Extraction and comparison of acoustic backscatter from a calibrated multi- and single-beam sonar

Abstract Multi-beam sonar is potentially a powerful analytical tool for investigating the acoustic properties and behaviour of fish in relation to quantitative fisheries research. The SIMRAD SM2000 is a 200 kHz multi-beam sonar employing an 80-element array to transmit and synthesize, electronically, 128 receive beams (20°×2.2°) over a 180° arc simultaneously. Once calibrated, such systems enable the extraction of acoustic target strength and volume backscattering from an extended 3D ocean volume. We present an overview of the theoretical framework for the calibration of a multi-beam sonar, and then compare the acoustic backscatter from a calibrated single-beam 50 kHz echosounder with selected beams from a sphere-calibrated multi-beam sonar. Both systems recorded acoustic data from Atlantic herring contained within a weir, as the fish passed beneath the transducers. Specifically, we examine the relationship between the area-backscattering strength (Sa) from the single-beam system with the nadir beam (beam 63) of the SM2000 sonar. In addition, data are presented on the observed variability in Sa with target aspect for off-vertical angles from 15° to 60° in 15° intervals. Non-standard synthesized SM2000 beam widths are explored for both calibration and field datasets. The implications for biomass estimation are also discussed.

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In situ target strength estimates of optically verified southern blue whiting (Micromesistius australis)

ICES Journal of Marine Science ◽

10.1093/icesjms/fss177 ◽

2012 ◽

Vol 70 (2) ◽

pp. 431-439 ◽

Cited By ~ 4

Author(s):

Richard L. O'Driscoll ◽

Johannes Oeffner ◽

Adam J. Dunford

Keyword(s):

New Zealand ◽

Confidence Interval ◽

Fork Length ◽

Target Strength ◽

Blue Whiting ◽

Acoustic Target ◽

The Mean ◽

The Relationship ◽

Immature Fish

Abstract O'Driscoll, R. L., Oeffner, J., and Dunford, A. J. 2013. In situ target strength estimates of optically verified southern blue whiting (Micromesistius australis) – ICES Journal of Marine Science, 70: 431–439. Estimates of the acoustic target strength (TS) of southern blue whiting (Micromesistius australis) at 38 kHz were obtained using an autonomous acoustic–optical system (AOS) mounted on a demersal trawl. Data were collected from aggregations of spawning adult [mean fork length (FL) 34.4 cm] and immature (mean FL 24.6 cm) southern blue whiting south of New Zealand. Mean TS was estimated from 162 tracks containing 695 echoes from targets identified from video as southern blue whiting. The mean TS was –37.9 dB with a 95% confidence interval (CI) of –39.7 to –36.6 dB for 21 immature fish and –34.6 dB (95% CI –35.4 to –34.0 dB) for 141 adults. A logarithmic fit through the mean TS values produced a TS–fork length (FL) relationship from optically verified targets of TS = 22.06 log10FL – 68.54. This new relationship gives TS values within 1 dB of those estimated using the relationship recently adopted by ICES for blue whiting (Micromesistius poutassou) of TS = 20 log10TL – 65.2 (where TL is total length) obtained from in situ measurements, but higher values than those estimated from the previous relationship for southern blue whiting of TS = 38 log10FL – 97, which was based on swimbladder modelling.

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Corrigendum to: In situ target strength measurement of the black triggerfish Melichthys niger and the ocean triggerfish Canthidermis sufflamen

Marine and Freshwater Research ◽

10.1071/mf19153_co ◽

2021 ◽

Vol 72 (3) ◽

pp. 449

Author(s):

Julie Salvetat ◽

Anne Lebourges-Dhaussy ◽

Paulo Travassos ◽

Sven Gastauer ◽

Gildas Roudaut ◽

...

Keyword(s):

Target Strength ◽

Biomass Estimation ◽

Tropical Islands ◽

Acoustic Data ◽

North East ◽

Fernando De Noronha ◽

The Mean ◽

Tuna Fisheries ◽

Fish Aggregating Devices

Triggerfish are widely distributed in tropical waters where they play an important ecological role. The black triggerfish Melichthys niger may be the dominant species around oceanic tropical islands, whereas pelagic triggerfish, such as the ocean triggerfish Canthidermis sufflamen, can assemble around fish aggregating devices (FADs) where they are a common bycatch of tuna fisheries. In this study we combined acoustic and optical recordings to provide the first in situ target strength (TS) measurement of black and ocean triggerfish. Data were collected in the Archipelago of Fernando de Noronha off north-east Brazil. The mean TS of a 27.8-cm-long black triggerfish at 70 and 200kHz was –39.3dB re 1m2 (CV=14.0%) and –38.9dB re 1m2 (CV=14.4%) respectively. The mean TS values of ocean triggerfish (with a size range of 39–44cm) at 70 and 200kHz were –36.0dB re 1m2 (CV=15.7%) and –33.3dB re 1m2 (CV=14.0%) respectively. This work opens up the field for acoustic biomass estimates. In addition, we have shown that TS values for ocean triggerfish are within the same range as those of small tunas. Therefore, acoustic data transmitted from FADs equipped with echosounders can introduce a bias in tuna acoustic biomass estimation and lead to increased rates of bycatch.

