Acoustic backscattering by Hawaiian lutjanid snappers. I. Target strength and swimbladder characteristics

2003 ◽  
Vol 114 (5) ◽  
pp. 2757 ◽  
Author(s):  
Kelly J. Benoit-Bird ◽  
Whitlow W. L. Au ◽  
Christopher D. Kelley
Keyword(s):  
Target Strength ◽  
Acoustic Backscattering

Analisis Akustik Target Strength Penyu Hijau (Chelonia Mydas) Melalui Pengukuran Secara Terkontrol Pada Frekuensi 200 kHz

2021 ◽  
Vol 3 (2) ◽  
pp. 94-108
Author(s):  
Teddy Julyansyah ◽  
Deddy Bakhtiar ◽  
Ari Anggoro
Keyword(s):  
Green Turtle ◽  
Population Decline ◽  
Chelonia Mydas ◽  
Total Body Length ◽  
Acoustic Method ◽  
Target Strength ◽  
Acoustic Backscattering ◽  
Total Length ◽  
In Captivity ◽  
Total Body

ABSTRACT Turtles are reptiles that live in the sea and are able to migrate over long distances along the Indian Ocean, Pacific Ocean and Southeast Asia. Currently the number of turtle populations in nature has greatly decreased. This population decline is caused by natural factors and human activities that endanger the population directly or indirectly. At this time the tagging set technique (ID tag code) is a method that is often used to detect the presence of turtles by attaching tags to female turtles who are landing to lay eggs on the beach or while in captivity or the discovery of the mother turtle by fishermen. One other method that can be used to detect the presence of turtles is to use the acoustic method. The purpose of this study was to analyze the characteristics of the acoustic backscattering energy of the green turtle (Chelonia mydes) and to analyze the relationship between target strength and total body length of the green turtle (Chelonia mydas). This research was conducted in the Tapak Paderi waters pond, Bengkulu City, in August-October 2020. The average target strength (TS) value for green turtles was -48.07 dB. Based on the regression equation, the value of determination (R2) obtained is 0.78. Where this value shows that the total length of the green turtle has an effect of 78% on the average target strength (TS) value, while for 22% it is caused by other factors such as body shape, environmental factors and other factors. Based on the ANOVA test, it can be concluded that there is a relationship between the total length and the value of the target strength (TS) on the green turtle or the value of the total length has an influence on the value of the target strength (TS) on the green turtle.  

Convergence of Acoustic, Optical, and Net-Catch Estimates of Euphausiid Abundance: Use of Artificial Light to Reduce Net

1993 ◽  
Vol 50 (2) ◽  
pp. 334-346 ◽  
Author(s):  
D. Sameoto ◽  
N. Cochrane ◽  
A. Herman
Keyword(s):  
Target Strength ◽  
Sampling System ◽  
Remotely Operated Vehicle ◽  
Acoustic Backscattering ◽  
Video Cameras ◽  
Acoustic Target ◽  
Avoidance Reactions ◽  
Theoretical Scattering ◽  
System Operating

Euphausiid concentrations in the Scotian Shelf basins were sampled with BIONESS, a multinet sampling system, and quantitatively assessed simultaneously with an in situ optical zooplankton counter (OPC) mounted on BIONESS and with an acoustic backscattering system operating simultaneously at 50, 122, and 200 kHz. Supplementary observations were made with vertically dropped video cameras and video and 35-mm frame cameras mounted on a remotely operated vehicle (ROV). The use of a light source on BIONESS during sampling increased the catch of euphausiids by 10–20 times by reducing active avoidance reactions to the net. Consequently, conventional net sampling has greatly underestimated euphausiid concentrations, a conclusion suggested by previous acoustic measurements. Experimental acoustic target strengths for 28-mm euphausiids averaged −77.5, −73.4, and −68.4 dB at 50, 122, and 200 kHz, respectively, using measured Sv levels and assuming 100% net sampling efficiency. Theoretical scattering models based on randomly oriented cylinders require the euphausiids to be oriented within about 5° of the horizontal to approximate both the experimentally observed target strength amplitudes and their frequency dependence. Acoustic interpretation has been enhanced by incorporation of transducer sensitivity versus temperature corrections and modeling techniques that allow for finite transducer beam widths.

scholarly journals Estimating gear efficiency in a combined acoustic and trawl survey, with reference to the spatial distribution of demersal fish

2009 ◽  
Vol 67 (4) ◽  
pp. 668-676 ◽  
Author(s):  
Mathieu Doray ◽  
Stéphanie Mahévas ◽  
Verena M. Trenkel
Keyword(s):  
Spatial Distribution ◽  
Demersal Fish ◽  
Target Strength ◽  
Fish Length ◽  
Trawl Survey ◽  
Acoustic Backscattering ◽  
Scattering Coefficients ◽  
Fishing Vessels ◽  
Gear Efficiency ◽  
The Mean

