On Representing the Length Dependence of Acoustic Target Strengths of Fish

1979 ◽  
Vol 36 (12) ◽  
pp. 1490-1496 ◽  
Author(s):  
Kenneth G. Foote
Keyword(s):  
Analysis Of Covariance ◽  
Target Strength ◽  
Fish Length ◽  
Length Dependence ◽  
Dorsal Aspect ◽  
Significance Levels ◽  
Acoustic Target ◽  
Representation Method ◽  
Strength Functions ◽  
Linear Regressions

The problem of representing the length dependence of acoustic target strengths of fish is addressed by studying the legitimacy of merging target strengths that are inhomogeneous in species or frequency. The target strengths are of two kinds: maximum and averaged dorsal aspect target strengths, which are derived from measurements of gadoid target strength functions of three species at two ultrasonic frequencies. The target strengths are expressed variously according to unnormalized, wavelength-normalized and length-normalized schemes. Overall coincidences and coincidences of slopes among simple linear regressions of target strength on fish length, when segregated by target strength type and manner of representation, are investigated through analysis of covariance. Examination of computed significance levels demonstrates that merging of target strengths in species or frequency is generally unjustified and that no one representation method is superior to another in facilitating the merging of such data. The unnormalized representation is to be preferred when merging is justified because of its simplicity and avoidance of the frequency bias inherent in the normalized representations. The hypothesis of scaling of target strengths is refuted. Key words: target strength, regression, covariance analysis, fish abundance estimation

Estimation of Fish Length from Acoustic Target Strengths

1987 ◽  
Vol 44 (10) ◽  
pp. 1782-1785 ◽  
Author(s):  
U. Buerkle
Keyword(s):  
Gadus Morhua ◽  
Statistical Significance ◽  
Orientation Distribution ◽  
Target Strength ◽  
Fish Length ◽  
Fish Sample ◽  
Length Frequency ◽  
Frequency Structure ◽  
Acoustic Target

I show that fish length distributions calculated from acoustic target strengths of cod (Gadus morhua) are in error when target strength–length relationships are used that do not account for the orientation distribution of the fish. The magnitude and statistical significance of the errors vary with the length frequency structure of the fish sample and are thought to be large enough to question the value of acoustically determined lengths in fish surveys if corrections for fish orientation are not applied.

scholarly journals Estimation of the Coefficients of the Equation of Acoustic Target Strength Based on the Morphology of Coregonus migratorius (Georgi, 1775) Swim Bladder

2020 ◽  
Vol 15 (1) ◽  
pp. 89-98
Author(s):  
P. N. Anoshko ◽  
M. M. Makarov ◽  
S. B. Popov ◽  
A. I. Degtev ◽  
N. N. Denikina ◽  
...  
Keyword(s):  
Acoustic Scattering ◽  
Morphological Characteristics ◽  
Prolate Spheroid ◽  
The Body ◽  
Target Strength ◽  
Fish Length ◽  
Swim Bladder ◽  
Experimental Conditions ◽  
Scattering Model ◽  
Acoustic Target

Aim. The aim of the study was to estimate the coefficients of the equation TSmax=f(SL) considering the characteristics of an acoustic scattering model based on the morphological characteristics of the swim bladder of the Coregonus migratorius (Georgi, 1775). Material and Methods. Ninety‐nine living specimens of C. migratorius served as the study material. For each specimen, the target strength in the cage was measured using an Kongsberg Simrad EY500 echo sounder and the morphology of the swim bladder was studied. Measurements, analysis of images and data were conducted using Image Pro 6.0. Excel and SciLab software resources. Results. We determined the main morphological characteristics of the swim bladder in C. migratorius as well as the correspondence of its dimensions and proportions in relation to the length of the fish’s body. The coefficients of the equation TS=20log(SL)‐60, calculated on the results of the acoustic scattering model of a prolate spheroid, agree well with the coefficients calculated from maximum values obtained in the cage experiment. During the conversion of the coefficients relating to the allometric changes in the length of the swim bladder relative to fish length, the equation TS=23.2log(SL)‐64.4 was obtained. A comparative analysis of the available equations of the target strength for C. migratorius with those obtained in the study was undertaken. Conclusion. The equation obtained on the model of the swim bladder as a prolate spheroid adequately describes the dependence of the maximum values of the target strength on the body length of the C. migratorius and confirms the previously obtained dependence by maximum values of TS in the cage experimental conditions and can serve as a basis for further theoretical studies.

scholarly journals In situ target strength of the Baltic Sea herring and sprat

2004 ◽  
Vol 61 (3) ◽  
pp. 378-382 ◽  
Author(s):  
Tomas Didrikas ◽  
Sture Hansson
Keyword(s):  
Baltic Sea ◽  
Clupea Harengus ◽  
Target Strength ◽  
Fish Length ◽  
The North ◽  
Length Relationship ◽  
Stock Biomass ◽  
Acoustic Target ◽  
The North Sea ◽  
The Baltic

