Recently, domestic fishing production of Japanese horse mackerel has been continuously decreasing. To achieve sustainable fishing of this species, it is essential to acquire its target strength (TS) for accurate biomass estimation and to study its ecological characteristics. To date, there has been no TS research using a broadband echosounder targeting Japanese horse mackerel. In this study, for the first time, we synchronized an underwater camera with a broadband frequency (nominal center frequency of 200 kHz, range: 160-260 kHz) to measure the TS according to the body size (16.8-35.5 cm) and swimming angle of the species. The relationship between Japanese horse mackerel length and body weight showed a general tendency for body weight to increase as length increased. The pattern of the frequency spectra (average values) by body length exhibited a similar trend regardless of body length, with no significant fluctuations in frequency observed. The lowest TS value was observed at 243 kHz while the highest TS values were recorded at 180 and 257.5 kHz. The frequency spectra for the swimming angles appeared to be flat at angles of –5, 0, 30, 60, 75, and 80° while detecting more general trends of frequency spectra for swimming angle proved challenging. The results of this study can serve as fundamental data for Japanese horse mackerel biomass estimation and ecological research.

To understand differences of environmental factors and planktonic communities in closed (CS) versus open (OS) enclosed experimental systems, we performed a study on a 100-L indoor- type artificial marine microcosm. For environmental factors, including water temperature, dissolved inorganic phosphorus, and dissolved silica, there were no significant differences between CS and OS; however, salinity was higher in CS than that of OS due to the evaporation effect. The concentration of dissolved oxygen and dissolved inorganic nitrogen was lower in CS than in OS. The abundance of phytoplankton was lower in CS than in OS. However, abundance of autotrophic nanoflagellates and heterotrophic bacteria varied inversely with that of phytoplankton abundances. In particular, the abundance of heterotrophic nanoflagellates and ciliates increased with bacterial growth after a time lag. Therefore, environmental factors and planktonic communities in CS gradually changed over time and characterized a different artificial ecosystem than in OS.

Acoustic side-aspect target strength (TS) of living Japanese anchovy (Engraulis japonicus) was measured at 120kHz during in situ experiments. The data were collected by lowering and horizontally projecting the splitbeam transducer into the anchovy school. For analysis and interpretation of the side-aspect TS data, acoustic theoretical model, based on the fish morphology, and dorsal-aspect TS data were used. Total length of the anchovy ranged from 6.6 to 12.8cm (mean length 9.3cm). The side-aspect TS distributed between -40 and -55dB, has an obvious length dependency. The mean side-aspect TS of the anchovy was -47.8dB, and the TS was about 2dB higher than mean TS generated from dorsal-aspect measurements. With reference to maximum TS, the results of the side-aspect TS were distributed within the range of the theoretical and dorsal-aspect TS. Apparently these tendency indicates that side-aspect TS measured from the study is useful data. These in situ measurements of side-aspect TS can be applied to improve acoustic detection and estimates of the anchovy, and is necessary to measure with a various frequency and length for making enhance data.

Acoustic telemetry technique is one of useful tools to get behavioral information of the free-swimming fish. In this study, we conducted acoustic telemetry using coded acoustic transmitters to compare behavior characteristics between wild and cultured black seabream Acanthopagrus schlegeli, one of target species to promote resource in the marine ranching area. Two wild fish and five cultured fish were released in the marine ranching area after tagging surgically. Three of cultured fish were domesticated using the remote acoustic conditioning system for 3 weeks before being released. Two wild fish stayed at the released point for 2 hours and 9 days, respectively. One of wild fish was found about 10.8km away from the released point after 5 months. Two cultured fish stayed at the released point for 6 days and 75 days, respectively. One of acoustic conditioned fish stayed at the released point for 131 days and then was found about 10.1km away from the released point after 25 days. Others stayed at the released point during this study period(159 days).

