Biodegradable polybutylene succinate(PBS) is an environment friendly plastics for fisheries, because it can mitigate the ghost fishing problem caused by gill-net and trap fisheries. To evaluate photodegradability of PBS monofilament in comparison with polyamide(PA) and polyethylene(PE) monofilament, these 3 types of monofilaments were spun and exposed to ultraviolet light(UV) of weather-ometer for 900 hours, and then their modification, crystal structure, strength, and extensibility were analysed. PBS monofilament did not show any crack and maintained its crystal structure after 900 hour exposure to UV whereas PE monofilament began showing cracks and structure modification after 600 hour exposure. Under UV exposure, the strength and extensibility decreased more rapidly in PBS than in PA and PE. We estimate that gill nets made of PBS monofilament can endure for about 1 year. The breaking strength and elongation decreased linearly with the exposure time for the 3 types of monofilaments. The derived regression equations of the residual tenacity(RT, kg/mm2) and the residual extensibility(RE, %) with the exposure time in year(Y) for each monofilament were; PBS : RT=48.598 - 8.6437Y(R2=0.93), RE=28.165 - 7.3233Y(R2=0.98), P A : RT=59.771 - 8.6437Y(R2=0.98), RE=32.198 - 5.2772Y(R2=0.92), P E : RT=60.898 - 5.6528Y(R2=0.98), RE=11.887 - 0.7188Y(R2=0.98).
In this study, the effect of slope length and angle at the entrance to fishing pots on the size of captured shrimp was examined to determine the optimal design of pots for use in Hokkaido, Japan. The purpose of the current study was to optimize the design of shrimp pots to allow greater control over the size of captured individuals for the purposes of shrimp resource management. Tank experiments were conducted to determine the optimal slope length and slope angle by analyzing the sizes of shrimp entering 10 model pots with combinations of five different slope lengths on slope angle of current shrimp pot, and five different angles on slope length of current shrimp pot. The results showed that, as the slope length of the pot increased, the size of individuals which entered the pot increased. In addition, as the slope angle was elevated in each of the five different slope angle treatments, the size of individuals entering was also increased.
In order to develop the substitutive materials for natural baits of swimming crab pots, the attracting effects of swimming crab such as the preference of baits which were made of the by-products of marine and stock raising through the water tank experiments and fishing experiments. On the investigation of mean entrapped catch number to the pot by the baits after putting the 4 kinds of baits, mackerel(M), mackerel with grinded mackerel s internals(MMI), mackerel with tuna s internalsMMI) and makerel with grinded krill(MK) each in one pot by turns, MMI and MK were entrapped mean 3.9(13.0%) and they were a little more comparing to M, and MTI is least with mean 2.1(7.0%)(F=12.913, P 〈 0.05). Otherwise, on the preference investigation of swimming crabs by the baits after putting the 4 kinds of baits in the 4 pots each, M was entrapped mean 3.0(10%), but MMI, MTI and MK were mean 1.2(4.0%), 1.0(3.3%) and 1.5(5.0%) each and they were only 30-50% of M(F=13.398, P 〈 0.05). On the preference investigation of swimming crabs by the 5 kinds of baits, mackerel(M), and krill(K), manila clam(MC), pig s fat(PF) and chicken s head(CH) which were used in substitutive baits, M was entrapped mean 3.2(10.7%), but K was about 50% of catch of M with mean 1.6(5.3%), and MC, PF and CH were very few with mean 0.1-0.2(0.3-0.7%)(F=89.186, P 〈 0.05). On the preference investigation of swimming crabs by the pots which were put each the 3 kinds of baits, original krill(K), grinded krill with gluten and soybean oil cake(KGGS) and grinded krill with gluten, soybean oil cake and glycine(KGGSGL) in the blue fluorescent hexahedral plastic bait cages(BF), and which were put the mackerel(M) in the non-fluorescent hexahedral red plastic bait cage(RFN), it was entrapped mean 3.0(10.0%) in the pot which was put the mackerel in the RFN, and the same level in the pots which were put the K and KGGSGL in the BF, but it was mean 2.0(6.7%) in the pots which was put the KGGS in BF and it was decreased by 30% of catch comparing to RFN(F=3.750, P 〈 0.05). On the preference investigation of swimming crab by the pots which was put grinded tuna with gluten, soybean oil cake and glycine(TIGSGL) in the blue fluorescent hexahedral plastic bait cage(BF), and which was put mackerel(M) in the nonfluorescent hexahedral red plastic bait cage(RFN), it was entrapped mean 3.3(11.0%) in the pot which was put mackerel in RFN, and mean 2.7(9.0%) in the pot which was put TIGSGL in BF and it was about 15% less comparing to use bait M(t=1.387, P 〈 0.05). As a results of fishing experiments, a plan for enhancing catching efficiency of TIGSGL will be required because catching efficiency of TIGSGL, alternative bait, was half of fish catching efficiency of natural bait using mackerel. Fishing experiments were conducted 3 times using reinforced substitutive artificial bait that is reinforced attractive effect of TIGSGL and composed of tuna intestine, grinded mackerel, gluten, soybean cake, glycine and alanine(TIMGGSGLA). Catching efficiency of TIMGGSGLA was about 80% of that of natural bait made of mackerel.
