In order to replace sardine baits for octopus pot, an efficacy experiment to lure with alternative bait (fermented skate or chicken skin in artificial crab or northern clam) pots and sardine pot were conducted in a circular water tank. The soaking time of the sardine bait was divided into two categories: six days or less and seven days or more. The behavioral response of octopus to the artificial bait pots and sardine pot were investigated. In the comparison of the luring effects between pots with fermented skate inside artificial crab or northern clam and sardine pot, the pot with artificial crab + fermented skate had better results than the other pots in the section distribution (31.6%) and the number of times the pot was entered into (20.0%) (p > 0.05). In the comparison of the luring effects between pots with chicken skin inside artificial crab or northern clam and sardine pot, the pot with northern clam + chicken skin had better results than the other pots in the section distribution (22.6%) and number of times the pot was entered into (55.6%) (p < 0.05). The results were also better compared to those of pot with artificial crab + fermented skate. From these results, it seems that in the luring effect aspect, sardine bait can be replaced with artificial bait consisting of chicken skin inside northern clam.

This study investigated the luring effect of the sardine bait, which is used to catch octopus with pot, as the preliminary study for the development of alternative bait for octopus pot. The soaking time for bait was divided into “5 days or less” and “11 days or longer” The number of times octopus entered the pot with bait and the empty pot was investigated under dark adaptation and light adaptation processes and the distribution of tank section was investigated under light adaptation process. The case of “11 days or longer” sardine soaking time showed higher rate of distribution in the section of pot with bait compared to the case of “5 days or less” In the case of “5 days or less” soaking time, the number of times the octopus entered the pot with bait was similar to that it entered the pot without it even during dark adaptation and light adaptation. However, in the case of “11 days or longer”, the octopus entered the pot with bait more quickly than the pot without bait and more frequently during dark adaptation hours. There were cases where the octopus did not enter any pot. In the case of “5 days or less”, with less decomposition of baits, the octopus entered the empty pot more during light adaptation process, and it appeared that the pot was used as a hideout.

In this study, we tested Japanese trolling lines in the Jeju fishery. This fishery simulates the natural marine environment with many seabed rocks, and has been redesigned and manufactured it to be suitable for the Jeju fishery. In order to ensure that the trolling lines were deployed at the inhabitation depth of hairtails, the conditions required for the fishing gear to reach the target depth were determined for use during the experiment. The experimental test fishing was conducted at the depth of 120 m water in front of Jeju Seongsanpo and in the offshore area of Jeju Hanlim. The fishing gear used in the test fishing is currently used in a variety of field operations in Japan. However, several problems were identified, such as twisting of the line during its deployment and excessive sinking of the main line. The fishing gear was, therefore, redesigned and manufactured to be more suitable for the Jeju fishery environment. For the fishing gear to accurately reach the target depth, depth loggers were installed at the starting point of the main line and at the 250 m and 340 m points of the line. Depth and time were recorded every 10 seconds. According to the daytime positioning of hairtails in the lower water column, the target depth of the fishing gear was set at 100-110 m, which was 10-20 m above the sea floor. At a speed of 1.9 knots and with a 9 kg sinker attached, the main fishing line was deployed and catch yields at depths of 100 m, 150 m and 180 m were recorded and analyzed. When the 180 m main line was fully deployed, the time for the hairtail trolling lines to arrive at the appropriate configuration had to be 5 minutes. At this time, the depth of the fishing gear was 16-23 m above the sea floor, in accordance with the depths at which the hairtails were during the day. In addition, in order to accurately place the fishing gear at the inhabitation water depth of hairtails, the experimental test fishing utilized the results of the depth testing that identified the conditions required for the fishing gear to reach the target depth, and the result was a catch of up to 97 kg a day.

The catch performance of the silver-white jig for automatic jigging machine, developed to improve the effectiveness of LED fishing lamp in catching squid, was compared to that of the conventional green jig. The vessels used in this investigation were Haesong-ho (A-vessel), a training vessel of Gangwon State University and Haengbok-ho (B-vessel), a commercial fishing boat. In the case of the A-vessel, five to eight automatic jigging machines were used in the fishing operation with a 31.3 kW LED fishing lamp in summer. As for the B-vessel, fourteen automatic jigging machines were used with a 43.2 kW LED fishing lamp in autumn and winter. The results showed that the catch performance of the silver-white jig was similar to that of the green jig in the case of the A-vessel (p>0.05). However, in the case of the B-vessel, the catch performance of the silver-white jig was superior to that of the green jig in both winter (p<0.05) and autumn (P<0.001). Based on the catch performance results regarding the B-vessel in autumn, it is expected that the annual income increase that can be earned by using the silver-white jig will be KRW 26,385,000.