Abstract Doray, M., Mahévas, S., and Trenkel, V. M. 2010. Estimating gear efficiency in a combined acoustic and trawl survey, with reference to the spatial distribution of demersal fish. – ICES Journal of Marine Science, 67: 668–676. Few analyses have been performed to estimate the efficiency of trawls targeting demersal fish using the ratio of catches and acoustic densities. In summer 2006, acoustic and fishing data were collected simultaneously over 3 d by three fishing vessels equipped with identical pelagic trawls in the Bay of Biscay. Variography identified moderate spatial autocorrelation in the acoustic backscatter at a mean scale of 3 km, a scale slightly smaller than the mean haul length (3.5 km), indicating that fish horizontal availability did not influence trawl efficiency. Acoustic backscattering densities expressed as nautical area scattering coefficients (NASCs) recorded in the trawled layer were compared with equivalent NASC (ENASC) values calculated from the species composition in the trawl, fish-length structure, and available relationships between target strength and fish length. Estimates of trawl efficiency for hake-dominated trawls were computed as the slopes of the relationships ENASC = 0.008 NASC and ENASC = 0.18 NASC0.31 for trawls made by day and night, respectively. For the whole demersal community, the relationships were ENASC = 0.022 NASC and ENASC = 0.17 NASC0.33 for trawls made by day and night, respectively.

scholarly journals On the target strength of Baltic clupeids

2009 ◽  
Vol 66 (6) ◽  
pp. 1184-1190 ◽  
Author(s):  
Sascha M. M. Fässler ◽  
Natalia Gorska
Keyword(s):  
Target Strength ◽  
Biomass Estimation ◽  
Spatial And Temporal Variability ◽  
Important Species ◽  
Acoustic Frequency ◽  
Acoustic Backscattering ◽  
Baltic Herring ◽  
Fish Morphology ◽  
The Baltic ◽  
Relationship Of

Abstract Fässler, S. M. M., and Gorska, N. 2009. On the target strength of Baltic clupeids. – ICES Journal of Marine Science, 66: 1184–1190. The acoustic backscattering of Baltic clupeids, herring and sprat, is explored to improve biomass estimation of these ecologically and commercially important species. Modelling approaches that account for the complexity of fish morphology are used to compute the mean backscattering cross section. The input data for modelling are based on X-ray radiographs of Baltic herring and sprat. The backscatter sensitivity to fish morphology and to other biological (fat content), acoustic (frequency), behavioural (orientation pattern), and environmental (depth and salinity) parameters is also analysed. The effect of various parameters on the TS–L relationship of Baltic clupeids is studied, and the possibility of using the same TS–L relationships for Baltic herring and sprat is discussed. The results improve the understanding of the spatial and temporal variability of the measured target strength of clupeids in the Baltic Sea.

Acoustic characterization of Mysis relicta at multiple frequencies

2008 ◽  
Vol 65 (12) ◽  
pp. 2769-2779 ◽  
Author(s):  
Lars G. Rudstam ◽  
Frank R. Knudsen ◽  
Helge Balk ◽  
Gideon Gal ◽  
Brent T. Boscarino ◽  
...  
Keyword(s):  
Average Length ◽  
Target Strength ◽  
Mysis Relicta ◽  
Detection Range ◽  
Acoustic Backscattering ◽  
Acoustic Data ◽  
Acoustic Characterization ◽  
Lower Maximum ◽  
Multiple Frequencies

We measured acoustic backscattering from Mysis relicta , a common invertebrate in northern lakes, using five frequencies (38, 120, 200, 430, and 710 kHz). Acoustic backscattering from mysids was highest at 430 kHz and lowest at 38 kHz (19 dB lower). Maximum difference between the four other frequencies was 5.2 dB. Mysid target strength (TS) ranged from –80.1 dB at 430 kHz to –99.4 dB at 38 kHz (12 mm average length, range 5–21 mm). A theoretical scattering model (Stanton’s fluid-like, bent-cylinder model) predicted TS within 0.3–1.9 dB of observed TS for the different frequencies. The detection range was lowest at 38 and 710 kHz and greatest at 120 and 200 kHz. Fish were common above the mysid layer and produced higher acoustic backscattering at 38 kHz than at the other frequencies. A combination of 38 kHz and 120 or 200 kHz provides a strong contrast between mysid and fish acoustic backscattering that would help separate these groups using acoustic data.

