For the optimal design of a shrimp pot to control the catch size and to reduce catch the small size shrimp, tank experiments were carried out to study the pot stability under water. Tank experiments were carried out to measure the drag with 4 kinds of model pots that have 50% selection on the individual of 25mm carapace length. The drag of each pot was measured every 10 times with changing the current speeds from 0.1m/s to 0.7m/s in 0.1m/s intervals and the pot attack angle from 0˚ to 90˚ in 15˚ interval in a flume tank. The relation between the current speed and drag was presented. The stability of pot was estimated using the drag data and the friction data of Kim et al. (2008b). The results showed that, the drag was shown lower as small as the projected area of pot depending on the current speeds and angles. The model pots were showed to slide on the seabed in case of rock at the current speeds 0.35-0.38m/s and the possibility of turn over at the current speeds 0.77-0.89m/s. In conclusion, the stability of a shrimp pot showed more stable as the pot of the lower the height and the smaller projected area on current.

In an attempt to respond to the increase in international oil prices and reduce operating expenses, ship remodeling was carried out on a 740ton class tuna purse seiner. To strengthen the competitiveness of the fisheries industry by improving vessel performance, a bulbous bow was newly equipped. The slipway and rudder area were also lengthened and enlarged with the propeller and main engine remained unchanged. To reduce the hull resistance, a circle type bulbous bow was attached on the hull behind bow thruster and thus the cost for exchanging electrical equipment for bow thruster was reduced. The new rudder area was expanded 15% more than the old one within the extent that the existing mechanical control part and rudder stock were not changed. To prevent fishing net damage and stabilize wake field, slipway was lengthened to the optimal position. All of the new design of remodeling parts went through the model tests in towing tank and CWC. Besides resistance test, all of necessary model test results were delivered for hydrodynamic character for the modified ship. The maneuvering simulation to verify that the remodeled ship satisfies the IMO rules was performed in both zigzag and turning tests. The estimated resistance with new bulbous bow and lengthened stern was reduced by 4.8% in the 2-dimensional analysis and 17.4% in the 3-dimensional analysis in comparison of conventional ship. The average reduction of resistance was estimated about 10%. Maneuvering character of modified hull form was found to satisfy all regulations under IMO. The remodeling of tuna purse seiner can not only improve fishing performance but also contribute to reduction of operating cost by saving energy for the fisheries industry.

To establish a vessel safety management system for improving the safety of vessel's traffic and preventing vessel's traffic accidents, the state of marine traffic in the Busan South Port was investigated and analyzed as preliminary survey of the countermeasures. As a result of the study, there are 1,158 vessels in a day, 48 vessels in an hour, and the maximum traffic is about 118 vessels between 16:00 and 17:00 hours everyday, which requires to establish and operate a traffic control system necessarily for ensuring vessel's traffic safety. Furthermore, passages of tanker, passenger ship, cargo vessel and government vessel showed to sail along main traffic lane to be obtained enough sea depth at the survey area. However, passages of fishing vessel and launch showed to sail freely at all survey area owing to outstanding maneuverability and a shallow draft. Some vessels of launch sailed along main traffic lane, but other vessels crossed to sail it. The passages to cross main traffic lane is higher the risk of collision. Therefore, safety measures are urgently needed for the operation of the Busan South Port management system and the prevention of marine pollution.

Simulation technique for the fish behavior was applied to estimate fish school movement in the cage net. Individual-based fish behavior model (Huth and Wessel, 1991) was evaluated in a free area to understand the characteristics for the model, and the movement in the cage net was simulated by defining the fish reaction against the displacement of cage net. As a result, the distance to the net was not considerably changed and the space among fishes in cage net was slightly decreased by reducing the net space. Swimming area was, however, significantly affected by changing the net space and the relationship between swimming area and net displacement was theoretically estimated as y=-0.21x+1.02 (R2=0.96). these results leads the conclusion that individual-based model was appropriated to describe the fish school reaction in the cage net and be able to use for evaluating the influence on cultured fish.