To improve the efficiency of hairtail trolling, it is important to gain an accurate understanding of the distribution of fish based on their diurnal vertical migration patterns. This study evaluated the vertical distribution of hairtails through catch efficiency tests using vertical longlines. Five replicate tests of the efficiency were carried out on the eastern coast of Jeju Island from August to September 2016, from 11:00 AM to 03:00 PM in the daytime and 11:00 PM to 03:00 AM in the nighttime. The fishing gear was composed of 20 hooks per line set, numbered in order from the first hook near the surface to the last hook on the seabed. The depth of the first hook was 18 m, and that of the last hook was 86 m. Pacific saury was used as the baits. In total, 10 sets of fishing gear were used per trip. After fishing, we counted the hairtails at each numbered hook, which were summed up both by number and in aggregate. A total of 232 hairtails were caught using 2,000 hooks: 193 individuals at daytime and 39 at nighttime. The hook rate was 11.5% : 9.6% at daytime; 2.0% at nighttime. For both daytime and nighttime catches, there were variations in the hook rates at each numbered hook. In the daytime, a maximum of 28.5% catches occurred at hook number 18, followed by 21.4% at number 20, and 10.7% at number 17, accounting for 60.6% of the daytime hook rates. In the nighttime, a maximum of 23.0% catches occurred at hook number 1, followed by 15.3% at hook number 4 and 9, accounting for 53.6% of the nighttime hook rate. Based on the above results, hairtails are usually distributed in deeper region in daytime, whereas they occur near the surface in nighttime. Therefore, it is necessary to position trolling lines according to diurnal vertical distribution layers of hairtails for fishing efficiency.

This study carried out an experiment to find out the reaction of hairtail, Trichinus lepturus to the colors of LED light as a basic study on the development of the trolling gear and a method to enable the day-night operation. We used hairtails caught around Seongsan-po, Jeju Island by set nets and hairtail angling. The seven hairtails of the average length 68.9 cm (SD 9.2 cm) and the average weight 135.9 g (SD 47.9 g) were adapted themselves in the experimental water tank, 15 m Self-Governing 1.7 m in height and 1.5 m in depth, and then they were studied. We conducted experiment at the Ocean and Fisheries Research Institute in Jeju Special Self-Governing Province, from November to December 2015, and the sea surface temperature was between 16.5 and 19.5℃. The four colors of LED light, blue, white, green and red, were set up to transmit downward from the marginal area of tank. The 1 meter depth light intensity of LED colors is as follows: 0.09 w/m2/s (blue), 0.18 w/m2/s (white), 0.04 w/m2/s (green) and 0.007 w/m2/s(red) To know the optimum LED color light, we selected one with better reaction rate after comparison of two colors simultaneously and the selected color was again compared to the other color in a tournament style two times a day (day and night) and ten times totally. The reaction rates were shown as the frequencies of hairtail appearance for 5 minutes in the lighting zone after turning on the LED lights. The reaction rate of the blue was at 97% unlike the red 3% (p < 0.001). The blue was at 75% unlike the green at 25% (p < 0.001). The blue was at 67% unlike the white at 33% (p < 0.001). Therefore, the color of light source showing the highest reaction rate was the blue.

This study was conducted to investigate the fishing efficiency of an improved LED fishing lamp for squids. A total of 31 fishing operations were carried out with six-crew commercial fishing vessel Haengbok-Ho (24 tons) on which 43.2kWLED was installed, along with 14 automatic jigging machines, from October 6 to November 16, 2012. The 19 fishing vessels with Haengbok-Ho were compared with a control subject was 24 tons or 29 tons. A total illuminating power ofmetal halide (MH) fishing lamps in the control fishing vessel was either 84kW or 120kW. The number of automatic jigging machines in the control vessels was 8-18 and the number of crews engaged for fishing operation was 3-13. Average fuel consumption of LED fishing vessels during fishing operation was 505.1l which led to an average fuel consumption of 42.7l per hour. LED fishing vessel andMH fishing vessel caught on an average 1,946 squids and 2,439 squids, respectively, during the study period. Crews (hand line and hand reel) caught about 2.2 times the automatic jiggingmachines for LED fishing vessel and about 2.1 times forMH fishing vessel. Meanwhile, catches by the fishing vessels with LED in the combined total number per one line of automatic jigging machine and per crew were 86.6% of that of the control fishing vessel with MH. Also, fishing vessels with LED per automatic jigging machine achieved 71.8% of catches of that with MH fishing lamp. The catches of squids per the fishing vessel with 1W LED fishing lamp were higher by more than 135.5% of that in the fishing vessel with MH, which showed a good fishing performance even with only the use of a LED fishing lamp.