Assessment and management of fisheries abundance in fresh water like a river or a lake is very important to maintain fisheries itself as well as tourist industry even if their scale is not much large. The species for catch in fresh water are mainly a mandarin fish, a carp, an eel, and others. Because oriental river prawn is a main prey of these species and the change in its abundance is directly related to their abundance change in fresh water, information on the abundance and distribution of the species are necessary. Hydroacoustic survey is known to one of the efficient method among several methodology. Information on acoustic target strength is key parameter to estimate abundance for acoustic survey. In this study, measurements on oriental river prawn, Macrobrachium koreana, were conducted for two high frequencies(200kHz and 420kHz) with tilt angle using automatic rotating system. The results of acoustic target strength obtained from the experiment were compared with those of acoustic scattering model, Distorted Wave Born Approximation(DWBA) model. For 200kHz, the result of acoustic target strength experiments was expressed in terms of the averaged target strength dependence on the body langth(BL, cm) as a following relationship; 〈 TS200kHz 〉 = 45.9log(BL) - 107.4. These results provide basic information for studying acoustic target strength and conducting acoustic survey of oriental river prawn.

황해 주요어족생물의 분포 특성을 파악하기 위한 연구의 일환으로 황해의 위도 33˚00'N~37˚00'N, 경도 24˚00'E~126˚00'E를 대상 해역으로 설정하여, 1999년 5월, 1999년 8월, 2000년 4월의 3회에 걸쳐 여수대학교 실습선 청경호와 동백호를 사용하여 실시한 해양학적 및 음향학적조사에 대한 결과를 요약하면 다음과 같다. 1. 조사당시 황해 저층수온의 지리적인 분포는 제주도 서부해역, 목포 서부해역, 군산 서부해역의 3권역으로 크게 구분되었고, 수온차는 제주도 서부해역이 군산 서부해역보다 2~5℃ 정도 높았다. 또한 어족생물자원의 분포와 관련이 깊은 수온 약층(thermocline)은 5월보다는 8월에 뚜렷하게 형성되었다. 2. 황해의 조사대상해역에 대한 면적산란계수는 값은 38kHz의 경우, 제주도 서부해역에서 가장 높게 나타났고, 위도가 높을수록 낮은 경향을 나타내었다. 그러나 120kHz의 경우에 있어서는 38kHz와 다른 양상을 보여 제주도 서부해역에서 보다는 목포 및 군산 서부해역에서 상대적으로 높은 값을 나타내었다. 3. 면적산란계수의 연직분포는 수온약층(thermocline)을 경계로 그 값이 뚜렷하게 구분되었는데, 수온약층이 발달된 해역일수록 표출부 저층부에서의 면적 산란계수가 높았고, 동서방향에 대해서는 연안이나 근해쪽보다는 그 중심부근에서 면적산란계수가 높은 경향을 나타내었다. 4. 트롤망고에 해당되는 저층 5m에 대한 면적 산란계수의 값은 대체적으로 어획량에 비례하는 경향을 나타내었고, 서식 어종의 차이에 따라 저층성 어종은 38kHz에서, 중층성 어종은 120kHz에서 면적산란계수가 높게 나타나는 경향을 보였다.분형 최적제어계의 실험결과를 통한 엄밀한 제어성능검증과 스텝외란 외의 주기성 외란 인가시 2자유도 적분형 최적제어계의 외란제거 방안 등이 검토되어야 할 것으로 사료된다.중방사음역에 있어서의 시간응답특성을 조사한 결과, 그 응답특성은 송신전압감도의 주파수특성과 매우 잘 일치하는 경향을 나타내었다. 이상의 결과로부터 본 연구에서 설계, 제작한 이중정합층을 갖는 복합구조 초음파 변환기는 단순구조의 Tonpilz형 초음파 변환기와 비교하여 비록 송파전압감도에 있어서는 약 5 dB 정도의 음향출력의 손실이 불가피하지만, 그 대신 주파수 대역폭을 약 5 재 정도 확대시킬 수 있는 장점이 있기 때문에 이 넓은 주파수 대역을 효과적으로 활용하면 어종식별을 위한 음향산란신호를 정량적으로 수집 및 평가하는 것이 가능하다고 판단된다.n A was 11 ug.이, 0.9 ug/g and 3.7 ug/g in the blood, liver and kidney, respectively.sional-managerial who secure the higher autonomy and stability in their work have the highest life chance in the labor and health, and leisure life. Next, professional-technical, white-collar, sales-service occupants have the higher life chance after the professional-managerial. However, these 3 occupation groups are partially inconsistent in the two sectors of the life chance. Specifically, the professional-technical, despite their autonomy a