Sound extinction by fish schools: forward scattering theory and data analysis.
10 Dec 2013-Journal of the Acoustical Society of America (Acoustical Society of America)-Vol. 137, Iss: 2, pp 539-555
TL;DR: The analysis shows that using forward scattering leads to significantly larger estimates of fish abundance than previous analysis based upon back scattering approaches.
Abstract: A model used previously to study collective back scattering from fish schools [Feuillade et al., J. Acoust. Soc. Am. 99(1), 196–208 (1996)], is used to analyze the forward scattering properties of these objects. There is an essential physical difference between back and forward scattering from fish schools. Strong frequency dependent interference effects, which affect the back scattered field amplitude, are absent in the forward scattering case. This is critically important for data analysis. There is interest in using back scattering and transmission data from fish schools to study their size, the species and abundance of fish, and fish behavior. Transmission data can be processed to determine the extinction of the field by a school. The extinction of sound depends on the forward scattering characteristics of the school, and data inversion to provide information about the fish should be based upon a forward scattering paradigm. Results are presented of an analysis of transmission data obtained in September 1995 during an experiment performed in the Gulf of Lion in the Mediterranean Sea [Diachok, J. Acoust. Soc. Am. 105(4), 2107–2128 (1999)]. The analysis shows that using forward scattering leads to significantly larger estimates of fish abundance than previous analysis based upon back scattering approaches.
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TL;DR: It is experimentally and theoretically found that attenuation can be significant when the sensing frequency is near the resonance frequency of the shoaling fish and common heuristic approaches that employ free space scattering assumptions for attenuation from fish groups can lead to significant errors for applications involving long-range waveguide propagation and scattering.
Abstract: Acoustics is the primary means of long-range and wide-area sensing in the ocean due to the severe attenuation of electromagnetic waves in seawater. While it is known that densely packed fish groups can attenuate acoustic signals during long-range propagation in an ocean waveguide, previous experimental demonstrations have been restricted to single line transect measurements of either transmission or backscatter and have not directly investigated wide-area sensing and communication issues. Here we experimentally show with wide-area sensing over 360° in the horizontal and ranges spanning many tens of kilometers that a single large fish shoal can significantly occlude acoustic sensing over entire sectors spanning more than 30° with corresponding decreases in detection ranges by roughly an order of magnitude. Such blockages can comprise significant impediments to underwater acoustic remote sensing and surveillance of underwater vehicles, marine life and geophysical phenomena as well as underwater communication. This makes it important to understand the relevant mechanisms and accurately predict attenuation from fish in long-range underwater acoustic sensing and communication. To do so, we apply an analytical theory derived from first principles for acoustic propagation and scattering through inhomogeneities in an ocean waveguide to model propagation through fish shoals. In previous experiments, either the attenuation from fish in the shoal or the scattering cross sections of fish in the shoal were measured but not both, making it impossible to directly confirm a theoretical prediction on attenuation through the shoal. Here, both measurements have been made and they experimentally confirm the waveguide theory presented. We find experimentally and theoretically that attenuation can be significant when the sensing frequency is near the resonance frequency of the shoaling fish. Negligible attenuation was observed in previous low-frequency ocean acoustic waveguide remote sensing (OAWRS) experiments because the sensing frequency was sufficiently far from the swimbladder resonance peak of the shoaling fish or the packing densities of the fish shoals were not sufficiently high. We show that common heuristic approaches that employ free space scattering assumptions for attenuation from fish groups can lead to significant errors for applications involving long-range waveguide propagation and scattering.
10 citations
Dissertation•
01 Jan 2017
TL;DR: In this article, the authors propose a method to solve the problem of "uniformity" and "uncertainty" in the context of health care, and propose a solution.
Abstract: xxvi
7 citations
Cites background or methods or result from "Sound extinction by fish schools: f..."
...In Chapter 5, the Foldy (1945) equations are used along with the Love (1978) model, like Raveau and Feuillade (2015)....
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...When testing this model with different swimbladder bearing fish, Love (1978) noted that the damping due to thermal effects is negligible (Love 1978, Raveau and Feuillade 2015)....
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...The form of the fish model equations considered here are similar to that of Raveau and Feuillade (2015)....
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...In Chapter 5 of this thesis, omnidirectional point scatterers are considered with scattering and extinction cross sections which are that of the particular fish species using the forms of the Love (1978) model in Raveau and Feuillade (2015)....
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...…for the frequencies considered, in Alfaro et al. (2015) to analyze the statistics of the target strength of dynamic unspecified fish schools, and in Raveau and Feuillade (2015) to study the forward scattering behavior from collections of fish, particularly sardines (kas ~ 0.04 (Machias and…...
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TL;DR: In this paper , an efficient method is developed to numerically compute the map of the density of scattering resonances in the complex plane of the wavenumber without finding them one by one.
Abstract: The multiple scattering model of a quantum particle in a random Lorentz gas consisting of fixed point scatterers is considered in arbitrary dimension. An efficient method is developed to numerically compute the map of the density of scattering resonances in the complex plane of the wavenumber without finding them one by one. The method is applied to two collision models for the individual scatterers, namely a resonant model, and a non-resonant hard-sphere model. The results obtained with the former are compared to the literature. In particular, the spiral arms surrounding the single-scatterer resonance are identified as proximity resonances. Moreover, the hard-sphere model is used to reveal previously unknown structures in the resonance density. Finally, it is shown how Anderson localization affects the distribution of resonance widths, especially in the one-dimensional case.
5 citations
TL;DR: A theoretical comparison of the models for idealized spherical schools shows good agreement over the entire resonance region in the forward direction, where interference interactions have a minimal effect, and indicates a method for estimating fish abundance.