As a fish way is a structure for fish migrating well toward upper stream due to breaking river flow by a dam or dammed pool, the specific fish's swimming ability is one of the main factors in making a plan and managing it. In addition, it also needs to understand the current field in fish road to evaluate its performance. This study is aimed to analyze the swimming patterns with current velocity changes using a Particle Imaging Velocimetry (PIV) in order to understand the swimming ability of silver fish (Plecoglossus altivelis) that is one of the fishes migrating through the fish way of Nakdong River, and to analyze the 2 dimensional current field near to silver fish at swimming momentum. The results showed that average values of tail beat frequencies for continuous swimming with current velocity were 2.8 Hz at 0.3 m/s, 3.2 Hz at 0.4 m/s, 3.8 Hz at 0.5 m/s, respectively. The wake would be produced by direction turning of fish's tail fin and its magnitude would be verified by the difference of pressure. The pressure turbulent flow produced by its tail beat would be made in both sides, and then, the magnitude of wake should be the source of moving direction. The swimming momentum will help to support the primary factor in making a suitable design for specific fish species migrating toward the district river.

Catches, CPUE, fishing season, disc width composition and fishing ground were studied to rebuild skate ray, Raja pulchra resource by the offshore longline fishery in Heuksan-do, Korea. Annual catches and CPUE of skate ray were increased from 2003 to 2010 (CPUE: from 2007 to 2010) continuously. The main fishing season of the skate ray was from December to next May. Disc width at 50% maturity for Raja pulchra by sex were estimated to be 65.83cm, 57.01cm by female and male respectively. The range of disc width was 22.3-112.0cm and the average disc width was 66.9cm, 60.0cm by female and male of Raja pulchra respectively during 2007-2010. Annual average of disc width of female skate ray was decreased from 2007 to 2010. The fishing grounds were formed from the coastal water off Hong-do to the coastal water off Gyeogyeolbiyeol-do, Korea. The center of fishing ground in October was formed in the northwestern coastal water off Gyeogyeolbiyeol-do and separated from that of the other months.

A preliminary study on species composition of a Korean purse seine catch landed at cannery was conducted in April 2011. In the cannery, all tuna catch are sliding through a sorting grid panel that filters and drops fish in the buckets by size class (above 9kg, 3.4-9kg, 1.8-3.4kg, 1.4-1.8kg and below 1.4kg). In cannery processing, species sorting was made for skipjack tuna and yellowfin tuna only from catches greater than 3.4kg during filtering but not for bigeye tuna because of difficulties in species identification between bigeye tuna and yellowfin tuna under frozen state. As no species identification was carried out for catch groups less than 3.4kg in the cannery process, this study focused on sorting out skipjack tuna and yellowfin tuna from these groups and then identifying bigeye tuna from all size groups of yellowfin tuna. Using the mixture rate of species obtained from the samples taken, species composition of the landed catch was estimated. As results, cannery research showed 95% for skipjack tuna, 3% for yellowfin tuna and 2% for bigeye tuna in species composition, while vessel logbook data represented 96%, 3% and 1% for skipjack tuna, yellowfin tuna and bigeye tuna, respectively. The proportion of bigeye tuna identified in the cannery was slightly higher than shown in logbook data by 1%.

Changes in ecosystem risks were evaluated using the ecosystem-based fisheries assessment (EBFA) approach of Zhang et al. (2009, 2010) and the comprehensive ecosystem-based fisheries management (EBFM) plan was made for the southern sea of Korea in this study. The risk assessment of the southern sea ecosystem was conducted by establishing ecosystem management objectives and by estimating risk scores (RS) for indicators. To conduct this analysis a number of indicators and their reference points for assessing these risk scores were developed in this study. The number of indicators in the risk analysis was 28 for the quantitative tier 1 analysis and 30 for the qualitative tier 2 analysis. The objective risk index (ORI), species risk index (SRI) and fisheries risk index (FRI) were calculated from the risk scores. Comparing the past (1988) and the current (2008) status of fisheries resources, management implications were discussed. The fishery risk index (FRI) of large purse seine fishery in the southern sea of Korea decreased substantially from 0.972 in 1988 to 0.883 in 2008, and improvement in the management of fisheries operated in the southern sea of Korea.

