order. According to the dominants by month, Palaemon gravieri was dominant in January, Cynoglossus joyneri was dominant in February, March, and June, and Hexagrammos otakii was dominant, in July. And Oratosquilla oratoria was dominant echinoidea sp. was dominant in April, May, and August and in September, October, November, and December. Cluster analysis based on species composition of the 38 most common species showed that the species were separated into 5 different groups. Group A was composed of species which were abundant in spring and summer, group B was composed of year-round residents, and group C was composed of species which were abundant in autumn.

진해만과 진주만에서 새우조망을 이용하여 2010년 4월부터 11월까지 총 4회의 어업조사가 이루어졌다. 조사기간 동안, 진해만에서는 총 116종이 어획되었고, 그 중 어류가 62종, 갑각류가 24종을 차지하였다. 진주만에서는 총 105종이 분류되었고, 그 중 어류가 56종, 갑각류가 31종 조사되었다. 진해만에서는 등가시치, 마루자주새우, 갯가재가 우점하였고, 진주만에서는 마루자주새우, 주둥치, 두점박이민꽃게 순으로 우점하였다. SOM을 이용한 군집유형화 결과, 진해만과 진주만의 군집구성이 계절에 따라 다르게 나타났다. 그룹1에 묶여진 진주만 조사정점들은 민새우, 대하 등 갑각류와 주둥치 쥐노래미 등의 어류가 우점하였다. 4월 조사는 해역에 상관없이 모든 정점이 그룹2에 묶였는데 마루자주새우, 검은띠불가사리, 꼼치 등의 밀도가 높았다. 그룹3에 묶여진 진주만의 6월 조사정점들은 두점박이민꽃게를 포함한 다양한 갑각류와 도다리, 돛양태, 쉬쉬망둑 등의 다양한 어류가 우점하였다. 그룹4에 묶인 진해만의 6월~11월 조사정점에서는 등가시치, 흰베도라치 등의 어류가 우점하였다. 우점종인 마루자주새우는 6월까지 포란개체가 많이 어획되었고, 등가시치와 주둥치는 조사기간 동안 대부분 소형개체가 출현하였다. 이는 본 해역이 수산생물의 산란장 및 성육장으로 중요한 역할을 함을 알 수 있다.

The main purpose of this study is to analyse economic feasibility of low-carbon-oriented trawl gear. The results of benefit/cost analysis showed that use of the low-carbon fishing gear is economically feasible. Considering the fuel saving and relatively low CO2 emission by reducing the resistance of gear, net present value by such gear improvement was estimated about 2,430~2,853 million won with the benefit-cost ratio 1.65~1.84 and the internal rate of return 29.18~30.48 percent. Development of low-carbon trawl gear would render significant contributions to reducing CO2 emission in fishing operations and lead to reduce fishing costs due to fuel savings.