Abstract: The effective medium method is used to investigate resonance scattering from schools of fish with gas-filled swim bladders, as a function of frequency and azimuth. Calculations are also performed with a coupled differential equation model, which incorporates both multiple scattering between fish and wave interference interactions of their scattered fields [Feuillade, Nero, and Love, J. Acoust. Soc. Am. 99, 196–208 (1996)]. A theoretical comparison of the models for idealized spherical schools shows good agreement over the entire resonance region in the forward direction, where interference interactions have a minimal effect. Good agreement is also seen in back scattering at low frequencies, where the wavelength λ≥4s, and s is the average nearest neighbor fish separation. If λ<4s, the models diverge in back scattering, and the effective medium method fails. This can be critically important when migrations of schools to deeper water cause the collective resonance frequency to increase. Multiple scattering i...
5 citations
TL;DR: In many ways, finding fish, especially in large quantities, was a “shot in the dark,” but this started to change when fisheries biologists started to apply acoustics to the hunt for fishes as discussed by the authors.
Abstract: Introduction How does one find fishes in the sea? For millennia, catching fish has depended on luck for a fisherman out for a day of recreation and both luck and knowledge of fish behavior and ecological preferences for those seeking larger catches. Still, in many ways, finding fish, especially in large quantities, was a “shot in the dark.” However, this started to change when fisheries biologists started to apply acoustics to the hunt for fishes. The various approaches that have been used and that continue to evolve now enable fishers not only to find large groups of fish more efficiently and effectively but also to enable fishery biologists to quantify the number of fish in areas of interest, their migration patterns, and how their numbers evolve over time as well as other aspects of their behavior.
3 citations
Cites background from "Sound extinction by fish schools: f..."
...…the separation between fish is less than two fish lengths (Pitcher and Parrish,1993), then the close proximity between fish dampens the resonances of each fish and causes the school to act as a “bubble cloud” that resonates at a lower frequency (F; Diachok, 1999; Raveneau and Feuillade, 2015)....
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...The diameters of the symbols are proportional to the magnitudes of the attenuation coefficients at f0 and F. Theoretical calculations of F are from Raveneau and Feuillade, 2015....
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...biological attenuation between night and day is driven primarily by the difference in the separation between fish in dispersed and school modes and, to a lesser extent, by the difference in the effective radius of swim bladders (Diachok, 1999; Raveneau and Feuillade, 2015)....
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...A more sophisticated theory, however, is required to infer the number densities when fish are in close proximity in schools (Raveneau and Feuillade, 2015)....
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...The difference in biological attenuation between night and day is driven primarily by the difference in the separation between fish in dispersed and school modes and, to a lesser extent, by the difference in the effective radius of swim bladders (Diachok, 1999; Raveneau and Feuillade, 2015)....
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References
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Book•
01 Jan 1978
TL;DR: This IEEE Classic Reissue presents a unified introduction to the fundamental theories and applications of wave propagation and scattering in random media and is expressly designed for engineers and scientists who have an interest in optical, microwave, or acoustic wave propagate and scattering.
Abstract: A volume in the IEEE/OUP Series on Electromagnetic Wave Theory Donald G. Dudley, Series Editor This IEEE Classic Reissue presents a unified introduction to the fundamental theories and applications of wave propagation and scattering in random media. Now for the first time, the two volumes of Wave Propagation and Scattering in Random Media previously published by Academic Press in 1978 are combined into one comprehensive volume. This book presents a clear picture of how waves interact with the atmosphere, terrain, ocean, turbulence, aerosols, rain, snow, biological tissues, composite material, and other media. The theories presented will enable you to solve a variety of problems relating to clutter, interference, imaging, object detection, and communication theory for various media. This book is expressly designed for engineers and scientists who have an interest in optical, microwave, or acoustic wave propagation and scattering. Topics covered include:
5,877 citations
01 Jan 1986
TL;DR: Predators and food are the keys to understanding fish shoals; synchronised co-operation defeats predators, and optimal food gathering in shoals reflects a shifting balance between joining, competing in, or leaving the group.
Abstract: Predators and food are the keys to understanding fish shoals; synchronised co-operation defeats predators, and optimal food gathering in shoals reflects a shifting balance between joining, competing in, or leaving the group In the wild, predators may arrive while shoaling fish are feeding, and so vigilance is a crucial behaviour Once detected, predator defence takes precedence over feeding, since an animal’s life is worth more than today’s dinner
1,200 citations
1,126 citations
TL;DR: In this article, a theoretical discussion on the fundamental processes by which pulsating gas bubbles in liquids dissipate their energy is presented, where the amplitude of the volume pulsations are assumed to be sufficiently small that the pulsations may be described by linear equations.
Abstract: A theoretical discussion is presented on the fundamental processes by which pulsating gas bubbles in liquids dissipate their energy. The survey is limited to the case where the amplitude of the volume pulsations are assumed to be sufficiently small that the pulsations may be described by linear equations. A portion of the energy of the bubble system is lost by the radiation of spherical sound waves, a part is lost by heat conduction due to the polytropic compressions and expansions of the enclosed gas, and a portion is lost by viscous dissipation attributed to viscous forces acting at the gas‐liquid interface. A survey is made of the procedures for measuring the resonant damping constant as described in the methods of successive oscillations, width of the resonance response, standing‐wave ratios, and resonance absorption. Experimental results verify that the damping at resonance is due to thermal and radiation, and possibly viscous damping.
402 citations
TL;DR: Two methods are described for measuring the three-dimensional co-ordinates of the individual fish in a school photographed from above using a double-prism device and the Shadow Method.
130 citations