• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.5
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• pp.595-602
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• 2017

In Korea, much research and development have occurred to enhance the technological competitiveness of tuna purse seining fisheries. Due to these efforts, fishing efficiency has been improved with the development of radar, sonar and global positioning systems for fish detection and revisions to the hull forms of tuna purse seiners. However, for skiff boats, net boats and speed boats, which are auxiliary working boats mounted on tuna purse seiners, technology has lagged behind relative to the modernization of the main vessel. In this study, the hull of an existing propeller-based net boat with steel wire net to protect tuna was changed to the hull of a water jet propulsion vehicle to reduce resistance and improve maneuverability. As a result, a prototype of a water jet propulsion option was produced according to the aluminum structure strength standards specified by the Ministry of Oceans and Fisheries, and safety was confirmed by performing a drop test. Moreover, through a sea trial test, an existing net boat was shown to have a speed of 12.0knots and a towing force of 2,545 kgf at 2,500 RPM. The prototype had a speed of 26.7 knots and a towing force of 2,011 kgf at 3,200 RPM, which satisfied the towing capacity standards of auxiliary working boats mounted on tuna purse seiners.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.23 no.4
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• pp.177-183
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• 1987

The catch by the set net fishery from 1971 to 1985 were analyzed in order to reveal its fluctuation characteristics. Generally, the catch increased from 16,787M/T in 1971 to 84,103M/T in 1985 and showed maximum in 1979 with 99,475M/T of catch. This trend was mainly related to the higher production of file fish which accounts for 64% of the total catch in 1979, and the change of catch statistical classification according to the revising of fishery law in 1976. It was also closely related to the variation of the sea water temperature in coastal area. The main fishing period of the set net fishery appeared from October to November. Catch of the set net fishery was led by that in the southern coast before 1976 and by that in the eastern coast from 1977 to 1980, the tendency changed irregular from 1981. Three groups of fishes could be distinguished by principal component analysis of the annual catch. A group showing steady decreasing tendency was composed of the fishes such as whiting, sand fish, hair tail and anchovy. The another group composed of small alaska pollack, round herring, goby, gizzard shad, sand lance and file fish revaled an increasing tendency. The other fishes did not show any annual tendency.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.18 no.6
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• pp.571-580
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• 1985

Based on the data collected by R/V "Shinkai Maru" of the Japan Marine Fishery Resources Research Center during the period from April 1978 to April 1979, seasonal migration of Merluccius hubbsi was studied using the catch per fishing effort (tons/30 min. haul) and gonad maturity index (gonad weight /body weight X $10^3$). Merlurccius hubbsi are found in the area between $36^{\circ}S\;and\;54^{\circ}S$ along the coast of Arzentine and are abundant especially above the 100 fathoms in northern offshore of $48^{\circ}S$. It was observed that critical maturity body lengths (spawning minimum body length) in terms of gonad maturity index are 40 cm and 30cm in female and male respectively, while spawning seasons are from December to January and from November to December for female and male respectively. It was assumed that while the group which distrbutes in the north ($36^{\circ}S{\sim}39^{\circ}S$) in spring moves down south to $42^{\circ}{\sim}46^{\circ}S$ for spawning in summer (from December to January), the group which does not move or a part of this group which comes back to the north spawn in the area north of $42^{\circ}S$ throughout the long period except winter time (from July to August). Southern group as well might move north and spawn after mixing together with northern group at $42^{\circ}{\sim}46^{\circ}S$ area around the period of December to January,

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.36 no.4
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• pp.281-286
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• 2000

To analyze the shape of the net mouth of bottom trawl which is composed with 6 seams net, the field experiment was carried out on the sea near Kokunsan Is, Western sea of Korea. The distance of otter board, net height, trawl speed and resistance of the fishing gear were respectively measured according to the change of warp length and towing speed. The results obtained are summarized as follows : 1. The spreading distance of the otter board has been increased straightly according to the increment of towing speed and warp length. The rate of increase by the warp length has been greatly higher than the rate of increase by the towing speed. The total variation of the spreading distance was 57.0-82.8m, and it was occupied 43-62% of the hand rope, net pendent and the length of nets. 2. The height of net mouth has been decreased straightly according to the increment of towing speed and warp length. The rate of decrease by the towing speed has been greatly higher than the decrease rate of the warp length. The total variation of the net height was 3.1-4.0m. 3. When the distance of wing tip is increased, the height of net mouth is decreased, but the ratio of the decreasing rate of the height of net mouth for the increasing rate of the distance of wing tip was gradually low according to the increment of warp length. 4. The ratio of the distance of both wing tip for the height of net mouth has been increased gradually according to the increment of towing speed and warp length, and the total variation of the ratio was 4.17-7.81 times.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.38 no.4
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• pp.271-277
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• 2002

