Acoustic scattering properties of juvenile jack mackerel <i>Trachurus japonicus</i> based on a scattering model and <i>ex situ</i> target strength measurements

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.

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Verification and application of Target Strength for Japanese anchovy (Engraulis japonicas) by theoretical acoustic scattering model

Journal of the Korean society of Fisheries Technology ◽

10.3796/ksft.2012.48.4.487 ◽

2012 ◽

Vol 48 (4) ◽

pp. 487-494 ◽

Cited By ~ 1

Author(s):

Kangseok Hwang ◽

Kyounghoon Lee ◽

Bo-Kyu Hwang

Keyword(s):

Acoustic Scattering ◽

Target Strength ◽

Japanese Anchovy ◽

Scattering Model

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Measurements of acoustic-scattering spectra from the whole and parts of Atlantic mackerel

ICES Journal of Marine Science ◽

10.1093/icesjms/fsp087 ◽

2009 ◽

Vol 66 (6) ◽

pp. 1169-1175 ◽

Cited By ~ 13

Author(s):

Tonje Lexau Nesse ◽

Halvor Hobæk ◽

Rolf J. Korneliussen

Keyword(s):

Frequency Response ◽

Acoustic Scattering ◽

Ex Situ ◽

Target Strength ◽

Model Parameters ◽

Acoustic Frequency ◽

Atlantic Mackerel ◽

Scattering Spectra ◽

Laboratory Tank

Abstract Nesse, T. L., Hobæk, H., and Korneliussen, R. J. 2009. Measurements of acoustic-scattering spectra from the whole and parts of Atlantic mackerel. – ICES Journal of Marine Science, 66: 1169–1175. Atlantic mackerel (Scomber scombrus) are weak sound scatterers compared with fish that have swimbladders. Accurate acoustic estimates of mackerel abundance require estimates of target strength. Different parts of mackerel may dominate the backscattering spectra. Mackerel schools are acoustically recognized mainly by backscatter four times stronger at 200 kHz than at 38 kHz. Simulations have established that backscatter from only the flesh and the backbone could explain this frequency response, although there are uncertainties in the model parameters and simplifications. In this paper, experiments conducted in a laboratory tank to investigate the complexity of mackerel backscatter are discussed. Acoustic backscatter was measured over the frequency range 65–470 kHz from individual dead mackerel, and their backbones, heads, and skulls. Backscatter from the backbones was measured at several angles of incidence. Grating lobes (Bragg scattering) appeared at different angles, depending on the acoustic frequency and the spacing of the vertebrae. These lobes were evident in backbone backscatter after propagating through the flesh and can be used, in principle, to determine mackerel size acoustically. The frequency response of individual, ex situ Atlantic mackerel estimated from these measurements did not match that from the measurements of in situ mackerel schools. Further investigation is warranted.

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

ICES Journal of Marine Science ◽

10.1093/icesjms/fst182 ◽

2013 ◽

Vol 71 (3) ◽

pp. 597-603 ◽

Cited By ~ 2

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.

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