Modelling and in situ observation of broadband acoustic scattering from the Silver cyprinid (Rastrineobola argentea) in Lake Victoria, East Africa

Yang Yang; Sven Gastauer; Roland Proud; Richard Mangeni-Sande; Inigo Everson; Robert J Kayanda; Andrew S Brierley

doi:10.1093/icesjms/fsad137

Modelling and in situ observation of broadband acoustic scattering from the Silver cyprinid (Rastrineobola argentea) in Lake Victoria, East Africa

Yang Yang^*, Sven Gastauer, Roland Proud, Richard Mangeni-Sande, Inigo Everson, Robert J Kayanda, Andrew S Brierley

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

Abstract

Lake Victoria is the second-largest freshwater lake in the world, and fish from the lake are a vital food resource for millions of people living around it. The silver cyprinid (Rastrineobola argentea), a small schooling pelagic species known in Tanzania as “dagaa” contributes ca. 55% to the total annual catch (ca. 0.51 million tonnes (MT) in 2014). The acoustic target strength (TS, dB re 1 m²) of dagaa, a key factor for biomass estimation, is however not well described, and is a major source of uncertainty in biomass estimation. In this study, we developed a Kirchhoff-ray mode (KRM) model to predict the TS of dagaa at standard fisheries survey frequencies. The model was based on the morphology of the body and the dual-chambered swimbladder, as obtained from X-ray images of fish ranging in total length (TL) between 2.8 and 5.4 cm. The results suggested that the swimbladder (which comprises 2.6 to 8.2% of body volume) accounts for ca. 65 to 90% of the total backscattering at 120 kHz. The predicted TS was highly dependent on tilt angle, varying by 14.0 dB at 120 kHz across the tilt range 65–115˚ (where 0˚ is head up and 180˚ is tail up), and TS variability with tilt generally increased with increasing frequency. The tilt angle of acoustically tracked individual fish indicated a distribution of tilt angles with a mean and s.d. of 93.5 and 15.1°. Our model suggested a new tilt-averaged TS–TL relationship for dagaa [TS120 kHz=19.49log(TL)−70.3], which leads to a TS 1.5 dB higher than the value in the relationship presently used to estimate stock biomass. The new relationship will lead to a substantial reduction (by ca. 30%) in estimated biomass. The discrepancies between the mean relative frequency response of the in situ measurements of backscatter from dagaa and the KRM model predictions were in the range of -2.9–3.1 dB at frequencies from 45 to 250 kHz. The KRM modelling and in situ broadband measurements of dagaa will be beneficial for acoustic identification and behavioural studies of dagaa, and will enable improved biomass assessment, thereby underpinning sustainable long-term management.

Original language	English
Article number	fsad137
Journal	ICES Journal of Marine Science
Volume	Advance article
Early online date	1 Sept 2023
DOIs	https://doi.org/10.1093/icesjms/fsad137
Publication status	E-pub ahead of print - 1 Sept 2023

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Yang_2023_ICESJMS_Broadbandacousticscattering_CCBY
Copyright © The Author(s) 2023. Published by Oxford University Press on behalf of International Council for the Exploration of the Sea. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
Final published version, 1.87 MBLicence: CC BY

Modelling and in situ observation of broadband acoustic scattering from the Silver cyprinid (Rastrineobola argentea) in Lake Victoria, East Africa (code)
Yang, Y. (Creator), Proud, R. H. (Creator), Mangeni, R. S. (Creator) & Brierley, A. S. (Creator), GitHub, 2023
https://github.com/yangyangMarine/KRM_dagaa
Dataset: Software

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Yang, Y., Gastauer, S., Proud, R., Mangeni-Sande, R., Everson, I., Kayanda, R. J., & Brierley, A. S. (2023). Modelling and in situ observation of broadband acoustic scattering from the Silver cyprinid (Rastrineobola argentea) in Lake Victoria, East Africa. ICES Journal of Marine Science, Advance article, Article fsad137. Advance online publication. https://doi.org/10.1093/icesjms/fsad137