This paper was described on the characteristics of bottlenose dolphin (Tursiops truncatus) whistle to develop a warning and attracting acoustic system which can be made friends woith environment and minimized to the fishing pollution from Cetaceans. The experiment for the acoustics of bottlenose dolphin whistle was carried out in dolphin performance hall at Seoul Grand Park during 18th~19th April, 2002. The frequency and the spectrum level of whistle a same pool were revealed 6~10KHz and 85㏈ but those revealed two harmonic waves a 6.7KHz and 21.3KHz for the frequency and 110㏈ and 94㏈ for the spectrum level, respectively, when a dolphin isolated from others. The range of frequency change of whistle was 3.86KHz and continuous time was 0.08 sec. The range of frequency change 10.20 KHz higher as 14.06 KHz and continuous time was 0.11sec longer as 0.19sec when a dolphin isolated from others. By the Mann-Whitney test for the result, there was a significant difference for the range of frequency change and continuous time between normal condition and when a dolphin was isolated from others. The pattern of whistle at the dolphin performance hall was five types and the frequency was getting increased slowly in the range of 5~10KHz at normal condition but there were pattern change of 5~20KHz at the isolated condition. Therefore it is thought that these experiments would be valuable for the development of acoustic system.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.37 no.4
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• pp.267-274
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• 2001

A prototype experiment on the anchovy boat seine was carried out in the southern sea of korea to analyze the vertical opening and the underwater geometry. The vertical opening and the underwater geometry of the prototype net were determined by distance of Minilog position with the combinations of the distance between paired boats and the towing speed. The results osbtained can be summarized as follows; 1. Vertical opening of the protype net was gradually lowered according to the increase of the distance between paired beats and the towing speed. 2. Vertical opening of Wing net, Inside wing net, Square, Fore bag net, Flapper and After bag net of the prototype net according to the distance between paired boats were varied in the range of 8.4~9.0, 15.7~17.4, 12.9~17.9, 13.6~19.0, 8.3~8.4, 11.1~14.7m respectively, varied in the range of 12~16, 22~24, 27~38, 59~83, 92~93, 41~54% of the normal opening respectively. 3. Vertical opening of Wing net, In side wing net, Square, Fore bag net, Flapper and After bag net of the prototype net according to the towing speed were varied in the range of 7.7~10.5, 19.6~21.6, 12.2~16.9, 15.4~17.1, 8.0~8.2, 13.7~14.7m respectively, varied in the range of 14~19, 27~30, 32~36, 67~74, 89~91, 51~54% of the normal opening respectively. 4. Prototype net was appeared apparent the pocket shape, because Wing net and Inside wing net was opened 20% of the normal opening. 5. Working depth of the prototype net was gradually shallow according to the increase of the distance between paired boats and the towing speed.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.39 no.4
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• pp.337-346
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• 2003

This paper describes on the system and method for automatically tracking and real-time monitoring the position of target ships relative to the own ship using a PC based radar system that displays radar images and electronic charts together on a single PC screen. This system includes a simulator for generating the GGA and VTG information of target ships and a simulator for generating the TTM and OSD outputs from a ARPA radar and then host computer accepts NMEA0183 sentences on the maneuvering information of target ships from these simulators. The results obtained are summarized as follows；1. The system developed this study can be used as a range finder for measuring the distance between two ships and as a device for providing the maneuvering information such as distance and bearing to target ships from own ship on ECS screen. 2. From the result of position tracking for a selected target ship tracked with an update rate of 5 seconds using the $\alpha$-$\beta$ tracker, we concluded that the smoothing effect by the $\alpha$-$\beta$tracker was very effective and stable except in the time interval until about one minute after the target is detected. 3. From the fact that the real-time maneuvering information of tracked ship targets via a local area network (LAN) from a host computer installed a radar target extractor was successfully transferred to various monitoring computers of ship, we concluded that this system can be used as a sub-monitoring system of ARPA radar.

