Hyeon-Ok Shin

Estimation of demersal fish biomass using hydroacoustic and catch data in the marine ranching area (MRA ) of Jeju

Hybrid surveys using hydroacoustic and fish sampling gears such as trammel net , trap were conducted toinvestigate total biomass , distribution and dominant fish species of the demersal fishes in the marineranching area (MRA ) of Jeju . Four surveys were carried out in June , August , October and November using38 kHz quantitative echo sounder . Catch data using trammel net and trap were used to calculate biomass andto examine dominant fish species . Fish schools were mainly detected in the waters of 20 meters below andaround Chagwido waters . By the result of fishing experiments , fish species living in MRA of Jeju wereabout 40 species , dominant fish species of a detectable fish such as Family Sparidae and FamilyMonacanthidae etc . were identified 59.4~68.8% of total biomass . Based on the hydroacoustic data , fishlength -weight function and target strength information , mean density of the demersal fish estimated were as

Simplified trawl system modeling and design of a depth control system using fuzzy logic

Abstract This paper describes a simplified mathematical model of a mid-water trawl system developed to help and understand the dynamic behavior of trawl, and to design the depth control system of the mid-water trawl operation. The equations of the motion for the vertically moved trawl system were obtained using Lagrange’s equation with respect to the variables of the displacement of the trawler, the length of the trawl warp, the angle of the warp to the horizon, and the angle of the hand rope to the horizon. These equations were modified as simplified types. A fuzzy logic controller was designed to control the depth of a mid-water trawl net. The fuzzy controller calculates the tension of the trawl warp to be changed, based on the depth error between desired depth and actual depth of the trawl net and the ratio of changes in the depth error. The error and error change are calculated every second of sampling time. The control input, i.e., the desirable tension of the trawl warp is determined by inference from the linguistic control rules, which is usually carried out by crew experienced in controlling the depth of the trawl net during manual operation. Computer simulations indicated that the calculated motion of the trawl system using the simplified mathematical model agreed reasonably with those of the original model and actual trawl system obtained from field experiments, and the proposed fuzzy controller rapidly followed the desired depth without steady-state error.

Hydro-acoustic survey on fish distribution and aggregated fish at artificial reefs in marine ranching area

Hydro-acoustic survey was carried out to estimate a fish distribution at marine ranching area and aggregated fish schools at artificial reef area in Oeyeondo, Korea. The survey system was set up with DGPS system, scientific echo sounder (EK60, Simrad Co.), and ECDIS (Mecys. Co. LTD). A track survey and a random survey was respectively applied to the marine ranching area (474.4ha) and to the artificial reef area (within a radius of 300m). As the result, fish distribution and MVBS values in marine ranching area showed that created fisheries resources didn`t come to be abundant yet as to appear fish distribution in all of the area. In the artificial reef area, it was, however, able to detect many fish school signals on the top of and around artificial reefs and to confirm the luring effect of artificial reefs.

Application of hydro-acoustic survey technique for abundance estimation of juvenile cod (Gadus macrocephalus) in Jinhae bay, Korea

Hydro-acoustic surveys with scientific echo sounder were carried out to estimate the total density and distribution of the juvenile cod in Jinhae bay, Korea. The surveys were conducted 4 times from May to June using 2 frequency method (38kHz and 120kHz) and beam trawl were used to investigate the species composition. Also the catch amounts of juvenile cod were compared with the cod density estimated by the hydro-acoustic method. It was confirmed that the juvenile cod was stayed in Jinhae bay in early June and There was the relationship between catch of juvenile cod and the estimated density by hydro-acoustic survey. The number of juvenile cod was consequently about 365,000 fish (CV 12.9%) in May and 113,000 fish (CV 9.2%) in May based on the hydro-acoustic data.

Comparison of behavior characteristics between wild and cultured black seabream Acanthopagrus schlegeli using acoustic telemetry

, one of target species topromote resource in the marine ranching area. Two wild fish and five cultured fish were released in themarine ranching area after tagging surgically. Three of cultured fish were domesticated using the remoteacoustic conditioning system for 3 weeks before being released. Two wild fish stayed at the released pointfor 2 hours and 9 days, respectively. One of wild fish was found about 10.8km away from the released pointafter 5 months. Two cultured fish stayed at the released point for 6 days and 75 days, respectively. One ofacoustic conditioned fish stayed at the released point for 131 days and then was found about 10.1km awayfrom the released point after 25 days. Others stayed at the released point during this study period(159 days).Key words : Acoustic telemetry,