Species composition of fishes and the recruitment properties of jack mackerel, Trachurus japonicus, in the waters around the Geumo Islands in the mid-South Sea were investigated by using both sides fyke nets every month from February to December 2010. During study period, a total of 30,503 fishes (1,380.4 kg) were collected and classified into 2 classes, 16 orders, 61 families and 121 species. The dominant species was jack mackerel occupying 80.5% of total individuals and 44.4% of total biomass. The fork length range of jack mackerel was 5.5-26.8 cm and individuals about 6 cm was appeared only in the middle and southern area of the Geumo Islands in May. The new recruitment of jack mackerel appeared from May in the waters around the Geumo Islands is probably caused by the warm water intrusion associated with the development of stratification due to the extinction of seasonal coastal cold waters by the increase of solar radiation heat. Furthermore, the jack mackerels less than 6 cm recruiting in the mid-South Sea in spring were considered as mixed ones by individuals spawned in the East China Sea and in the waters around the Jeju Island considering the collected time, migration period and spawning time of them.

We conducted experiments to compare the catch rate of bigeye tuna and yellowfin tuna between circle hooks and straight shank hook in the Korean tuna longline fishery at the eastern and central Pacific Ocean from 2005 to 2007. We analyzed difference of fork length, survival and hooking location between a circle hook and a straight shank hook for both tunas, respectively. There was no difference in the mean fork length size of yellowfin tuna caught on the two type of hook but bigeye tuna was significant. In case of survival, there was no difference between two hook type, but the difference of hooking location was significant for both species. We also analyzed to find determinants of both tunas catch rate using generalized linear models (GLMs) which were used latitude, longitude, year, month, depth, hook type, bait type and so on as independent variables. Spatial factors, latitude and longitude, and temporal factors, year and month, affected catch rate of bigeye tuna and yellowfin tuna. And also, depth such as a marine environment factor was influenced on catch rate.

To obtain the effective sampling estuarine fauna by a passive net in the West Sea of Korea occurring strong tide, catch were collected by bag nets with various sampling trials off Ganghwa Island in November 2009. We compared the difference of community structures (on spring tide vs. neap tide, total sample vs. subsample and 4 nets vs. 1 net) with each species composition as a sampling unit by the Pearson chi-square test. Number of individual at the spring tide was more abundant than that at the neap tide (p<0.0001) although number of species at the spring tide was not significantly different with that at the neap tide (p=0.174). Both number of species (p=0.138) and number of individual (p=0.096) were not significantly different between total sample and random subsample. Number of species was not significantly different between the subsample by 1 net and the subsample by 4 nets (p=0.515), but number of individual was a little different on both samples (p=0.024). In conclusion, we suggest the subsample by 1 net at spring tide as the effective sampling estuarine fauna by a passive net in the West Sea occurring strong tide.

This study was conducted to develop energy-efficient LED lamps with an excellent fishing performance for an anchovy scoop net by comparing the functions of 6 different lamps- incandescent, blue LED, green LED, white LED, yellow LED and red LED lamp. We used incandescent and red LED lamps only for the initial test and then excluded because those showed the lowest herding capacity. According to the result, yellow LED showed lower herding capacity in comparison with the blue, green and white one. Although the herding performance of the blue, green and white LED was similar in almost tests, herding speed to the each light was different. The anchovies were gathered into the blue LED as the speed of 39.88cm/s that was the fastest. Green LED was the second as the speed of 33.28cm/s. White LED was the slowest as the speed of 26.73cm/s. We will have field tests because we found the result that yellow LED's herding performance was better than green LED's for 5 seconds comparing after starting in some tests.