This study has conducted a comparative analysis on the fishing efficiency of LED fishing lamps by squid jigging vessels, the Yeongrak-ho (16 tons) and Somang-ho (9.77 tons), which operated during September and October 2010 and during October 2011, comparing with MH (Metal Halide) fishing lamp-equipped fishing vessels. This study has also examined vessel's fuel consumption level. The light powers of LED fishing lamps of the Yeongrak-ho and Somang-ho were 25.8kW and 32kW, respectively. Those of the MH fishing vessels, that is, the MH fishing lamp-equipped fishing vessels, were 105kW and 81kW, respectively. The average squid catch in number of an LED vessel, Yeongrak-ho, was 39.2% of the MH fishing lamp-equipped fishing vessels; however, that of the Somang-ho improved to 78.7% of the MH fishing lamp-equipped vessels. Average catch in number by Yeongrak-ho crew was 2.6 times more than catch in number by automatic jigging machines. Average catch in number by MH fishing vessel crew was 1.8 times more than that by automatic jigging machines. An LED vessel, Yeongrak-ho's fishing rate was 17.5%~152.2% of the MH fishing vessels, that is, 61.1% on average, in comparison of combined catch in number per automatic jigging machine and per crewmember. Somang-ho's fishing rate was 6.7%~127.6% of the MH fishing vessels, that is, 73.1% on average. The average fuel consumption level of the Somang-ho, throughout its departure from to arrival at the port, was 475.7l, and that during fishing hours was 109.6l, or 23.0% of the total fuel consumption level. Somang-ho's fuel consumption level per fishing hour was 9.7l on average.

Decoys for automatic jigging machines, the body part of a squid hook, have been developed in small and existing sizes in consideration of squid food, color blindness, and retinomotor responses and in utilization of pearl pigment, PP of high transparency, and combined mixture. In comparison of the developed silver-white decoy and existing decoys, the optical characteristics were examined, and the fishing performance of small size silver-white squid hooks was assessed in application of 4 fishing boats with the squid automatic jigging machine and metal halide fishing lamp in July, 2012. The luminances of the three squid hook colors-green, dark green and silver-white-increased as the intensity of illumination increased. Among these, the increase of silver-white was particularly distinguished. As to the average contrast of squid hooks, that of silver-white was 10.33, which was the highest, and then green 1.86 and dark green -0.10 in the order. As to the fishing performance of the silver-white hook, that of the 202 Geumyeong-ho and 101Yongjin-ho which caught squids were similar to that of the existing green hook and was relatively low in the case of the Dongbu-ho. However, that of the Haengbok-ho which caught relatively small squids whose average length was 19.9cm and installed silver-white hook in all automatic jigging machines was significantly excellent. In order to enhance the fishing performance of small size silver-white hooks, therefore, it would be effective to install in every automatic jigging machines of fishing boat and to start fishing before July by which small squids are caught.

