scholarly journals Comparison of Distribution and Density of Nemopilema nomurai by Water Columns Using Echo Counting and Echo Integration Methods

2020 ◽  
Vol 12 (14) ◽  
pp. 5823
Author(s):  
Kyoung Yeon Kim ◽  
Weol Ae Lim ◽  
Jinho Chae ◽  
Gunhee Sung ◽  
Wooseok Oh ◽  
...  
Keyword(s):  
Distribution Density ◽  
Acoustic Scattering ◽  
Acoustic System ◽  
Counting Method ◽  
Nemopilema Nomurai ◽  
Integration Methods ◽  
Water Columns ◽  
Scattering Strength

In this study, the distribution of Nemopilema nomurai in the waters of Mijo-myeon, Namhae and Gijang-gun, Busan was analyzed; furthermore, echo counting and echo integration methods were used to compare the distribution density. The acoustic system used in the study was a split beam scientific echosounder operating at 38 and 120 kHz (EK-60, Simrad, Norway). Echo counting and echo integration methods were used to determine the density of N. nomurai distributed in the survey areas. The distribution of N. nomurai by water columns, estimated using an echo counting method, was concentrated at approximately 10 m deep in the waters of Mijo, Namhae and 10–50 m deep in the waters of Gijang, Busan; moreover, the distributed depth varied by the surveyed date and time. It was shown that analyzing the acoustic scattering strength of jellyfish obtained from the echo counting method would be more effective for distributional survey of N. nomurai with two frequency system.

Roughness measurement by laser profiler and acoustic scattering strength of a sandy bottom

2014 ◽  
Vol 136 (4) ◽  
pp. 2268-2268
Author(s):  
Nicholas P. Chotiros ◽  
Marcia J. Isakson ◽  
Oscar E. Siliceo ◽  
Paul M. Abkowitz
Keyword(s):  
Acoustic Scattering ◽  
Roughness Measurement ◽  
Sandy Bottom ◽  
Scattering Strength

Acoustic scattering strength of turbulence generated waves in a shallow water flow

2011 ◽  
Vol 130 (4) ◽  
pp. 2436-2436
Author(s):  
V. Kirill Horoshenkov ◽  
Andrew Nichols ◽  
J. Simon Tait ◽  
A. German Maximov
Keyword(s):  
Shallow Water ◽  
Water Flow ◽  
Acoustic Scattering ◽  
Shallow Water Flow ◽  
Scattering Strength

scholarly journals Characteristics of Acoustic Scattering according to Pulsation of the Large Jellyfish Nemopilema nomurai

2010 ◽  
Vol 43 (5) ◽  
pp. 551-556 ◽  
Author(s):  
Eun-A Yoon ◽  
Doo-Jin Hwang ◽  
Miyuki Hirose ◽  
Eun-Ho Kim ◽  
Tohru Mukal ◽  
...  
Keyword(s):  
Acoustic Scattering ◽  
Nemopilema Nomurai

scholarly journals The acoustic characteristics of three jellyfish species: Nemopilema nomurai, Cyanea nozakii, and Aurelia aurita

2009 ◽  
Vol 66 (6) ◽  
pp. 1233-1237 ◽  
Author(s):  
Miyuki Hirose ◽  
Tohru Mukai ◽  
Doojin Hwang ◽  
Kohji Iida
Keyword(s):  
Sound Speed ◽  
Acoustic Scattering ◽  
Aurelia Aurita ◽  
Target Strength ◽  
Bell Diameter ◽  
Nemopilema Nomurai ◽  
Acoustic Characteristics ◽  
Diameter Range ◽  
Jellyfish Species ◽  
Density Methods

Abstract Hirose, M., Mukai, T., Hwang, D., and Iida, K. 2009. The acoustic characteristics of three jellyfish species: Nemopilema nomurai, Cyanea nozakii, and Aurelia aurita. – ICES Journal of Marine Science, 66: 1233–1237. Reports about jellyfish damaging nets and reducing fish catches are increasing, and data on the abundance and distribution of various jellyfish species are needed to forecast where and when their blooms will happen. Acoustic techniques can be used to obtain this information if the acoustic characteristics of the targets are known. This is a study of acoustic scattering from three jellyfish species: Nemopilema nomurai (order Rhizostomeae), Cyanea nozakii (Semaeostomeae), and Aurelia aurita (Semaeostomeae). Target strength (TS) at 38, 120, and 200 kHz, specific density, and sound speed were measured with live specimens. Specific densities were measured using the displacement–volume–weight and the dual-density methods. The sound speeds were estimated using the time-of-flight method. The reduced TS (RTS), i.e. the TS normalized by bell area, was smaller for N. nomurai (bell diameter range 19–38 cm) than for C. nozakii (bell diameter range 30–40 cm), and the differences in RTS between the species were 17.8, 12.6, and 5.8 dB at 38, 120, and 200 kHz, respectively. The respective sound-speed contrast h and density contrast g were 1.0008 ± 0.009 (mean ± s.d.) and 1.004 ± 0.015 for N. nomurai; 1.038 and 1.073 for one C. nozakii; and 1.0001 ± 0.025 and 0.989 ± 0.019 for A. aurita.