In this study, the entrapped number is investigated on the UV light with different illuminance to fluorescent bait cage for swimming crab in order to find the appropriate illuminance which has the best attraction effect of fluorescent bait cage for pots. In addition, preference to the light, arrival time and residence time at light area are compared and analyzed to fluorescent bait cage and non-fluorescent bait cage for American lobster at the UV light and ordinary light according to the illuminance condition. Pot with red non-fluorescent bait cage at the no lighting (<0.01lux), pot with blue fluorescent bait cage at the 20W UV lighting (0.16lux) and pot with blue fluorescent bait cage at the 30W UV lighting (0.22lux) were soaked for 6 hours and the entrapped number of swimming crab was examined. The mean entrapped number of swimming crab in pot with red non-fluorescent bait cage at the no lighting (<0.01lux) was 1.0, but the mean entrapped number of swimming crab in pot with blue fluorescent bait cages at the 20W UV lighting (0.16lux) and 30W UV lighting (0.22lux) were 1.4 and 0.4, respectively (P<0.05). The rate of preference to the blue fluorescent bait cage at the UV lighting shows 1.6-4.8 times higher than that of preference to the red non-fluorescent bait cage at the ordinary lighting. In addition, The rate of preference to the blue fluorescent bait cage at the UV lighting is higher when the illuminance of ordinary light is same as or is lower than that of UV light (P<0.05). However, the preference to the light depending on gender shows no significant difference (P>0.05). The arrival time to UV light area of lobster is shown as 1.2-2.4 times faster than that to ordinary light area. Generally, it is shown that arrival time to UV light area is faster than the arrival time to ordinary light area when the illuminance of ordinary light is the same as or lower than that of UV light (P<0.05). However, arrival time to the light area depending on gender shows no significant difference (P>0.05). The residence time at UV light area of lobster is 1.2-1.7 times longer than that at ordinary light area. The residence time depending on different illuminance of ordinary light and genders showed no significant difference (P>0.05).

The investigation for the catch and species composition in the deep sea of the East Sea was done to search marine organisms using some kinds of traps with small commercial fishing vessel near Goseong, Korea from 2008 to 2009. The experiments was carried out with some different traps at the depth of 200m, 400m, 700m and 1,000m. In 2008, the amount of catch with rectangular, cone and drum net traps was 91.4kg with twelve trips and the proportion of catch with rectangular and cone traps was high. Dominant species caught were Aniwan whelk (57%), snow crab (12%), hunchback sculpin (7%) and red snow crab (5%). The catch of Aniwan whelk was done well with rectangular and cone traps at the depth of 700-1,000m. Snow crab was mainly caught with rectangular and cone traps at the shallower depth of 200m, while red snow crab caught a lot with cone trap at the deeper depth of 700m. In 2009, the amount of catch with rectangular, cone and round traps was 92.4kg with nine trips. The proportion of catch with round trap was higher than that with cone trap. Dominant species caught were snow crab (67.1%), Aniwan whelk (14.8%) and northern shrimp (9.8%). Snow crab was caught well with round trap at the depth less than 400m.

Field tests were carried out with five different mesh sizes (86.6, 101.0, 121.2, 137.7, 151.5mm) to study the relative efficiency of monofilament and multifilament gill net for Marbled sole, Pleuronectes yokohamae, in the western sea of Korea, 2007-2009. The relative efficiency was analyzed by length distribution, catch in number, catch in weight and weight per individual for Marbled sole. Statistical T-test was done to verify the efficiency between two gears. In the field tests, the total body length range, catch in number and weight of Marbled sole was 15.8-48.2cm, 728 and 254,939g, respectively. During the field tests, Marbled sole less than 15cm length which is prohibition size of fishing was not caught, but the caught number of Marbled sole less than 19.5cm length which is first maturity length was 13 (1.8%) and the caught number of Marbled sole more than 19.5cm was 715 (98.2%). Catches of monofilament gill net was average 1.4 times more efficient than multifilament gill net. The weight per individual and total length by mesh sizes in the two gears tended to gradually increase according to mesh size increasing. But there was little difference of weight per individual and total length by mesh sizes between two gears.