Squid jigging fishery is very important in that there are about 1,000 jigging vessels more than 10 tonnage and about 5,000 ones less than 10 tonnage in Korea. But the cost of oil which is used to light fishing lamps, goes significantly up to almost one hundred million won for 50 tonnage vessels and forty million won in case of vessels less than 10 tonnage. This cost has almost taken 40% of total fishing costs. That is, the fishing business condition of squid jigging fishery is recently in the very difficult situation. As oil price increases, the business condition of the fishery gets worse and worse. Therefore it is very urgent to develop an economical fishing lamp, to solve this problem of fishery's business difficulty. This research aims at developing a fishing lamp for squid jigging fishery using the light emitting diode which has very excellent efficiency and durability. We made a water tank with 20 meters width which is a shape of raceway to research behavioral characteristics of Japanese flying squid to LED light, and made an experiment to investigate optimum wave of LED light to lure squid. The method is to establish LED lamps on both ends of water tank and to observe squid's behavior. Colors and wave lengths of LED lamps, used in experiment, are red(634nm), yellow(596nm), green(523nm), blue(454nm) and white(454nm+560nm). In experiment for attractive capability of LED lamp to squids, Japanese flying squid are highly attracted to blue lamp and white lamp. However, they are dispersed to red and yellow lamps. In addition, Japanese flying squid have moved and stayed in both dark ends of water tank. When compared intermittent lamp with continuous lamp, Japanese flying squid are highly attracted to intermittent lamp when intermittent interval is 0.25 second.
Patagonian toothfish(Dissostichus eleginoides) was investigated in the southeastern Atlantic Ocean during the period of 19 March to 7 July 2007 by commercial bottom longliners. The number of 116 hauls were carried out individually in this study area by two bottom longliners during 111 days. The total catches were 89,559kg(9.91kg/100hooks) and 66,758kg(7.38kg/100hooks), respectively. Most Patagonian toothfishes were caught on the 46-48˚S, 6-11˚E of southeastern Atlantic Ocean. Patagonian toothfish comprised 67.01-92.49%(by weight) of the catches in the southeastern Atlantic Ocean. No Antarctic toothfish (Dissostichus mawsoni) was caught during the surveys. Patagonian toothfish was found throughout the experimental area, but the density was considerably greater in the layer of 1,300-1,900m, where 49.88% of the fishes were caught. Smaller fishes were generally distributed to the shallow waters and larger fish were more frequently caught with the depth. Mean size of Patagonian toothfish increased with depth of capture. Accordingly economically profitable fishing activities for the Patagonian toothfish fishery requires an understanding of the size distribution of the Patagonian toothfish by depth.
