Target strength estimates of red emperor (<i>Lutjanus sebae</i>) with Bayesian parameter calibration

Gastauer, Sven; Scoulding, Ben; Fässler, S.M.M.; Benden, Daniel P.L.D.; Parsons, Miles

doi:10.1051/alr/2016024

Cited by 9 publications

(3 citation statements)

References 45 publications

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“…Acoustic parameters, such as the density contrast (g) and sound speed contrast (h), were needed in this model. Previous researchers found that fish flesh had g values ranging from ~1.02 to 1.06 and h values from ~1.02 to 1.08 (Love, 1978;Medwin and Clay, 1998;Gastauer et al, 2016). Typical acoustic parameters of fish with a swim bladder, measured using Atlantic cod (Gadus morhua), from literature (Clay and Horne, 1994) were chosen in our model (Table 1), which were also used in the jack mackerel (Trachurus japonicus) TS research performed by Hwang et al (2015).…”

Section: Ts Estimationmentioning

confidence: 99%

Impacts of Morphological Characteristics on Target Strength of Chub Mackerel (Scomber japonicus) in the Northwest Pacific Ocean

et al. 2022

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Chub mackerel (Scomber japonicus) is an important commercial fish in the Northwest Pacific Ocean. Accurate target strength (TS) underpins acoustic stock assessment but the TS of S. japonicus is still poorly understood. In this study, the Kirchhoff-ray mode (KRM) model was used to estimate the TS of S. japonicus and its relationship with sound wave frequency and fish morphology. The results revealed that TS values varied with pitch angle shifts, with the impact on fish scattering strength being greater at higher frequency. This is less important because 38 kHz has been used for the biomass assessment of these fish resources. At frequencies of 38 kHz, 70 kHz, 120 kHz and 200 kHz, TS was greatest at a pitch angle range of -10° to 0°, which was related to the angle of the swim bladder tilt. There were almost no differences between TS estimated using the measured pitch angle distributions and using the universal distribution. When the measured pitch angle was N[-3°,4°], the average TS of S. japonicus with body length of 12.04–22.17 cm at four frequencies was -48.88 dB, -49.14 dB, -49.75 dB and -48.55 dB, respectively. The regression intercept (b20) in TS–body length equation was -73.27 dB, -73.56 dB, -74.18 dB and -73.46 dB, respectively. Variation in TS range at 0–300 m depth was about 10 dB. The simulated broadband target strength spectrum shows the scattering characteristics of individuals with different swim bladder length between 0–250 kHz. These results could be used for identification of S. japonicus in echograms and provide reference for acoustic stock assessment of S. japonicus in the Northwest Pacific Ocean.

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Section: Ts Estimationmentioning

confidence: 99%

Impacts of Morphological Characteristics on Target Strength of Chub Mackerel (Scomber japonicus) in the Northwest Pacific Ocean

et al. 2022

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“…The minimum TS can be derived from in situ measurements (e.g. Gastauer et al, 2016), ex situ distributions or theoretical models. This procedure has been implemented in commercial software (see Parker-Stetter et al, 2009, for details).…”

Section: Introductionmentioning

confidence: 99%

A probabilistic procedure for estimating an optimal echo-integration threshold using the Expectation-Maximisation algorithm

López-Serrano

Ortíz

Nevárez-Martı́nez

2018

Aquat. Living Resour.

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To obtain reliable fish biomass estimates by acoustic methods, it is essential to filter out the signals from unwanted scatterers (e.g. zooplankton). When acoustic data are collected at more than one frequency, methods that exploit the differences in reflectivity of scatterers can be used to achieve the separation of targets. These methods cannot be applied with historical data nor recent data collected on board fishing vessels employed as scientific platforms, where only one transducer is available. Instead, a volume backscattering strength (Sv) threshold is set to separate fish from plankton, both for echogram visualisation or, more importantly, during echo-integration. While empirical methods exist for selecting a threshold, it often depends on the subjective decision of the user. A−47 dB threshold was empirically established in 2008 at the beginning of a series of surveys conducted by Mexico's National Fisheries Institute to assess the biomass of Pacific sardine in the Gulf of California. Until 2012, when a 120 kHz transducer was installed, only data collected at 38 kHz are available. Here, we propose a probabilistic procedure to estimate an optimal Sv threshold using the Expectation-Maximisation algorithm for fitting a mixture of Gaussian distributions to Sv data sampled from schools associated with small pelagic fish and their surrounding echoes. The optimal threshold is given by the Bayes decision function for classifying an Sv value in one of the two groups. The procedure was implemented in the R language environment. The optimal threshold found for 38 kHz data was −59.4 dB, more than 12 dB lower than the currently used value. This difference prompts the need to revise the acoustic biomass estimates of small pelagics in the Gulf of California.

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“…Shape input information for such models require an accurate representation of a real swimbladder shape which can be obtained by the dissection of the species 28 or by means of X-ray scan 29,30 . Even more detailed images can be obtained through Computer Tomography scans (CT) and Magnetic resonance imaging (MRI) 31,32 . These techniques are now in use for the implementation of approximation models such as the deformed cylinder model (DCM), and Kirchhoff Ray Mode model (KRM) 33,34 , along with complex numerical models that solve wave equations on finite surface elements, such as the Boundary Element Method (BEM) and the Finite Element Method (FEM) 35,36 .…”

Section: Introductionmentioning

confidence: 99%

Characterization of European sprat acoustic backscatter

Palermino,

Gastauer,

Felice

et al. 2024

Preprint

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In fisheries acoustics, the identification of targets and precise translation of acoustic energy into biological meaningful metrics remains a challenge. Backscattering cross-section, or its logarithmic form, Target Strength (TS, dB re 1 m2), is a key parameter in this process. There are numerous studies on commercially important species, but few studies are available on commercially non-important species, such as the European sprat in the Mediterranean Sea. The application of backscattering models can improve our understanding of the acoustic properties of these species, allowing the manipulation of key parameters affecting the TS. Here we applied several backscattering models, on three-dimensional swimbladder shapes derived from Computer Tomography (CT) scans, of sprat collected during the MEDiterranean International Acoustic Survey (MEDIAS) in 2021. The theoretical TS pattern was compared with empirical TS revealing a good fit at 38 and 70 kHz between 0° (broadside incidence) and − 20° and significant differences at higher frequencies and tilt angles. This study provides estimates of the relative frequency response and broadband backscatter of sprat in the Mediterranean Sea. Moreover, the relationship of TS with fish length at 38 kHz yields a new relevant conversion parameter (b20) of -68.3 dB re 1 m2 for European sprat in the Mediterranean Sea.

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Target strength estimates of red emperor (Lutjanus sebae) with Bayesian parameter calibration

Cited by 9 publications

References 45 publications

Impacts of Morphological Characteristics on Target Strength of Chub Mackerel (Scomber japonicus) in the Northwest Pacific Ocean

Impacts of Morphological Characteristics on Target Strength of Chub Mackerel (Scomber japonicus) in the Northwest Pacific Ocean

A probabilistic procedure for estimating an optimal echo-integration threshold using the Expectation-Maximisation algorithm

Characterization of European sprat acoustic backscatter

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