scholarly journals Estimates of acoustic target strength for giant jellyfish Nemopilema nomurai Kishinouye in the coastal Northwest Pacific

2013 ◽  
Vol 71 (3) ◽  
pp. 597-603 ◽  
Author(s):  
Donhyug Kang ◽  
Jusam Park ◽  
Seom-Kyu Jung ◽  
Sungho Cho
Keyword(s):  
Acoustic Scattering ◽  
Ex Situ ◽  
Target Strength ◽  
Northwest Pacific ◽  
Bell Diameter ◽  
Least Squares Regression ◽  
Acoustic Measurements ◽  
Nemopilema Nomurai ◽  
Acoustic Target ◽  
Giant Jellyfish

Abstract Acoustic target strength (TS) measurements were made of ex situ giant jellyfish Nemopilema nomurai Kishinouye at 38 and 120 kHz. These TS data may be useful for developing acoustic scattering models, and surveying giant jellyfish distributions and biomasses. Each jellyfish was tethered in seawater using a monofilament line that vertically penetrated its bell's centre. During the acoustic measurements, an underwater video camera was used to continuously monitor the jellyfish's behaviour. Acoustic measurements were made using split-beam transducers. TS measurements were made of 27 individual jellyfish, but data were analysed for 23 specimens (bell diameter in air, Dair = 21–65 cm) at 38 kHz, and 19 specimens (Dair = 21–46 cm) at 120 kHz, respectively. Least-squares regression fits of TS vs. log(Dair) were TS38kHz = 20•log10Dair–82.7 (r = 0.76) and TS120kHz = 20•log10Dair–86.7 (r = 0.79). The mean TS values at 38 and 120 kHz, using the average Dair = 40.3 cm and 35.5 cm, respectively, were −50.6 and −55.7 dB. The reduced TS, a function of the ratio of Dair to wavelength (λ), was RTS(Dair/λ) = −6.1•log10(Dair/λ) –36.1 (r = 0.51). These RTS values decreased with increasing Dair/λ. Symbiotic medusa shrimp (Latreutes anoplonyx Kemp) contributed negligible bias to our TS measurements of giant jellyfish. These ex situ TS measurements may be used in acoustic surveys to estimate the distributions and biomasses of N. nomurai.

scholarly journals Comparisons of day-time and night-time hydroacoustic surveys in temperate lakes

2020 ◽  
Vol 33 ◽  
pp. 9
Author(s):  
Michaël Girard ◽  
Chloé Goulon ◽  
Anne Tessier ◽  
Pascal Vonlanthen ◽  
Jean Guillard
Keyword(s):  
Acoustic Scattering ◽  
Target Strength ◽  
Fish Stock ◽  
Size Estimation ◽  
Temperate Lakes ◽  
Night Time ◽  
Fish Size ◽  
Schooling Behaviour ◽  
Scattering Strength ◽  
Lower Depth

In recent years, due to an increased need for non-intrusive sampling techniques, hydroacoustics has attracted attention in fishery science and management. Efforts to promote standardisation are increasing the accuracy, efficiency, and comparability of this method. The European Water Framework Directive and the Standard Operating Procedures for Fisheries Hydroacoustic Surveys in North American Great Lakes has recommended that surveys be conducted at night. At night, fish usually disperse in the water column, thus allowing for single echo detection and subsequent accurate fish size estimation, while day-time schooling behaviour hampers the estimation of fish size. However, sampling during the day would often be safer and cheaper. This study analyses how fisheries hydroacoustic results differ between day-time and night-time surveys, using data from 14 natural temperate lakes of various size. Data collected during the day and night at two depth layers linked to thermal stratification were compared in terms of acoustic scattering strength, target strength, and biomass estimates. The results showed a significant correlation between day-time and night-time estimates, though biomass in the upper layer was biased for day-time surveys, mainly due to incorrect fish size estimates resulting from rare single echo detections and schooling behaviour. Biomass estimates for the lower depth layer did not significantly differ between the two diel periods. Thus, this study confirms that hydroacoustic sampling in temperate lakes should be performed at night for accurate fish stock biomass estimates.