• Journal of Fisheries and Marine Sciences Education
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• v.8 no.1
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• pp.41-47
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• 1996

The fishing experiment was carried out in order to analyses the mesh selectivity for trawl cod - end in the Southern Korean Sea and East China Sea from June,1991 through December, 1992. The mesh selectivity was examined for the five kinds with opening mesh size, of which having mesh s izes 51.2mm, 70.2mm, 77.6mm, 88.0mm and 111.2mm. In this report, mesh selectivity were taken analyses trawl cod - end for Priacanthus macracanthus. The main results obtained were as follows : 1. The relation equations between total length(TL) and body height(BH), body girth(BG) and body weight(BW) were BH=0.256 TL+2.963, BG=0.620 TL+8.650 and $BW=7.34{\times}10^{-5}TL^{2.6956}$, respectively. 2. 50% selection length and selection factor of trial cod - end with opening mesh size having 51.2mm, 70.2mm, 77.6mm, 88.0mm were 94.8mm, 1.85 ; 159mm, 2.27 ; 204mm, 2.09 ; 217.3mm, 2.18, respectively. 3. Range of opening mesh size from 51.2mm to 88.0mm, parameters of master curve were slope 2.70, intercept - 5.7 and selection factor 2.11.

• Ocean and Polar Research
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• v.40 no.2
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• pp.69-75
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• 2018

We investigated the effects of environmental variations on the growth and survival rate of Stichopus japonicus to determine the optimum environmental conditions for its growth. Literature studies and a 12 month-long diver survey were carried out to understand the habitat, ecology and size of the surveyed area. Based on the collected data, we suggested optimum habitat conditions for releasing S. japonicus. Experiments on releasing S. japonicus were conducted in the breakwater of the Hwagye fishing cooperative in Hwagey-ri, Namhae-un, Gyeongsangnam-do, Korea. To implement the experiments, we divided the surveyed area into 4 sub-areas with different characteristics: (1) sand and silt zone; (2) artificial sea cucumber bank zone; (3) artificial rock bank zone; and (4) marine algae zone. The experiment lasted for 12 months. We released 32,000 sea cucumbers over $120m^2$ of each of the sand and silt zone, artificial rock bank zone and marine algae zone and released 6,000 sea cucumbers over $120m^2$ of the artificial sea cucumber bank zone. The average density of the released sea cucumbers from day 30 to day 360 after the releasing was conducted was the highest in the artificial sea cucumber bank zone ($23.7animal/m^2$), which was followed by artificial rock bank zone ($2.0animal/m^2$), marine algae zone ($1.9animal/m^2$) and sand and silt zone ($0.8animal/m^2$). The analysis on growth showed that the initial average weight of 2.3 g increased on day 360 after the releasing to 12.5 g in the artificial sea cucumber rank zone, 20.2 g in the sand and silt zone, 23.3 g in the artificial rock bank zone and 22.9 g in the marine algae zone. Results from the experiment along with the literature analysis suggest the following optimum habitat conditions: $10-15^{\circ}C$ water temperature; 28-34 psu salinity; 5-10 m water depth; 0.2-0.5 m/s velocity; rock, stone and muddy sand as substrate; and less than 20% mud in the substrate.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.34 no.1
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• pp.13-20
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• 1998

The moving behaviour of Yellowtail Seriola quinqueradiata schools in the main-net of a large scale set-net was investigated in relation to the catching function of the funnel-net by a scanning sonar. The investigation was took place in the Kishihata set-net fishing ground located in Nanao city Ishigawa prefecture, Japan from Nov. 9 to Nov. 13, 1992. The obtained results are summarized as follows; 1. Fish schools showed the greatest number at the playground in the morning and at the bag-net in the afternoon. The fish schools remained long time in the main-net. 2. The rate of fish school through the funnel-net was smaller than that of fish school which is though the playground and bag-net. Because the Yellowtail school changed the shape of school in passing the funnel-net. 3. The rate of entering the bag-net was 24%, among the fish school heading to the outer funnel-net. But, the rate of escaping to the playground was 27%, among the fish school heading to the inner funnel-net. It seems that the structure of the outer funnel-net was not enough to lead the fish to the bag-net. However, the structure of the inner funnel-net was very effective at preventing escape. 4. It is appropriate to haul the net in the morning in considering the number of accumulated fish in the bag-net during the survey.