Distribution and composition of the seabed litters in the exclusive economic zone of the West Sea of South Korea including 18 sea-blocks were investigated using a bottom trawl gear of the R/V Tamgtu 20 (National Institute of Fisheries Science) from 24th April 2011 to 4th May 2012. Each trawl shot was conducted for an hour in each sea-block and the total trawl shots was 18. As a result, 325.6 kg of seabed litter in total has been collected.　The quantity of the seabed litter was highest at No. 202 of the sea-block, close to the Heuksan-Do. The highest occupied sea material was plastic (83.1% of entire seabed litters), the second highest material was metal combined with plastic (10.6%), and glass (2.9%), metals (2.3%), vinyl (0.6%), cloth (0.4%) and wood (0.2%) in order. The origin of seabed litters was from fishing gear (89.0% of all seabed litters). Therefore, it could be assumed that most seabed litters were derived from the fishing activity for example fishing nets and ropes.

For scientific research, a number of acoustic surveys using commercial echosounders equipped in fishing vessels were conducted throughout the world; however, few studies were performed in South Korea. Hence, this research is an preliminary study for presenting the application of a sounder from a fishing vessel. The fishing operations using a pair trawler (7 Cheonghae) was conducted in the Northwest-Western sea of Jeju Island from 20 to 23 April, 2016. Substantial impulse noises and attenuated signals were eliminated by the latest algorithms. Acoustic signals were grouped into the fish aggregations and long layer-like signals. The fish aggregations appeared between 30 and 60 m, and long layer-like signals showed the diurnal vertical migration. Energetic, morphological and positional properties of the fish aggregations and layer-like signals were described. The fish aggregations appeared mainly between sunrise and sunset; however layer-like signals tended to be presented regardless of time in consideration of the time series analysis. On the basis of the consignment sales, Scomberomorus niphonius, the target species of F/V 7 Cheonghae, was the highest catch with 4,280 kg (74.6%) and might have appeared in fish aggregations and layer forms.

The objective of this study was to provide fundamental information on fish swimming behavioral properties. Acoustic data was collected at nighttime from the 10th to 12th March, 2016 near Yokji Island in the South Sea of South Korea, and was analyzed using the fish track technique. This technique is to identify groups of single targets, which shows a pattern of systematic movement. As a result, the differences of the behavioral properties such as depth, swimming speed, vertical direction, horizontal direction, tortuosity, and depth change among days were minor; however, statistical results (Welch analysis of variance) showed significant difference between days. Especially, the target strength (TS) of the 11th were significantly different from the 10th and 12th. It could be assumed that gizzard shad, which was the dominant species from the catch on the 11th March, might have affected this difference. The correlation between TS and other properties was very week. The significant difference seemed even small differences of average values because of the large data volume.

Properties of aggregation and spatial distribution of fish were examined based on three lines in the South Sea of Korea using three frequencies (18, 38, and 120 kHz) of a scientific echosounder. The vertical distribution of fish was displayed using acoustic biomass namely nautical area scattering coefficient (NASC). As a result, at 120 kHz high NASC showed from water surface to 20 meters in deep while at 18 and 38 kHz very high NASC presented in 70 ~ 90 meters in depth, especially at line 3. Among three lines, the line 2 had lowest NASC. The horizontal distribution of fish using three frequencies together exhibited high NASC between the eastern South Sea and center of South Sea. In especial, NASC (801 ~ 1,920 m2/n·mile2) was observed along coastal waters from Busan to Tongyeong, Geoje, and Namhae. In regard with the property of aggregation of fish schools, the volume back-scattering strength (SV) of three lines presented close each other, however, the range of SV in the line 2 was shortest (-53.5 ~ -43.4 dB). The average distributional depth was deep in the order of L3 (32.8 ± 9.0 m), L1 (45.2 ± 9.5m), L2 (49.7 ± 5.6 m). The average altitude was high in the order of L3 (13.4 ± 10.3 m), L1 (17.0 ± 12.6 m), L2 (56.7 ± 5.6 m). The average length, thickness, and area were large in the order of L1, L3, and L2. This means that small sized fish schools were distributed near water surface in the line 2 while relatively large and similar sized fish aggregations between line 1 and line 3 appeared however, fish schools at line 3 had lower distributional depth and smaller compared to those at line 1. Acoustic data were visualized for demonstrating the entire circumstances of survey area. Additionally, there was no correlation between acoustic and trawl results.