This study surveyed the fishing efficiency for Japanese common squid based on improvements made to LED fishing lamps by utilizing the training ship of Gangwon Provincial College. The training ship, Haesong-ho (24 tons), was equipped with seventy-two 150W electric power LED fishing lamps (10.8kW), and their fishing efficiency and fuel consumption level were surveyed for a total of ten times during the period between June 15, 2009 and July 27, 2009. In addition, the training ship was equipped with seventy-one 300W electric power LED fishing lamps (21.3kW) and their fishing efficiency and fuel consumption level were surveyed for a total of five times during the period between January 17, 2010 and August 4, 2010. In order to compare the fishing efficiency of LED fishing lamps, the catch of another fishing vessel equipped with Metal Halide (MH) fishing lamps of 120kW for the same period and at the same fishing grounds. The fuel consumption levels during the fishing operation of Haesong-ho was about 1,047.7 liters which was approximately 19.9% of the total fuel consumption level of 5,262.6 liters, and the fuel consumption level per operation hour was on average 9.2 liters. The number of Japanese common squid caught by the LED fishing lamp-equipped fishing vessel ranged from 12 to 1,640 squid for each fishing trial and the average quantity was 652. The number of Japanese common squid caught by the MH fishing lamp-equipped 10 fishing vessels ranged from 40 to 4,800 squid and the average quantity was 2,055. The fishing of Japanese common squid was done by the use of hand lines and an automatic jigging machine. The number of Japanese common squid caught per hand line and a single roller of the automatic jigging machine was in the proportion of 50.8% to 49.2% with respect to the LED fishing lamp-equipped fishing vessel. However, the number of Japanese common squid caught per hand line and a single roller of the automatic jigging machine was in the proportion of 86.4% to 13.6% with respect to the MH fishing lamp-equipped fishing vessel where most of the catch was made by hand lines. On the other hand, in comparing the number of Japanese common squid caught per automatic jigging machine, the number of squid caught by the LED fishing lamp-equipped fishing vessel was about the same or greater than the number of squid caught by the MH fishing lamp-equipped fishing vessel.

This study made a comparative analysis of behavioral reaction of squid to red (624nm), green (524nm), blue (460nm) & white LED light, its arrival time for the shadow section by making the shadow section in the central section of a water tank just like the bottom part of a squid jigging vessel, and on-site catching efficiency of LED fishing lamp with control fishing vessel. The color LED light showing the highest squidgathering rate as against the shadow section was found to be blue LED light with 39.3% rate under the dark (0.05lx) condition. Under the brighter condition than 0.05lx, white LED light was found to have the highest gathering rate of 41.5%. In addition, it was found that squid gathering rate was high at the shadow section which showed 6.3-fold brightness difference between the shadow section and bright section. As for the arrival time for the shadow section, blue LED light was found to be the fastest in attracting squids in 192.7 seconds under the dark condition while the red LED light was the fastest in luring squids in 164.6 seconds under the bright condition. The ratio of the squid-jigging operation and sailing in fuel consumption of the fishing vessel loaded with LED fishing lamp is about 7 to 1, showing most of the fuel is consumed more in sailing than in squid-jigging operation. As for a catch of squid, the control vessel loaded with MH (Metal Halide) fishing lamp had more catch of 600-7,080 squids than the vessel loaded with LED fishing lamp having a catch of 260-1,700 squids. In addition, even in the comparison of a catch per automatic jigging machine, the catch of the vessel loaded with MH fishing lamp excelled that of the vessel loaded with LED fishing lamp in 6 operations of squid jigging out of 9 operations. The ratio of hand-jigging and automatic jigging machine (one line) in the LED fishing lamp vessel was 1:1.1 excepting the case of having a catch only using an automatic jigging machine, showing almost the same with each other in catches, while in case of a MH fishing lamp vessel, its ratio against hand-jigging was 1 to 5.8, showing hand-jigging excelled in catches.

The choice behavior of the octopus in response to the environment-friendly colored sinker for octopus driftline and the sinker's fishing effect were studied under experimental conditions in the water tank and the field. The colors of the sinkers used for the experiment are white, black, yellow and green. Artificial baits are attached to the sinkers in order to attract the octopuses in the experiment. In the water tank experiment, two sinkers of two different colors are placed in a compartmentalized corner of the rectangular tank, and a CCD camera records the choice behaviors of the octopuses to the colored sinkers. In the field experiment, the catch investigation of octopus for each colored sinker was conducted 14 times in total by using 2(A, B) commercial fishing boats at the coast of Gangneung within 30m of depth in 2006. The number of colored sinkers per operation was a total of 24-40 pieces with the same number of sinkers individually for four colors. As a result, it was found that the octopus selected white the most followed by black and yellow in their choice of colored sinkers in the water tank experiment, and green was the lowest in their choice. Even in the field experiment, the sinkers of white and black showed a higher catch of octopus than the sinkers of yellow and green.