Abstract Using single- and split-beam hydroacoustic equipment (70 and 38 kHz), and gillnet and trawl catches, we derived the relationship TS = 25.5 log10 L − 73.6 (r2=0.95) between acoustic target strength (TS) and fish length (L, cm) for Baltic Sea herring (Clupea harengus membras L.) and sprat (Sprattus sprattus balticus (Schneider)). Fixing the slope to 20, which is a standard practice in hydroacoustics, gave TS = 20 log10 L − 67.8 (r2=0.91). Normally, the fisheries agencies around the Baltic use a TS–length relationship that is based mainly on data from the North Sea and the intercept-value in this equation is 3.4 dB lower than that reported in this paper. This difference corresponds to an approximately twofold difference in assessed stock biomass.

scholarly journals Acoustic Target Strength Measurements for Biomass Estimation of Aquaculture Fish, Redlip Mullet (Chelon haematocheilus)

2018 ◽  
Vol 8 (9) ◽  
pp. 1536 ◽  
Author(s):  
Hansoo Kim ◽  
Donhyug Kang ◽  
Sungho Cho ◽  
Mira Kim ◽  
Jisung Park ◽  
...  
Keyword(s):  
Coastal Waters ◽  
Regression Line ◽  
Constant Term ◽  
Ex Situ ◽  
Target Strength ◽  
Biomass Estimation ◽  
Fish Length ◽  
Least Squares Regression ◽  
Wide Range ◽  
Acoustic Target

Redlip mullet (Chelon haematocheilus) is distributed in coastal waters of the North-Western Pacific Ocean and is a cultured fish in Korea. A hydroacoustic technique constitutes a useful method to assess the biomass and spatial distribution of mullet in sea cages or in coastal waters, and acoustic target strength (TS) information of the target fish is an essential parameter in using this method. In this study, ex situ TS measurements of 16 live mullets were made in an aquaculture sea cage in Korea. The split-beam scientific echo-sounder used for measurements was comprised of 38, 120, 200, and 420 kHz frequencies. An underwater video camera was simultaneously used to observe the mullets’ behavior during the TS measurements. The mullet TS data was analyzed from a wide range of total fish length (FL: 14.3–40.3 cm). As results for all frequencies, the frequency dependence of the mean TS values were relatively low, and the difference in mean TS was within 2.5 dB. When the slope of the least-squares regression line was forced to 20 into the TS equation, the resulting value for the constant term (b20) at each frequency was −67.0 dB, −68.3 dB, −66.3 dB, and −68.5 dB, respectively. The data tended to be frequency dependent. Additionally, the maximum TS appeared between tilt angles of 0° and 10°. These results indicate that TS measurements can be applied to estimate the biomass of the mullet in sea cages or in coastal waters.

scholarly journals Modelling the target strength of Trachurus symmetricus murphyi based on high-resolution swimbladder morphometry using an MRI scanner

2008 ◽  
Vol 65 (9) ◽  
pp. 1751-1761 ◽  
Author(s):  
Héctor Peña ◽  
Kenneth G. Foote
Keyword(s):  
High Resolution ◽  
Three Dimensional ◽  
Dorsal Surface ◽  
Axial Direction ◽  
Target Strength ◽  
Whole Body ◽  
Fish Length ◽  
Acoustic Target ◽  
Total Fish ◽  
Magnetic Resonance Imaging Mri

Abstract Peña, H., and Foote, K. G. 2008. Modelling the target strength of Trachurus symmetricus murphyi based on high-resolution swimbladder morphometry using an MRI scanner. – ICES Journal of Marine Science, 65: 1751–1761. The acoustic target strength (TS) of Chilean jack mackerel (Trachurus symmetricus murphyi) was computed from three-dimensional reconstructions of the swimbladder form. The primary morphometric data were derived from high-resolution images made with a clinical whole-body 3-tesla magnetic resonance imaging (MRI) scanner. The fish were obtained from a commercial purse-seiner operating off Chile during 2003. Transverse MRI sequences of 18 fish were performed with a volumetric pixel 0.5 × 0.5 mm in cross section and 0.7 mm in the axial direction. From each transverse section, the swimbladder contour was traced manually using a digital pen tablet and smoothed using an automatic interpolation routine. The digital contours were used to build a triangular mesh spanning the swimbladder surface. The high-resolution swimbladder models revealed details such as undulations in the dorsal surface of the swimbladder caused by the backbone, and holes where the haemal spines penetrate the posterior end of the swimbladder. The Kirchhoff approximation was used to compute TS as a function of fish orientation at 38 kHz. The mean dorsal-aspect TS was computed for several orientation patterns and regressed on the logarithm of total fish length to derive operationally simple formulae.

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