Response of Biological Acoustic Backscattering to Ships' Lights

1985 ◽  
Vol 42 (9) ◽  
pp. 1535-1543 ◽  
Author(s):  
D. Sameoto ◽  
N. A. Cochrane ◽  
A. W. Herman
Keyword(s):  
Nova Scotia ◽  
Continental Shelf ◽  
Sea Surface ◽  
Target Strength ◽  
Acoustic Response ◽  
Strong Response ◽  
Acoustic Backscattering ◽  
Back Scattering ◽  
Biological Sampling ◽  
Scattering Strength

The response of zooplankton (copepods and euphausiids) and micronekton (myctophids) to ships' lights was quantitatively assessed in terms of the acoustic backscattering from these organisms under controlled sea surface illumination. Two frequencies, 51 and 198 kHz, were utilized. No acoustic response to light on stations off the edge of the Nova Scotia continental shelf was found but a strong response on the shelf was observed. The response at both frequencies consisted of a nearly instantaneous drop in volume back-scattering strength by as much as 20 dB in the top 60 m. Biological sampling tentatively suggested that the organisms responsible were euphausiids and that a sudden geometric reorientation when the light was turned on resulted in a drop in their target strength.

Multiple-Frequency Acoustic Backscattering and Zooplankton Aggregations in the Inner Scotian Shelf Basins

1991 ◽  
Vol 48 (3) ◽  
pp. 340-355 ◽  
Author(s):  
N. A. Cochrane ◽  
D. Sameoto ◽  
A. W. Herman ◽  
J. Neilson
Keyword(s):  
Target Strength ◽  
Scotian Shelf ◽  
Migration Patterns ◽  
Acoustic Backscattering ◽  
Large Populations ◽  
Order Of Magnitude ◽  
Silver Hake ◽  
Merluccius Bilinearis ◽  
Domain Dependence

Acoustic backscatter observations at 12, 50, and 200 kHz in the inner Scotian Shelf basins reveal large populations of silver hake (Merluccius bilinearis) and its principal prey, the euphausiid Meganyctiphanes norvegica. Multichannel sonar colour imagery facilitates separation of fish from euphausiids and delineation of their separate diurnal migration patterns. Silver hake acoustic abundances are consistent with midwater trawl sampling. Acoustic column densities for mature M. norvegica of approximately 1000/m2 exceed net sampling column densities by over 1 order of magnitude indicating strong net avoidance. Numerical simulation of euphausiid backscattering using a fluid cylinder model and natural distribution of scatterer orientations yields an approximate 20 log L target strength length dependence and little frequency domain dependence in the "geometric" scattering regime. Quantitative interpretation of euphausiid scattering in situ must account for randomness in their orientations.

scholarly journals Modelling the acoustic effect of swimbladder compression in herring

2003 ◽  
Vol 60 (3) ◽  
pp. 548-554 ◽  
Author(s):  
Natalia Gorska ◽  
Egil Ona
Keyword(s):  
Orientation Distribution ◽  
Target Strength ◽  
Acoustic Effect ◽  
Acoustic Backscattering ◽  
Cylinder Model ◽  
Acoustic Surveys ◽  
The Mean ◽  
Theoretical Results

Abstract Obtaining accurate data on fish target strength (TS) is important when determining the quality of the results from acoustic surveys. However, this requires an improved understanding of both behavioural and environmental influences on the acoustic backscattering by fish. It is well known that the increased pressure with depth compresses the swimbladder of herring, and it has been confirmed by in situ measurements that the TS of adult herring (30–34 cm) is 3–5 dB weaker at 300 m than that of fish close to the surface. Understanding exactly how swimbladder compression may influence herring TS is, therefore, of great interest, and is the main motivation behind this study. Taking account of swimbladder volume changes with depth, we obtained analytical solutions using the Modal-Based, Deformed-Cylinder Model (MB-DCM). The mean-backscattering cross-section is then computed with selected orientation patterns, length distributions, and contrast parameters. The depth-dependence of TS at different acoustic frequencies has been studied. We conducted a sensitivity analysis to show how TS is dependent on the contraction rates of the bladder dimensions and on the fish-orientation distribution. Our theoretical results are compared with TS measured at 38 kHz.

Physiological factors causing natural variations in acoustic target strength of fish

1990 ◽  
Vol 70 (1) ◽  
pp. 107-127 ◽  
Author(s):  
E. Ona
Keyword(s):  
Seasonal Variations ◽  
Major Part ◽  
Gonad Development ◽  
Target Strength ◽  
Main Function ◽  
Normal Appearance ◽  
Physiological Factors ◽  
Acoustic Backscattering ◽  
Acoustic Target ◽  
Natural Variations

The swimbladder is recognized as responsible for a major part of the acoustic backscattering from fish. In most fishes it has the function of a buoyancy regulator but in others its main function is rather unclear. Based on methods for exact mapping of the swimbladder shape, observations of deviations from normal appearance and shape are discussed in relation to possible effects on target strength. Evidence for both periodic variations, as from uncompensated vertical migrations, and seasonal variations, caused by the fat cycle and gonad development, are presented.

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