To study the behavioral reaction of common squid Todarodes pacificus, to different colors of LED light, individual distribution in the dark condition without LED light stimuli, individual distribution when four colors of light stimuli were at the sections of end and middle of water tank and the changes of gathering rates as the elapse of illuminating time were examined. When it was dark, the distribution of the fish in each section of the tank was U-shape regardless of the investigating time intervals, which means that Todarodes pacificus gathered at the both ends of the tank. The individual distribution when light stimuli were at the one end of the tank showed the tendency of gathering at the illuminated section and decreasing at the opposite section. There were 448 of them at the end of the tank when the light was blue, 352 when white, 302 when green and 132 when red. Thus the fish liked blue light the most, followed by white light. The variations of gathering rate at the both ends of tank as illuminating time elapsed showed the tendency of increasing at the light section (A section), however, it showed the tendency of decreasing at the darkest section (F section). The individual distribution showed the tendency of letter Λ of gathering at the center and decreasing at the both ends mostly when the light stimuli were at the middle section of tank. The gathering rates at the lighting section were 80.4% when red, 76.4% when white, 69.6% when green and 56.7% when blue. The fishes showed the affinity for the red light mostly, followed by the white light source. The red light and blue light showed the opposite when the light stimuli were at the one end of water tank. The variations of gathering rates as the elapse of time at the lighted section showed the tendency of gradual increasing in the four light sources. The color of light source showing the highest gathering rate within 25-30 minutes of light stimuli was the white, followed by the red.

For environment-friendly fishery, the lead sinkers of octopus drift line were developed with the environmentfriendly sinker, and their characteristics and performance were investigated. To make the environmentfriendly sinker, the hydrate ceramic material was developed, and to increase the weight and strength, the iron power was added to it. The fishing hook was machine-made, and standardized, by using 60cm iron wire. For the manufacture of the sinker, the first, the mold was made, and then, hydrate ceramic material and water were quantitatively mixed. The mixture was poured into the mold prepared with a fishing hook already inserted, and had hardened for several hour, before it was taken out of the mold as a complete sinker. The sinkers were made in the 8 types ranging in weight from 150 to 500g, and their specific gravities were diverse from 2.871 to 6.637, which was 0.19 to 0.44 times lower than that of lead. The movement of the environment-friendly sinker by flume tank was possible in the weaker current speed than the similar lead sinker. In the coastal fishing grounds of Gangwon province, the comparison of catching efficiency was made between the improved fishing gears composed of the environment-friendly sinkers and artificial baits, and the current used fishing gears of lead sinkers and pig-fat baits. The result showed the tendency in which the improved fishing gears caught the bigger octopuses than the current used fishing gears. In the quantity and number of the fish catch per unit fishing gear, the improved fishing gear showed a little more catch than the current used fishing gear, regardless of the fishing area. However, the number of the improved fishing gears lost during fishing operation was similar to that of the current used fishing gears.

The crayfish-shaped artificial bait for octopus drift line is manufactured, into which is made to insert ordinary bait. The effects of the artificial bait are confirmed through the analysis of octopus' behavior in the laboratory in comparison with the existing bait of pig-fat skin, and the investigation of the octopus catch on the sea, and in addition, the examination of the water quality in relation to the bait to be inserted into the artificial bait is done together. The artificial bait is red in color, 10.5cm in the length of the body, and 29g in weight. The octopus behavior in relation to the bait in the laboratory has shown a good result in which more than 30% of the octopuses rushed to the artificial bait. In the analysis of the octopus sitting time by the bait, the octopus stayed longer with the artificial bait(63.7%) than the pig-fat skin(25.1%). The octopus sitting time at the artificial bait inserted with frozen squid(48.8％, 44.6％) is shown to be longer than that of the pig-fat skin(36.9％) or boiled fish paste(21.2％). In the analysis of sitting frequency to the bait, the case of the artificial bait(total 17 times) was more than that of the pig-fat skin(total 3 times), and the case of the artificial bait with frozen squid attracted the octopuses more frequently than that of the pig-fat skin or the boiled fish paste. In the field experiment, the fishing boat A(Manseon-ho, 1.22tons) caught the total 93 octopuses, while the fishing boat B(Ilho-ho, 0.73tons) caught the total 154 octopuses, all of which weighed less than 9.0kg. In the comparison with the total catch, the case with the artificial bait was a little higher than that of the pig-fat skin(**p < 0.05). In the analysis of the water quality in relation to the baits, the COD showed the descending order of frozen squid(0.57mg/g), boiled fish paste(0.18mg/g), and pig-fat skin(0.10mg/g), and the case with frozen squid was the highest and the case of the pig-fat skin, lowest. The total phosphorus, like the COD, showed the highest in frozen squid(0.02mg/g), and in case of the total nitrogen, unlike the COD, the pig-fat skin was shown to be the highest(0.006mg/g).