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

Ultrasonic monitoring of early larval development of fish in tanks. Case study: Gilthead seabream (Sparus aurata)

Preliminary target strength measurement of Sprattus sprattus and its influence on biomass estimates in the Adriatic Sea (Mediterranean Sea)

Effect of hauling and soaking time of stationary lift nets on fish aggregation using a hydroacoustic monitoring approach

This study was funded by AZTI-Tecnalia and supported by the
research projects JAULA for the ex situ measurements and
JUVENA for the in situ ones. The project JAULA was funded by
the Department of Agriculture, Fisheries and Food of the Basque
Country Government; we thank Unai Cotano, the leader of the
project, for giving us access to the cage and for providing biological sampling information. We would like to thank the crew from
the Itsas Lagunak for providing us with the anchovy specimens,
the Aquaculture School from Mutriku for keeping the specimens
during the acclimatization period and the technician and diver
Gaizka Bidegain from AZTI for the maintenance and underwater
inspection of the specimens used throughout the ex situ measurements. Yolanda Lacalle is thanked for the illustration in Figure 2.
The project JUVENA was co-funded by the Direccio? n de
Innovacio? n y Desarrollo Tecnolo? gico, Viceconsejer??a de Pol??tica e
Industria Alimentaria, Dpto. Agricultura, Pesca y Alimentacio? n
of the Basque Government and the Secretar??a General del Mar,
Ministerio de Agricultura, Alimentacio? n y Medio Ambiente of
the Spanish Government. Thanks also to Andre?s Uriarte (Azti)
for improving this work with his valuable comments and to
Mathieu Doray and Laurent Berger (Ifremer) for their helpful
suggestions regarding the analysis and the interpretation of the
results. Finally, thanks to the anonymous contribution of the
reviewers for helping improve the quality and readability of this
work.

Ex situ and in situ target strength measurements of European anchovy in the Bay of Biscay

espanolEl uso de tecnicas acusticas para la medida y caracterizacion de biomasa de especies submarinas, constituye la mas importante herramienta en el control y explotacion de los recursos pesqueros. En la actualidad, la acuicultura supone una alternativa real a la sobreexplotacion de los ecosistemas marinos, y el desarrollo de herramientas tecnologicas para el control y mejora de la gestion de las granjas marinas es una fuerte demanda del sector. La determinacion de la biomasa total en una jaula flotante por medios acusticos sigue siendo un problema abierto, y el primer paso necesario es la caracterizacion acustica de las especies de mas interes economico, como es el caso de la dorada, �Sparus Aurata�. Presentamos el dispositivo experimental para la medida de la fuerza del blanco o target strength de la dorada en jaulas flotantes, tanto dorsal como ventralmente, y los primeros resultados experimentales. EnglishThe use of acoustical techniques to measure and to characterize the underwater species biomass is the most important tool in the control and exploitation of fisheries. Nowadays, aquaculture represents a real alternative to the overexploitation of marine ecosystems, and the development of technological tools to control and to improve the marine farm management becomes a strong sectoral demand. The acoustical determination of the total biomass in a floating cage is still an open problem, and the first step is the acoustical characterization of the species of more economical interest, like the gilt-head sea bream, �Sparus Aurata�. We present the experimental setup for the target strength measurement, dorsally and ventrally, and the first results.

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Medida in situ de la sección eficaz de dispersión de la dorada (Sparus Aurata)

We have studied the application of ultrasonic techniques in marine aquaculture: in particular,monitoring of present biomass in open sea farming cages. The final goals are school behaviour controland the estimation of number and growing rate of the fishes. In order to fulfil these objectives it isnecessary to measure the dorsal and ventral cross-section of the species of interest, in differentmonostatic and bistatic configurations, using low cost commercial transducers that could be placed inproduction conditions.

/pdf/gilt-head-sea-bream-sparus-aurata-cross-section-measurements-5in4oi98la.pdf

Gilt-head sea-bream (Sparus aurata) cross-section measurements for the acoustical control of sea farms

We report on a new type of localized structure, an ultrasonic cavity soliton, supported by large aspect-ratio acoustic resonators containing viscous media. These states of the acoustic and thermal fields are robust structures, existing whenever a spatially uniform solution and a periodic pattern coexist. We derive the equations which describe the system including spatial effects. The spatio-temporal dynamics of the system is analyzed from the microscopic model, and the results are in good agreement with the numerical results, such as with previous experimental works.

Localized structures and pattern formation in acoustic resonator containing viscous fluid

The aim of this work is to obtain reference values for the acoustic properties (c,) of skipjack
tuna spine and flesh. These parameters rule the backscattering of acoustic energy when an
ultrasonic beam insonifies the target, and the target strength of the fish target is dependent on
them. Therefore, to characterize the acoustic response (target strength, TS) of a target is
necessary to know the value of c and . The acoustic parameters depend on the fish species –
and, for the same species, depend on the fat content, the age…- and also depend on the working ultrasonic frequency.

Víctor Espinosa Roselló

Papers

Ex situ and in situ target strength measurements of European anchovy in the Bay of Biscay

Medida in situ de la sección eficaz de dispersión de la dorada (Sparus Aurata)

Gilt-head sea-bream (Sparus aurata) cross-section measurements for the acoustical control of sea farms

Localized structures and pattern formation in acoustic resonator containing viscous fluid

Measurement of acoustic impedance of skipjack tuna (Katsuwonus pelamis) tissues