@article{e11d88f58cd246f699a81322694d82cc,

title = "Modelling and in situ observation of broadband acoustic scattering from the Silver cyprinid (Rastrineobola argentea) in Lake Victoria, East Africa",

abstract = "Lake Victoria is the second-largest freshwater lake in the world, and fish from the lake are a vital food resource for millions of people living around it. The silver cyprinid (Rastrineobola argentea), a small schooling pelagic species known in Tanzania as “dagaa” contributes ca. 55% to the total annual catch (ca. 0.51 million tonnes (MT) in 2014). The acoustic target strength (TS, dB re 1 m2) of dagaa, a key factor for biomass estimation, is however not well described, and is a major source of uncertainty in biomass estimation. In this study, we developed a Kirchhoff-ray mode (KRM) model to predict the TS of dagaa at standard fisheries survey frequencies. The model was based on the morphology of the body and the dual-chambered swimbladder, as obtained from X-ray images of fish ranging in total length (TL) between 2.8 and 5.4 cm. The results suggested that the swimbladder (which comprises 2.6 to 8.2% of body volume) accounts for ca. 65 to 90% of the total backscattering at 120 kHz. The predicted TS was highly dependent on tilt angle, varying by 14.0 dB at 120 kHz across the tilt range 65–115˚ (where 0˚ is head up and 180˚ is tail up), and TS variability with tilt generally increased with increasing frequency. The tilt angle of acoustically tracked individual fish indicated a distribution of tilt angles with a mean and s.d. of 93.5 and 15.1°. Our model suggested a new tilt-averaged TS–TL relationship for dagaa [TS120 kHz=19.49log(TL)−70.3], which leads to a TS 1.5 dB higher than the value in the relationship presently used to estimate stock biomass. The new relationship will lead to a substantial reduction (by ca. 30%) in estimated biomass. The discrepancies between the mean relative frequency response of the in situ measurements of backscatter from dagaa and the KRM model predictions were in the range of -2.9–3.1 dB at frequencies from 45 to 250 kHz. The KRM modelling and in situ broadband measurements of dagaa will be beneficial for acoustic identification and behavioural studies of dagaa, and will enable improved biomass assessment, thereby underpinning sustainable long-term management.",

author = "Yang Yang and Sven Gastauer and Roland Proud and Richard Mangeni-Sande and Inigo Everson and Kayanda, {Robert J} and Brierley, {Andrew S}",

note = "Funding: YY was funded by the China Scholarship Council. This work was supported by a grant from the UK Royal Society under the “International Collaboration” theme to ASB and RJK.",

year = "2023",

month = sep,

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doi = "10.1093/icesjms/fsad137",

language = "English",

volume = "Advance article",

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publisher = "Oxford University Press",

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TY - JOUR

T1 - Modelling and in situ observation of broadband acoustic scattering from the Silver cyprinid (Rastrineobola argentea) in Lake Victoria, East Africa

AU - Yang, Yang

AU - Gastauer, Sven

AU - Proud, Roland

AU - Mangeni-Sande, Richard

AU - Everson, Inigo

AU - Kayanda, Robert J

AU - Brierley, Andrew S

N1 - Funding: YY was funded by the China Scholarship Council. This work was supported by a grant from the UK Royal Society under the “International Collaboration” theme to ASB and RJK.