This study attempted to help determine Korean fishery policies by proposing improvement plans after examining the current regulations, fishing vessels, fishing gear and fishing methods of the middle sized trawl fishery in the East Sea for targeting only squid. In general, the size, engine horse power, and net length of the middle sized trawlers are between 50 and 60 GT, 1,200 and 1,600 PS, and approximately 165 m with four seamed trawl nets, respectively. While a jigging vessel attracted squids using lights, the trawler approached a jigging vessel. The trawler let the jigging vessel know its decision for fishing, and then jigging vessel rolled up jigs. The net of the trawler was casted at 45 degrees between the bow and the stern of the jigging vessel. Once the trawler towed close to the stern of the jigging vessel upon its passing of the jigging vessel, the bow of the trawler turned 45 degrees left again. Then, squid aggregations were entered into the net. When the cod end was passed a light vessel, the trawler hoisted the net up to the otter board. Then the trawler turned 180 degrees. It repeated three to five times of fishing operations as the previous method. We recommend that the regulations allow nineteen side trawlers to catch like stern trawler, as well as the cooperative trawler and jigging vessel operations.

Acoustic surveys using a scientific echosounder and trawl surveys were concurrently carried out in between Geoje and Tongyeong of the South Sea by season. The anchovy schools were identified by trawling in each station and used for frequency response analysis. Frequency responses of anchovy schools by season and species composition ratio were examined using multi-frequencies (18, 38, 70, 120 and 200 kHz). The frequency response r(f), is one of the acoustic characteristics which means the volume back-scattering strength ratio between a reference frequency and other frequencies. In spring, the r(f) of anchovy schools decreased with increased frequency, with the exception of 120kHz. While, in winter, the r(f) continuously decreased inversely proportional to the increase in frequency. Frequency response of anchovy schools presented a distinctive difference between spring and winter, however it did not different in spife of different species composition ratios in schools.

An acoustic and trawl pilot survey using a small vessel was conducted in Jinhae bay of the South Sea of South Korea on April 13~14, May 11~13 and June 8~10, 2015. During the survey, acoustic data was collected and bottom trawls were conducted at the same time. First, various noises were eliminated by using the Park method based on the Wang method(Wang et al., 2015; Park et al., 2015), the species compositions and catch rate from each bottom trawl were observed, and spatial distribution of fishery resources in the water column and their nautical area scattering coefficient (NASC) were investigated through acoustic data. During the entire survey period, 12 orders, 33 families and 41 species were caught. The most caught species in April, May and June were Okamejei kenojei, Zoarces gilli and Pholis nebulosa, respectively. Fish schools were observed near the line of net mouth height in April. Numerous weak scatters were presented on the echograms in May and June. Many fish schools appeared in between the water surface and 20 m deep in May. The NASC value from entire water columns was the lowest in April (35.9 m2/n･mile2) and highest in June (1541.3 m2/n･mile2).