Measurements of acoustic volume backscattering in the Indian and Southern Oceans

1981 ◽  
Vol 32 (6) ◽  
pp. 855 ◽  
Author(s):  
M Hall
Keyword(s):  
Indian Ocean ◽  
Acoustic Scattering ◽  
Average Depth ◽  
Night Time ◽  
Average Mass ◽  
Average Abundance ◽  
The Indian Ocean ◽  
Scattering Strength ◽  
Great Australian Bight ◽  
Good Agreement

Volume backscattering strengths have been measured at several positions in the Indian Ocean and the Southern Ocean (across the Great Australian Bight). The positions in the Indian Ocean varied from the vicinity of the Equator to a station off the coast of Western Australia near Fremantle. The backscattering strengths have been analysed at frequencies in third-octave steps from 2.5 to 20 kHz. The average daytime scattering strengths at the Equator and in the Bight are similar and range from around - 87 dB re m-1 at 2.5 kHz to between -75 and -70 dB re m-1 at 20 kHz. At night, the average scattering strengths in the Bight increase from about -75 dB re m-1 at 2.5 kHz to about -70 dB re m-1 at 20 kHz, whereas at the Equator the results increase from about -82 dB re m-1 at 2.5 kHz to -64 dB re m-1 at 20 kHz. Deep scattering layers (DSL) were observed both in the Bight and at the Equator. The DSL in the Bight had a resonance frequency of 4 kHz and the average depth of the bottom of the layer was 950 m. From the acoustic scattering strength. it is inferred that the average population density of the fish in the layer is 10-3 m-3, and that the average mass of the fishes is around 40 g. The DSL at the Equator had a flat frequency response at frequencies above 10 kHz (there was no peak in the spectrum) and the average depth of the layer was about 500 m. The average abundance of the scatterers in the layer is inferred to be of the order of 5 × 10-3 m-3. The backscattering strengths measured in the Great Australian Bight have been compared with predictions based on concurrent net hauls that were conducted to depths of 50 and 100 m. Good agreement occurs only at the higher frequencies and at night-time when most of the organisms are near the surface.

Effects of Weakly Nonlinear Waves on Acoustic Scattering from the Ocean Surface

2021 ◽  
pp. 2150007
Author(s):  
Runze Xue ◽  
Rui Duan ◽  
Yuanliang Ma ◽  
Kunde Yang
Keyword(s):  
Nonlinear Waves ◽  
Grazing Angle ◽  
Acoustic Scattering ◽  
Ocean Waves ◽  
Nonlinear Phenomenon ◽  
Weakly Nonlinear ◽  
Bistatic Scattering ◽  
Weakly Nonlinear Waves ◽  
Scattering Strength ◽  
The Impact

The elevation of ocean waves is always modeled in linear theory as a superposition of the sinusoidal components with crests and troughs of identical heights. However, under some circumstances, the wave amplitude is outside the linear range and presents as a weakly nonlinear asymmetrical waveform with sharper crests and shallower troughs. We studied the impact of the weakly nonlinear effect of ocean waves in deep and intermediate waters on acoustic scattering from the surface of the ocean using two rough surface models with fractal geometry and power law spectral behavior in the equilibrium range. The classic Weierstrass–Mandelbrot function was used to model the linear waves and a new fractal function, the fractional Weierstrass function developed in studies of electromagnetism, was used to model the weakly nonlinear waves. We evaluated these two models using the Pierson–Moskowitz spectrum and the incident wavelength. The bistatic scattering strength was obtained via a numerical method based on the “exact” solution of the integral equation. The weakly nonlinear phenomenon led to a very small reduction in the narrow area around the specular reflection angle and a small increase in the remaining wide area, including the backpropagation area with a scattering angle [Formula: see text]. The differences in backscattering strength between the two models were similar to the bistatic scattering strength in the backpropagation area and did not depend on the incident grazing angle.

A Tape Striation Counting Method for Determining Fundamental Frequency

1979 ◽  
Vol 10 (4) ◽  
pp. 246-248 ◽  
Author(s):  
Peter B. Mueller ◽  
Marla Adams ◽  
Jean Baehr-Rouse ◽  
Debbie Boos
Keyword(s):  
Fundamental Frequency ◽  
Counting Method ◽  
Male And Female ◽  
Fundamental Frequencies ◽  
Counting Procedure ◽  
Female Subjects

Mean fundamental frequencies of male and female subjects obtained with FLORIDA I and a tape striation counting procedure were compared. The fundamental frequencies obtained with these two methods were similar and it appears that the tape striation counting procedure is a viable, simple, and inexpensive alternative to more costly and complicated procedures and instrumentation.

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