The age and growth of the sandfish, Arctoscopus japonicus were investigated from samples of the eastern sea danish seine and gill net fishery in the East Sea of Korea from February, 2004 to December, 2007. Ages were determined from annuli in otoliths and annuli were formed between December and February once a year. Also, the main spawning period was estimated to be between December and January, thus rings were considered to be annual marks. For the relationship between fork length and total weight, a multiplicative error structure was assumed because variability in growth increased as a function of the length. The relationship between fork length and total weight were TW=0.0083FL3.01(R2=0.966) for female and TW=0.0079FL3.04(R2=0.969) for male. The variability in growth was constant as a function of age, revealing an additive error structure. The von Bertalanffy growth parameters estimated by a non-linear method were L∞=31.6cm, K=0.266/year, t0=-0.835 years for female and L∞=27.7cm, K=0.273/year, t0=-0.806 years for male. Growth at age between male and female had a significant difference(P〈0.001).
To examine species composition, abundance and biomass of demersal organisms in the East Sea, bottom trawl survey was conducted at 7 sea areas from 2005 to 2007. A total of 107 species were collected and were composed of 54 fish species, 16 crustacea, and 37 mollusks in the East Sea from 2005 to 2007. Yearly abundance per area which caught by trawl survey in the East Sea from 2005 to 2007 ranged from a high of 292,234inds./km2 in 2005 to a low of 192,092inds./km2 in 2006. The abundance by sea area showed a peak in 76 sea area, and the lowest in 63 sea area. The abundance per area by season showed a peak in summer, and the lowest in spring. The most dominant species in abundance were Clupea pallasii, Neocrangon communis, Chionoecetes opilio. Yearly biomass per area which caught by trawl survey in the East Sea from 2005 to 2007 ranged from a high of 10,322kg/km2 in 2006 to a low of 7,096kg/km2 in 2005. The most dominant species in biomass were Chionoecetes opilio, Clupea pallasii, Dasycottus setiger. The biomass by sea area also showed a peak in 76 sea area, and the lowest in 93 sea area. The abundance by season also showed a peak in summer, and the lowest in spring. As a result of cluster analysis, demersal organisms community of 76 sea area showed a large difference with other sea area, and that of summer showed a large difference with other season.
A self-regulatory community fisheries management program in Korea is designed to enhance fisheries resources, to protect fishing grounds of self-regulatory communities, and to manage their fisheries resources by their own regulations and knowledge. This study explored an applicable ecosystem-based management plan based on the scientific investigation and analysis. This study suggested objectives, indicators and reference points of the ecosystem-based resource management system which are applicable to selfregulatory community fisheries. The objectives of the management system are to maintain sustainable fisheries production, to maintain optimum fishing intensity, to reduce by-catch, to conserve spawning ground and habitat, to maintain optimum habitat environment, to increase/maintain abundance of prey species, to increase/maintain stock biomass, and to conduct stock enhancement on the basis of scientific assessment. The improved methods for the assessment and management are introduced by demonstrating a self-regulatory fishery which targets on hen clam in Dong-li fishing village in Busan.
Recently a modern style sailing boat suitable for Korean sea was designed through full three dimensional design skill by the authors. In this paper, based on this three dimensional hull and deck design, a production process of 31ft class cruiser sailing boat was developed. First of all, it was possible to make the digital mock-up for design boat. Through this mock-up and RP(rapid prototyping) modeling, an appropriate general arrangement of design boat was able to be determined at final. And also the female deck mould was able to be made by a 5-axis NC cutting machine. By doing this method, more higher efficiency and precision for sailing boat production could be achieved than before. Through this research the total process of design and construction for the designed boat was established.
The snow melting system by electric heating wires which is adopted in this research is a part of road facilities to keep surface temperature of the road higher than freezing point of water for melting the snow accumulated on it. The electric heating wires are buried under paved road at a certain depth and operated automatically and manually. Design theory, amount of heating, and installation standard vary according to economic situation, weather condition, installation place and each country applying the system. A main purpose of this study is figuring out the appropriate range of required heat capacity and installation depth and pitch for solving snowdrifts and freezing problems with minimum electric power consumption. This study was performed under the ambient air temperature(-2℃, -5℃), the pitches of the electric heating wires(200 mm, 300 mm), heating value(250 W/m2, 300 W/m2, 350 W/m2).