The hydro–acoustic technology has been widely used in not only South Korea but also many foreign countries for various scientific purposes. Unfortunately acoustic data especially collected from field surveys may contain noises caused by a variety of sources. Therefore, it is exceedingly important to eliminate noises when acoustic data are analyzed to derive quantitative results. This study introduced two methods for eliminating noises easily and effectively using post–processing software. Used acoustic data were collected on the Jinhae bay and Tongyeong coast of the South Sea in April 2015. The first method, that is the Wang’s method, placed emphasis on ‘erosion filter’ to eliminate only data samples contaminated by noises. The second method (Yamandu’s method) focused on the ‘resample by number of pings’ to remove pings contained noises. To substantiate the effectiveness of two methods, the mean Sv (Volume backscattering strength), mean height and depth of the fish schools detected were compared between before and after using the noise elimination methods. In the Wang’s method the mean Sv was decreased from –52.4 dB to –52.9 dB, and in the Yamandu’s method from –52.6 dB to –53.3 dB, indicating that noises were successfully eliminated. The mean height (1.5 m) and depth (19.0 m) were same between before and after using two methods showing that the shapes of fish schools were not changed.

The multi-frequency characteristics of anchovy schools were investigated using six acoustic lines collected at 38 and 120 kHz while a primary trawl survey was conducted from 14 April and 18 April of 2014 in off the coast of Tongyeong and Geo–je. Here, the frequency characteristics mean ΔMVBS that is the difference of Mean Volume Backscattering Strength at two frequencies. To use the characteristics effectively, the optimal cell size (10×2 m) was determined by examining several different cell sizes in consideration with the shapes of fish schools and the ΔMVBS pattern. By examining 6 histograms of ΔMVBS, afternoon groups were occupied more in the ΔMVBS range of –6~–4 dB than that of –4~–2 dB, comparing to morning groups. The ΔMVBS range of the morning groups was between –16.9 dB and 11.6 dB, and that of the afternoon groups –16.7 dB and 13.0 dB. The average and standard deviation were –3.9±3.6 dB in the morning and –4.1±3.4 dB in the afternoon, suggesting that morning groups were 2 dB higher than afternoon groups. The ΔMVBS range of all anchovy schools regardless of morning and afternoon was between –16.9 dB and 13.0 dB, their average ΔMVBS was –4.1±3.5 dB. The characteristics can support to identify anchovy species in the waters where multiple fish species are distributed. It is hoped that this study presents the availability and benefit of acoustic data from a primary trawl survey.

부정관(不淨觀)은 수식관(數息觀)과 더불어 초기불교의 핵심적인 붓다의 수행법 중 하나이다. 비구들의 욕심, 특히 성적 욕심의 제도 를 목적으로 했던 부정관은 몸의 36가지의 부정물을 관찰하고, 무덤 가에서 여러 시신부패의 모습과 변화의 모습을 보고 이를 통하여 자 신을 안으로 관찰하는 것이었다. 그래서 초기불교의『염처경』등 여 러 경전에서는 몸의 부정을 관찰하는 부정관 관법을 내신(內身)을 중 심으로 하여 시설한 것이다. 그러나 이러한 부정관이 폐기되고 안나반나염(安那般那念)이라는 새로운 수행법이 시설되는 계기가 있었는데, 여기에는 교단 내 큰 사 건이 일어났기 때문이다. 즉 부정관을 닦는 비구들이 부정관을 열심 히 수행한 결과, 피와 고름이 흐르는 등의 몸의 현상을 경험하고 몸을 극도로 싫어하게 되어서 자살에까지 이른 사건이 일어났기 때문이다. 사건의 시발은 부정관을 열심히 닦던 한 비구가 옷과 발우를 주겠다 는 조건으로 다른 사람을 시켜 자신을 죽여 달라고 부탁한 것에서 비 롯된다. 살해자는 자신의 행위를 처음에는 후회하나 천마(天魔)의 권 청으로 살해가 오히려 비구를 열반시킨 것으로 착각하여 수행처 곳곳 을 다니며 몸의 현상에 괴로워하던 비구 60명을 죽이게 된다. 그러나이사건의일화를기록한『잡아함경』제29권,『 마하승기율』 제4권,『 사분율』제2권,『 오분율』제2권,『 십송률』제2권,『 근본설일 체유부비나야』제7권은 그 전모에 대해서는 동일하게 기록하고 있으 나 결정적 내용에서 다르게 기술하고 있다. 사건의 전개과정과 시설처, 붓다의 부정관 찬탄, 비구들의 자살의 형태, 천마의 권유, 60명의 비구의 살해에 대해서 약간의 차이를 보 이며, 60명의 비구를 살해한 살해자의 신분은 다르게 기록하고 있다. 특히 이 참혹상에 대한 재가자들의 비난내용은『사분율』을 제외한 다 른 경전과 율전에는 기록되어 있지 않다. 사건의 전개과정을 밝힌 부정관의 일화 속에서 본 논문은 당시의 수행상과 더불어 사건의 시설처, 주체, 부정관의 폐해상을 상세하게 밝혔다. 특히『사분율』제2권은 다른 경율과 다르게 60명 비구의 살 해자가 바라문과 외도, 전다라가 아닌 물력가난제(勿力伽難提) 비구 라고 밝히고 있으며, 참혹상을 본 재가자들의 비난의 소리도 생생하 게 밝히고 있다. 여기에서 상좌부를 제외한 각 부파 교단은 교단내의 엄청난 살해사건을 숨기고 싶었던 의도가 있었음을 알 수 있었다.

