Dae-Jae Lee

Verification of mean volume backscattering strength obtained from acoustic Doppler current profiler by using sound scattering layer

Acoustic Doppler current profilers (ADCPs) have recently been used to estimate the dynamic characteristics and biomass of sound scattering layers (SSLs) or swimming speed of fish schools and to analyze SSL spatial distribution or various behavior patterns. This paper shows that it is necessary to verify mean volume backscattering strength (MVBS, dB) values acquired from each beam for quantitative analysis of the spatial distribution or the biomass estimates of such specific targets as SSL or a fish school when using an ADCP. In this study, the SSL was selected to be a homogeneous density layer over a large area and two methods were used to verify the MVBS values from each beam of the ADCP. First, a mutual comparison among four beams was conducted after calculating MVBS from the measured echo intensity. Second, the MVBS values were verified using comparison between the calculated MVBS from the 153.6 kHz ADCP and MVBS from three frequencies of a well-calibrated scientific echosounder. Moreover, the dominant scatterers (euphausiids) were collected by a framed midwater trawl. From these samples, biological data were used to identify the different frequency characteristics between two systems, using a distorted-wave Born approximation (DWBA) theoretical backscattering model in order to assess the averaged target strength and target strength TS differences for the three frequencies.

Fish length dependence of target strength for black rockfish, goldeye rockfish at 70kHz and 120kHz

Black rockfish and goldeye rockfish are commercially important fish species due to the increasing demand in Korea. When estimating the abundance of stocks for these species acoustically, it is of crucial importance to know the target strength(TS) to length dependence. In relation to these needs, TS measurement was conducted on black rockfish and goldeye rockfish in an acrylic salt water tank using 70kHz and 120kHz split beam echo sounders. The TS for these two species under the controlled condition was simultaneously measured with the swimming movement by DVR system and analyzed as a function of fish length(L). The results obtained are summarized as follows: The best fit regression of TS on fish length of black rockfish was TS

Management of coastal and offshore fishing ground using wide-area network of AIS

In order to efficiently manage the coastal and offshore fishing ground, the applicability of real-time monitering was also investigated through a wide-area network of automatic identification system(AIS). The experiment of efficiently managing coastal and offshore fishing ground with a wide-area network of AIS required, on the headquarter`s screen, a synthetic display of vessel information transmitted from three different distant stations. This experiment tested the applicability of real-time monitoring with the shown display. The maximum range of detection of the first station in Busan was 24 nautical miles while those of the second and third stations in Yeosu and Jeju were 26 and 52 nautical miles, respectively.

Swimming speed measurement of Pacific saury (Cololabis saira) using Acoustic Doppler Current Profiler

) migratedoffshore Funka Bay of Hokkaido using an acoustic Doppler current profiler (OceanSurveyor, RDI,153.6kHz) established in T/S Ushio-maru of Hokkaido University, in September 27, 2003. The ADCPsdoppler shift revealed as the raw data that the maximum swimming velocity was measured 163.0cm/s, andits horizontal swimming speed and direction were 72.424.1 cm/s, 160.122.3 while the surroundingcurrent speed and direction were 19.68.4cm/s, 328.1 45.3 . To calculate the actual swimming speed ofPacific saury in each bins, comparisons for each stratified bins must be made between the mean surroundingcurrent velocity vectors, measured for each stratified bin, and its mean swimming velocity vectors, assumedby reference (threshold70dB) and 5dB margin among four beams of ADCP. As a result, the actualaveraged swimming velocity was 88.6cm/s and the averaged 3-D swimming velocity was 91.3cm/s using the3-D velocity vector, respectively. Keywords: Acoustic Doppler Current Profiler, Pacific saury, swimming speed, 3-D velocity vector

Three dimensional visualization of seafloor topography for the application of integrated navigation system

The 3D visualization of seafloor topography(ST) was realized to discuss the effective use by the 3D visualization of ST on the integrated navigation system(INS) for fishing boat. The software was to actually display the 3D visualization of ST using triangular irregular network, helical hyperspatial codes and stereo projection. The INS for fishing boat which applied the 3D visualization of ST will be utilized for safety voyage and the effective fishing work on the fishing ground.