PY - 2023/9/1

Y1 - 2023/9/1

N2 - Lake Victoria is the second-largest freshwater lake in the world, and fish from the lake are a vital food resource for millions of people living around it. The silver cyprinid (Rastrineobola argentea), a small schooling pelagic species known in Tanzania as “dagaa” contributes ca. 55% to the total annual catch (ca. 0.51 million tonnes (MT) in 2014). The acoustic target strength (TS, dB re 1 m2) of dagaa, a key factor for biomass estimation, is however not well described, and is a major source of uncertainty in biomass estimation. In this study, we developed a Kirchhoff-ray mode (KRM) model to predict the TS of dagaa at standard fisheries survey frequencies. The model was based on the morphology of the body and the dual-chambered swimbladder, as obtained from X-ray images of fish ranging in total length (TL) between 2.8 and 5.4 cm. The results suggested that the swimbladder (which comprises 2.6 to 8.2% of body volume) accounts for ca. 65 to 90% of the total backscattering at 120 kHz. The predicted TS was highly dependent on tilt angle, varying by 14.0 dB at 120 kHz across the tilt range 65–115˚ (where 0˚ is head up and 180˚ is tail up), and TS variability with tilt generally increased with increasing frequency. The tilt angle of acoustically tracked individual fish indicated a distribution of tilt angles with a mean and s.d. of 93.5 and 15.1°. Our model suggested a new tilt-averaged TS–TL relationship for dagaa [TS120 kHz=19.49log(TL)−70.3], which leads to a TS 1.5 dB higher than the value in the relationship presently used to estimate stock biomass. The new relationship will lead to a substantial reduction (by ca. 30%) in estimated biomass. The discrepancies between the mean relative frequency response of the in situ measurements of backscatter from dagaa and the KRM model predictions were in the range of -2.9–3.1 dB at frequencies from 45 to 250 kHz. The KRM modelling and in situ broadband measurements of dagaa will be beneficial for acoustic identification and behavioural studies of dagaa, and will enable improved biomass assessment, thereby underpinning sustainable long-term management.

AB - Lake Victoria is the second-largest freshwater lake in the world, and fish from the lake are a vital food resource for millions of people living around it. The silver cyprinid (Rastrineobola argentea), a small schooling pelagic species known in Tanzania as “dagaa” contributes ca. 55% to the total annual catch (ca. 0.51 million tonnes (MT) in 2014). The acoustic target strength (TS, dB re 1 m2) of dagaa, a key factor for biomass estimation, is however not well described, and is a major source of uncertainty in biomass estimation. In this study, we developed a Kirchhoff-ray mode (KRM) model to predict the TS of dagaa at standard fisheries survey frequencies. The model was based on the morphology of the body and the dual-chambered swimbladder, as obtained from X-ray images of fish ranging in total length (TL) between 2.8 and 5.4 cm. The results suggested that the swimbladder (which comprises 2.6 to 8.2% of body volume) accounts for ca. 65 to 90% of the total backscattering at 120 kHz. The predicted TS was highly dependent on tilt angle, varying by 14.0 dB at 120 kHz across the tilt range 65–115˚ (where 0˚ is head up and 180˚ is tail up), and TS variability with tilt generally increased with increasing frequency. The tilt angle of acoustically tracked individual fish indicated a distribution of tilt angles with a mean and s.d. of 93.5 and 15.1°. Our model suggested a new tilt-averaged TS–TL relationship for dagaa [TS120 kHz=19.49log(TL)−70.3], which leads to a TS 1.5 dB higher than the value in the relationship presently used to estimate stock biomass. The new relationship will lead to a substantial reduction (by ca. 30%) in estimated biomass. The discrepancies between the mean relative frequency response of the in situ measurements of backscatter from dagaa and the KRM model predictions were in the range of -2.9–3.1 dB at frequencies from 45 to 250 kHz. The KRM modelling and in situ broadband measurements of dagaa will be beneficial for acoustic identification and behavioural studies of dagaa, and will enable improved biomass assessment, thereby underpinning sustainable long-term management.

U2 - 10.1093/icesjms/fsad137

DO - 10.1093/icesjms/fsad137

M3 - Article

SN - 1054-3139

VL - Advance article

JO - ICES Journal of Marine Science

JF - ICES Journal of Marine Science

M1 - fsad137

ER -

Modelling and in situ observation of broadband acoustic scattering from the Silver cyprinid (Rastrineobola argentea) in Lake Victoria, East Africa

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Modelling and in situ observation of broadband acoustic scattering from the Silver cyprinid (Rastrineobola argentea) in Lake Victoria, East Africa (code)

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