Anchovy (Engraulis japonicus) is one of the most important species in the South Sea of South Korea. In order to estimate the biomass of anchovy, acoustic surveys, concurrently with trawling, were conducted in April, July, and September of 2013 and February of 2014 off the coast of Tongyeong and Yeosu. However, anchovies were found only during spring (April) and winter (February) surveys. To display only anchovy species confirmed by trawls on empty spaced echograms, virtual echograms were created. Three target strength (TS) values of anchovy were used: TS_z = 20 log L – (20/3) log (1+z/10) – 67.6 (Zhao et al.), TS_y =20 log L – 72.9 (Yoon et al.), TS_f = 20 log L – 71.9 (Foote). For anchovy schools combined with other species e.g., hairtail, squid, and Korean pomfret, their TS values were used to calculate an average TS. As a result, the anchovy biomass in the winter survey was approximately 75,000 tons (TS_z), 90,000 tons (TS_f), 114,000 tons (TS_y), respectively. The biomass in spring was 9,000 tons (TS_z), 9,200 tons (TS_f), 10,000 tons (TS_y). The sampling variance of spring was 70% and of winter was 30%. In order to manage anchovy resource sustainably, larvae and adult anchovy should be separately surveyed, the optimal area, date, and time for acoustic survey should be investigated, and the biomass survey should be done for relatively long and regular base.

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 0.757 g/m2 on September and 0.219 g/m2 on November and Fish abundance was finally calculated as 1.51ton (coefficient of variation, CV=13.1%) on September and 0.44ton (CV=47.7%) on November, respectively. Hydro-acoustic survey combined with the image sonar was useful to monitor fish aggregations and estimate fish stocks around artificial reefs at shallow coastal MRA. We were able to easily identify the underwater structures like an artificial reef and a fishing rope as well as fish aggregations from image sonar data. Therefore, the method was effective to separate unwanted echo signals in acoustic data of scientific echo sounder.

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.

An acoustic method for discriminating plankton from fish, in Lake Dom Helvecio of Brazil, is developed. The flow of data from this method is comprised of time varied threshold (TVT), dilation filter, bitmap and mask functions. The TVT can, of itself, precisely explain how to select an appropriate value. The final results of the echogram, which only shows plankton by masking fish signals, is used to examine the acoustic density of plankton by depth and time. The results indicate that the acoustic density of the plankton is at a depth of between 5m to 15m, its density is especially high at 10m to 15m. The results of the acoustic density of plankton by time indicate that May 7 is higher in density than May 8. Future study plans include the use of net samples, environmental datasets to identify the abundance and ecology described by the Chaoborus spp. from other species.