Trial manufacture of dual frequency acoustic pinger to minimize cetacean bycatch

Dual frequency acoustic pinger(AP) was manufactured to reduce study effect by long-term use of developed single frequency AP to prevent cetacean bycatch. Directivity characteristic of transducer was the omnidirectional pattern which showed less than the change range of sensitivity on the beam pattern of right and left. Source power level(SPL) was 1384311pa with epoxy window before casing however after casing 1170B11Pa at sea. Dual frequency Af was tested to identify the avoidance behavior of bottlenose dolphin by its working. However the efficiency of dual frequency AP about the study effect was verified experiment repeatedly using single and dual frequency AP.

Underwater Sound Characteristics of Gray Whale(Eschrichtius robustus)

The underwater sound of California gary whale was analyzed to discuss obtained results from the previous data to compare the underwater sound between Korean gray whale and California gray whale. The frequency of low frequency rumble which occupy about 50% of the underwater sound changed to max. 654Hz and the average of its lasted time was 570msec. The range of frequency variation was coincided as compared with the previous data. The range of frequency variation for the bubble type sounds and knocks was 241029Hz, respectively. The average of lasted time was 1100msec and 1364msec, respectively. The range of frequency variation and lasted time of bubble type sounds was higher than the previous result while the sound of knocks was coincided. The range of frequency variation for the sound of bong, pluses and chirps was 34213Hz, 75360Hz and 120200Hz, respectively and the average of lasted time was 84msec, 873msec and 80msec, respectively.

Verification of mean volume backscattering strength from acoustic doppler current profiler by using calibrated sphere method

ADCPs have been widely used to estimate the dynamic characteristics and biomass of sound scattering layers (SSLs), and swimming speed of fish schools for analyzing SSLs spatial distribution and/or various behavior patterns. This result showed that the verification of the mean volume backscattering strength (MVBS or averaged SV, dB) acquired by the ADCP would be necessary for a quantitative analysis on the spatial distribution and the biomass estimation of the SSLs or fish school when ADCP is used for estimating their biomass. In addition, the calibrated sphere method was used to verify values of each MVBS obtained from 4 beams of ADCP (153.6 kHz) on the base of 3 frequencies (38, 120, 200 kHz) of Scientific echo sounders split beam system. Then, the measured SV values were compared and analyzed in its Target Strength (TS, dB) values estimated by a theoretical acoustic scattering model.Keywords: ADCP, MVBS, Calibrated sphere method, SSLs, Acoustic scattering model

Stabilization of ship s heading in AIS of fishing vessel by a hybrid GPS/EM compass

The ships heading information of hybrid GPS/EM compass were applied to the AIS of fishing vessel andexamined the possibility of accuracy improvement. It is observed 453 each in AIS receiver of land among3,982 each in AIS Rx/Tx transponder of the test ship at sea, and transmission interval according to the speed ofship is determined the 11.4% good transmitting data of the all information. In results, maximum compass errorfor the ship s heading of an EM compass was 19.1 . The variance of ship s heading owing to the speed of shipis surveyed. The COG (Course Over Ground) was changed extremely in 180W-179 E range under 4.9knots,and in 24W-23 E range over 4.9knots. Finally, using the ships heading of EM compass and the COG fromGPS for the autopilot system of a small fishing boat and the ships heading information of AIS results indanger on the own ships navigation safety and leads to make confusion both the others and VTS (VesselTraffic Service) center. Therefore, the hybrid GPS/EM compass is identified as the best system for a smallfishing boat and is allowed to offer continuously a ship s heading information with high accuracy and stability.Key words: Stabilization, Ship s heading, AIS, Hybrid GPS/EM compass, Fishing vessel

Acoustic target strength measurements on immobile riverine shrimp, oriental river prawn(Macrobrachium koreana), in freshwater

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; >