Characteristics of bridge task in Korean coastal large trawler

To suggest a standard concerning with the arrangement of bridge equipment, the authors conducted the video observations with 3CCD (charge coupled device) cameras installed on the ceil of the bridge for monitoring the working activities of two bridge teams (the skipper/mate1 and the skipper/mate2) in a Korean coastal large trawler(gross tonnage: 139) for five days from July 30th. 2010 and analyzed of the data. Work elements coded by the work activities were input on the sheet of work analysis by the time unit of 1 sec according to the time occurred. A single work element among the work activities for every 5 minutes was denoted as the number of occurrence. The frequency of equipment usage was limited only in the usage of the equipment. In the case of the navigation and the towing net two ranks were integrated and analyzed. On the other hand, in the case of the casting net and the hauling net, two processes were integrated to as one and then analyzed separately as two ranks. As the results, 15 elements of work was carried out between two bridge teams for the observation; lookout, radar, GPS plotter, fish finder, net monitor, fishing deck, RPM indicator, rudder angle indicator, compass card, for maneuver; steering, ship speed control, trawl winch operation and external communications, paper works and others. It was found that the work load of the skipper per 5 minutes accordance with the navigation, the casting net, the towing net and the hauling net are 20.5 times, 11.9 times, 38.0 times and 9.5 times respectively, the mates are 65.2 times, 66.5 times, 85.7 times and 59.1 times respectively. The radar was shown the highest frequency of the equipment usage and the next was the fish finder, the GPS plotter and the external communications in the case of the navigation. In the case of the towing net the frequency of usage was high the ranking as the radar, the net monitor, the fish finder, the GPS plotter, the steering system and the external communications. In the case of the integrated process both of the casting and hauling net the trawl winch was shown the highest frequency to the skipper and the next was the GPS plotter and the radar, and the steering system was shown the highest frequency to the mate and the next was the radar, the ship speed control system, the GPS plotter, the net monitor and the fish finder.

Movement range and behavior of mandarin fish (Siniperca scherzeri) and catfish (Parasilurus asotus) in Chungju Lake

) with acoustic telemetrymethod in Chungju Lake, Korea. Mandarin fish tended to stay within 1km from the release points indownstream, and had a strong diurnal behavior. They approached to the lakefront at night. They alsopreferred to stay at deep water off the lakefront. The average swimming speed was faster at night (0.4BL/s)than during a day (0.2BL/s). They swam the shallow water area at night. Catfish frequently moved betweenupstream and downstream. Catfish tended to act during a day. The average swimming speed was fasterduring a day (0.3BL/s) than at night (0.2 BL/s). The average swimming depth was 14.3m, and they tended tofloat about 4m during a day.Keywords: Acoustic telemetry,

Variation of the Turning Circle by the Rudder Angle and the Ship's Speed-Mainly on the Training Ship KAYA-

The size of the ship`s turning circle is influenced by various factors, such as block coefficient, underwater side shape, rudder area ratio, draft, trim and Froude`s number. Most of them are already fixed on departure from a port. However, the ship`s speed and the rudder angle are controllable factors which operations are able to change optionally during sailing. The DGPS measured the turning circles according to the ship`s speed and the rudder angle. The maximum advances by slow and full ahead were 302m and 311m, and the maximum transfers were 460m and 452m, respectively. There occurs almost no difference in size of the turning circle by variation of the ship`s speeds. When the rudder angles were changed to , and , the maximum advances were 447m, 271m and 202m, and then also the maximum transfers 657m, 426m and 285m, respectively. The diameter of the tuning circle was decreased exponentially when the rudder angle was increased. The maneuverability was better when the direction of turning and propulsion of propeller are in the opposite direction rather than in the same one togetherm. The distance of the maximum transfer was always bigger than that of the maximum advance.

A study for behavior analysis of rockfish (Sebastes inermis) corresponding to the LED light by image analysis

In order to establish the basic data for the active use of the LED light source in the aquaculture industry, the experiment about the behavior of rockfish (Sebastes inermis) corresponding to the LED light was conducted by image analysis. LED lights for the experiment were one red light (wave length: 622 nm; light power: 811 mW) and two green lights (wave length: 518 nm; light power: 648 mW, wave length: 518 nm; light power: 810 mW). Behavior of the rockfish was analyzed using a moving distance (MD5) for 5 minutes where MD5s during the period of feeding were 20.0 m, 19.6 m, 16.3 m and 20.5 m in the ch1, ch2, ch3 and ch4. At the sunrise, mean MD5 of the entire channel about right before and right after were 6.3 m and 8.2 m. At the sunrise, mean MD5s of the entire channel about right before and right after were 13.6 m and 12.0 m. In the ch1, ch2 and ch3, mean MD5s during the period of 24 hours were 13.2 m, 9.6 m and 6.8 m at experiment 1and 5.2 m, 3.8 m and 2.9 m in the experiment 2.

Physical Parameter Measurement and Theoretical Target Strength Estimation of Juvenile Cod (Gadus macrocephalus)

The contrast (fish body to medium ratio) of density and sound speed were measured to estimate acoustic scattering from small juvenile cod (Gadus macrocephalus) with the Kirchhoff-Ray Mode backscatter model. The density contrast was measured by the density-bottle method and the sound speed contrast was estimated by the time of flight method. The results revealed that the measured density contrasts of juvenile cod varied between 1.003 and 1.029 (mean = 1.014, S.D. = 0.01). On the other hand, sound speed contrasts varied between 1.039 and 1.041 (mean = 1.041, S.D. = 0.001). The relationship between averaged target strength (TS) and total length (TL) established by the model were 38kHz > = 20log(TL) . 68.8 and 120kHz > = 20log(TL) . 69.4, respectively.