Bo-Kyu Hwang

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

Visual census and hydro-acoustic survey of demersal fish aggregations in Ulju small scale marine ranching area (MRA), Korea

Visual census and hydro-acoustic survey was carried out at Ulju small scale marine ranching area (MRA) to estimate demersal fish aggregations on September and November 2013. In this hydro-acoustic survey, the authors combined an image sonar with a scientific echo sounder to monitor an underwater situation and compare two acoustic data. Consequently, visual census survey was useful to estimate fish species composition for hydro-acoustic survey, because it is easy to identify aggregated fish species and overcome limits on a fishing depth and ability of an conventional fishing gear like a bottom gill-net or a fish trap at marine ranching area. Mean fish density was estimated as on September and on November and Fish abundance was finally calculated as 1.51ton (coefficient of variation, CV

Spatial characteristics of fish distribution lured by artificial reefs in Jeju marine ranching area

서 론 근래 우리나라 수산업은 UN해양법 협약의 발효에 따 른 해외어장 축소로 인하여, 연근해 어업자원의 중요성 은 날이 갈수록 높아지고 있으나, 연안환경의 오염은 날 이 갈수록 심해짐에 따라 어업자원량의 감소가 두드러 지게 나타나고 있으며 매년 적조생물의 대량 발생으로 피해가 속출하고 있는 실정이다. 또한, 수산물 수입 자 유화로 중국산 저가 수산물이 대량으로 보급되고 있고, 어업인구의 지속적인 감소와 노령화 등으로 연근해 어 업의 경쟁력은 더더욱 악화되고 있다. 이에 우리나라에 서는 지난 1970년대를 시작으로 인공어초 시설사업 등 을 통해 인위적으로 수산 동식물의 서식공간을 조성하 여 연근해 어업의 어업 생산성을 향상시키기 위해 노력 하여 왔다. 또한, 1990년대 후반에는 바다목장 사업을 통하여 본격적으로 인공어초 부설사업이 진행되었으 며, 현재 동해, 서해, 남해 및 제주에 이르기까지 방대한 양의 인공어초가 부설되어 이를 통한 연근해 어업자원 의 효율적인 관리와 잠재적 생산력 증대를 도모하고 어 민소득의 증대와 수산물 공급의 안정화를 꾀하고 있다. 막대한 자본을 투자해야 하는 인공어초 사업은 그 효 과를 평가하기 위한 적절한 방법을 강구할 필요가 있다 (Lee, 2013). 현재 인공 어초 조사는 소나 나 다이버를 이 제주 바다목장 해역의 인공어초에 유집된 어군 분포의 공간적 특성

Acoustic characteristics of Anchovy schools, and visualization of their connection with water temperature and salinity in the Southwestern Sea and the Westsouthern Sea of South Korea.

Morphological and positional characteristics of anchovy aggregations, confirmed by trawling, were examined in two locations of the southern part of theWest Sea (T1) and the western side of South Sea (T11) of South Korea. Morphological characteristics (mean length, height and area) of the anchovy aggregations at T1 were smaller than those at T11, however the positional characteristics (distributional depth and bottom depth) of the aggregations at T1 were larger than those at T11. Diverse dataset such as the ship`s cruise track, the cruse map, and interpolated three-dimensional-like water temperature were visualized in multiple dimensions. For a comprehensive understanding of the anchovy aggregations within their surrounding circumstances, the interpolated water temperature transferred to the location of anchovy aggregations at both stations were visualized based on geospatial information. Using quantitative investigation, the overall range of change in water temperature and salinity of anchovy aggregations at stations was considerably small. However, the water temperature and salinity of anchovy aggregations at T11 were somewhat higher than those at T1.

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.

A quantitative analysis of greenhouse gases emissions from bottom pair trawl using a LCA method

The negative factors of fishery in environmental aspect of view are Greenhouse gas emission problems by high usage of fossil fuel, destruction of underwater ecosystem by bottom trawls, reduction of resources by fishing and damage of ecosystem diversity. Especially, the Greenhouse gas emission from fisheries is an important issue due to Cancn meeting, Mexico in 1992 and Kyoto protocol in 2005. However, the investigation on the GHG emissions from Korean fisheries did not much carry out. Therefore, the quantitative analysis of GHG emissions from Korean fishery industry is needed as a first step to find a relevant way to reduce GHG emissions from fisheries. The purpose of this research is to investigate which degree of GHG emitted from fishery. Here, we calculated the GHG emission from Korean bottom pair trawl fishery using the LCA (Life Cycle Assessment) method. The system boundary and input parameters for each process level are defined for LCA analysis. The fuel use coefficient of the fishery is also calculated. The GHG emissions from the representative fishes caught by bottom pair trawl will be dealt with. Furthermore, the GHG emissions for the edible weight of fishes are calculated with consideration to the different consuming areas and slaughtering process also. The results will be helpful to understand the circumstances of GHG emissions from Korean fisheries.

Morphological Properties and Target Strength Characteristics for dark banded rockfish (Sebastes inermis)

Morphological properties of dark banded rockfish (Sebastes inermis) were analysed to investigate its acoustic scattering characteristics. Total of 18 live samples was prepared for X-ray photos and collected morphological coordinates of their body and swim bladder shapes. Kirchhoff-ray mode model was used to calculate acoustic scattering pattern for broad-band frequency range. Inclination of swim bladder ranged from 17 to 30 and the averaged value was about (S.D.(standard deviation)

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.

Verification and application of Target Strength for Japanese anchovy (Engraulis japonicas) by theoretical acoustic scattering model

Acoustical backscattering characteristics of Japanese anchovy can be estimated by Kirchhoffray mode model (KRM model) due to estimate exact body and swim-bladder shape of the fish, the samples were rapidly frozen by dry-ice and alcohol. X-ray photos for ventral and lateral direction for 6 samples were taken and the 3D coordinates of the body swim-bladder were estimated by digitizing from the photos. The angles between the axis of body and swim-bladder were about at 38kHz and at 120kHz, 200kHz. General formula of TS and BL estimated were >

Energy Consumption and Greenhouse Gas Emission of Korean Offshore Fisheries

This paper presents the energy and greenhouse gas (GHG) emission assessments of Korean offshore fisheries. The consumption of energy by fisheries is a significant concern because of its attendant environmental effect, as well as the cost of the fuel consumed in fishing industry. With the global attention of reducing GHG emission and increasing energy efficiency of fuel, the seafood industry needs to further understand its energy use and reduce its GHG emission. In the present study, the amount of energy consumed and the GHG emission of Korean offshore fisheries in a period from 2009 to 2013 were examined. Offshore fisheries accounted for 24% of Korean production in 2013 and 60% of fuel consumption related GHG emission. Whereas the total GHG emission intensity of this sector improved slightly between 2009 and 2012; as such emission decreased by approximately 1.9%, which increased again in 2013. The average amount of total GHG emission in this five years period was 1.78 × 106 tons of carbon dioxide equivalent/year (t CO2 eq. y−1). Active fishing gear was found to consume 20% more fuel than passive gear. However, the production from passive gear was 28%, lower than 72% from active gear. The reason for this is that less abundant stationary resources are harvested using passive gear. Furthermore, the consumption of fuel was significantly influenced by the fishing method. Implementation and development of new fishing technologies and methods are important for improving energy efficiency and reducing the climate impact on fisheries. To realize these purposes, the fishery management system needs to be established by centralizing on energy efficiency and climate effect.