The purpose of this study is to identify the flow resistance of the bottom trawl net. The bottom trawl net being used in the training ship of Chonnam National University was selected as a full-scale net, and model nets such as 1/10, 1/25 and 1/50 of the actual net were made. Total resistance of the net part, the height of the net mouth and the flow resistance of components of the net such as wing, bag and cod-end part was measured, converted into full-scale and compared. Additionally, the model rule of Tauti (1934), which has been most frequently used in fishing net modeling experiments, was applied to interpret flow resistance and scale effect of model experiment was investigated. Presumed that the flow resistance R is R=kSr2 against the flow velocity of each net r, resistance coefficient k was calculated by substituting R, r and S of the net. From the result, it was found that k decreases exponentially when u increases which makes k=cr-m. Whereas m of each net is ranged between 0.13-0.16 and there was not significant difference between nets. c does not show big difference in 1/10 and 1/25 model and the value itself was relatively bigger than in 1/50 model. The height of the net mouth of 1/25 and 1/50 model net h decreases exponentially according as r increases to make h=dr-n. Whereas d and n values were almost same in two nets. Additionally, when resistance of cod-end, wing and bag part in 1/25 and 1/50 model nets, both nets showed big resistance in bag part when flow is 1m/s as more than 60%. Wing and cod-end part showed almost same value or wing part had little bit larger value. On the other hand, when reviewing the reasons why both models showed difference in 1/50 model while c value against the resistance coefficient k did not show big difference in 1/10 and 1/25 model, it is inferred that the difference occurred not from material difference but from the difference in net size according to scale. It was judged that they are the scale effects concomitant to the model experiments.

The behavior of abrasive wear on counterpart roughness of glass fiber reinforcement polyurethane resin (GF/PUR) composites were investigated at ambient temperature by pin-on-disc friction test. The friction coefficient, cumulative wear volume and surface roughness of these materials against SiC abrasive paper were determined experimentally. The major failure mechanisms were lapping layers, ploughing, delamination, deformation of resin and cracking by scanning electric microscopy (SEM) photograph of the tested surface. As increasing the counterpart roughness the GF/PUR composites indicated higher friction coefficient. The surface roughness of the GF/PUR composites was increased as the sliding velocity was higher and the counterpart roughness was rougher in wear test.

Recently, the manufacturers of life-jacket are very interested in the acquisition of USCG(US Coast Guard) approval because the acquisition of USCG approval has an important role in the purchasing decision of the buyer's. Be based on criterion of USCG, we studied how to predict the change of floating position of human model with life-jacket to verify the backside restore. For this, in this study, the human model and the lifejacket was modeled in three dimension, the application program for prediction of floating position was developed, and plugged-in commercial program.

The inherent efficiency of a ship would be prior to any other quality factors in ship's safety, because lack of it may give rise to a serious sea casuality even if it were a light mistake in operation. And the representative casualty comes from a deficiency of stability and an operating error combined would be capsizing. The Korean offshore large purseiner looks to have a structural weak point with small range of stability in spite of her big initial metacentric height, and have various type of roll reduction devices in order to cover up the defect. The aim of this study is to grasp for the roll reduction characteristics of the purseiner with bilge keel only and a stern keel additionally attached. The results are summarized as follows; The rolling angle of the model ship was increased in accordance with increase of the wave period and height, especially at close to the natural wave period of her, and the trends were more distinguished in the situation of bilge keel only installation than in the stern keel additionally installed. And stern keel has not noticeable effect on the reduction of the roll in the light ship condition, but has a little effect in full load condition.

Marine casualties of vessel are said to be in most case caused by human error, but it would be valid for the assumption that the ship is built with high quality and then should be acceptable to the safety standards. It means that the inherent characteristics of a ship should be the first consideration on the safety of ship. Therefore it is basically necessary for navigator to grasp the inherent stability of his ship and ensure that the ship complies with the minimum statutory standards of stability. This study is to realize the stability of the Korean offshore large purseiner varying with loading conditions by the inclining data and some calculations. The author compared the stability of the ship with IMO criteria and domestic rule, and proposed some improvement for the safety of the ship. The results are summarized as follows ; The values of GM of the ship according to the loading condition in navigation satisfy both of the IMO criteria and the domestic rule, but in case of the area under the GZ curves between the heel angles of 30˚ and 40˚, and the heel angle occuring the maximum righting lever not satisfy the IMO rule at the fishing ground departure and arrival conditions in the haul in net situation. The initial metacentric height of the ship is very large, but the range of stability and the occurring angle of the maximum GZ are very small, so even small inclining can bring about the beam end. The best method of improvement for that is to increase the freeboard of the model among the variables.