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Kernel methods for the detection and classification of fish schools in single-beam and multibeam acoustic data

ICES Journal of Marine Science ◽

10.1093/icesjms/fsp004 ◽

2009 ◽

Vol 66 (6) ◽

pp. 1130-1135 ◽

Cited By ~ 9

Author(s):

Bart Buelens ◽

Tim Pauly ◽

Raymond Williams ◽

Arthur Sale

Keyword(s):

Kernel Methods ◽

Kernel Method ◽

Age Groups ◽

Routine Data ◽

Acoustic Properties ◽

Multibeam Sonar ◽

Single Beam ◽

Fish Schools ◽

Acoustic Data

Abstract Buelens, B., Pauly, T., Williams, R., and Sale, A. 2009. Kernel methods for the detection and classification of fish schools in single-beam and multibeam acoustic data. – ICES Journal of Marine Science, 66: 1130–1135. A kernel method for clustering acoustic data from single-beam echosounder and multibeam sonar is presented. The algorithm is used to detect fish schools and to classify acoustic data into clusters of similar acoustic properties. In a preprocessing routine, data from single-beam echosounder and multibeam sonar are transformed into an abstracted representation by multidimensional nodes, which are datapoints with spatial, temporal, and acoustic features as components. Kernel methods combine these components to determine clusters based on joint spatial, temporal, and acoustic similarities. These clusters yield a classification of the data in groups of similar nodes. Including the spatial components results in clusters for each school and effectively detects fish schools. Ignoring the spatial components yields a classification according to acoustic similarities, corresponding to classes of different species or age groups. The method is described and two case studies are presented.

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

Applied Sciences ◽

10.3390/app8091536 ◽

2018 ◽

Vol 8 (9) ◽

pp. 1536 ◽

Cited By ~ 4

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.

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Tests of Acoustic Target Strength and Bubble Dissolution Models Using a Synthetic Bubble Generator

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-19-0133.1 ◽

2020 ◽

Vol 37 (1) ◽

pp. 129-140

Author(s):

Kevin M. Rychert ◽

Thomas C. Weber

Keyword(s):

Mass Transfer Rate ◽

Gas Diffusion ◽

Test Methods ◽

Target Strength ◽

Acoustic Backscatter ◽

Acoustic Target ◽

Liquid Boundary ◽

Different Depths ◽

Bubble Sizes ◽

Good Agreement

AbstractTo test methods used for converting observations of acoustic backscatter to estimates of the volume and transport of free gas escaping the seabed, a bubble generator has been constructed and used at sea. The bubble generator creates individual bubbles of the sizes commonly associated with methane seeps, 1–5-mm radii, which can be released at preplanned rates. The bubble generator was deployed off the coast of New Hampshire at a depth of 55 m, and acoustic backscatter between 16 and 24 kHz was collected from a shipboard echo sounder while transiting over the rising bubbles. Bubble sizes and compositions (either Ar or N2) were known at the source. A model for bubble evolution, accounting for changes in bubble size and composition due to hydrostatic pressure and gas diffusion across the gas–liquid boundary, was coupled with an acoustic target strength (TS) model to generate predictions of the acoustic backscatter from bubbles that had risen to different depths. These predictions were then compared with experimental observation. Good agreement between prediction and observation was found in most cases, with the exception of the largest (4 mm) gas bubbles at depths of 30 m or less. The exact cause of this bias is unknown, but may be due to incorrect assumptions in models for the bubble TS, rise velocity, or mass transfer rate.

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Delineating the habitat of demersal fish assemblages with acoustic seabed technologies

ICES Journal of Marine Science ◽

10.1093/icesjms/fsr124 ◽

2011 ◽

Vol 68 (9) ◽

pp. 1973-1985 ◽

Cited By ~ 9

Author(s):

Jeroen van der Kooij ◽

Sven Kupschus ◽

Beth E. Scott

Keyword(s):

Species Composition ◽

Fish Assemblages ◽

Demersal Fish ◽

Single Beam ◽

Explanatory Variables ◽

Acoustic Data ◽

Spatial Management ◽

Fish Habitats ◽

The Relationship ◽

Demersal Species

Abstract van der Kooij, J., Kupschus, S., and Scott, B. E. 2011. Delineating the habitat of demersal fish assemblages with acoustic seabed technologies. – ICES Journal of Marine Science, 68: 1973–1985. Habitats influence species distribution and, although the seabed is an important habitat factor for demersal species, traditional sampling methods often provide no practical solution to investigating the seabed over large areas. The ability of a multivariate method that utilizes single-beam acoustic seabed data combined with species composition data to define demersal fish habitats was tested. The best model explained 19.4% of the variance observed in the species data and was robust between years. Ten biotopes were identified, each containing species that, either alone or in combination with others, were indicative of that biotope. Using unclassified acoustic seabed data as explanatory variables, discrepancies between the numbers of acoustically distinct classes and species assemblages, as previously reported in the literature, were avoided, while utilizing their relationship with community structure. The study focused on the relationship between simultaneously recorded species composition and seabed data from fishing stations, but because continuous acoustic data along the survey tracks were available between stations, the model could be used to predict the spatial extent of the biotopes. Although the method was developed with the eventual aim of providing a meaningful foundation to the spatial management of mixed fisheries, it could also contribute to applications in spatial planning.

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In situ target strength measurement of the black triggerfish Melichthys niger and the ocean triggerfish Canthidermis sufflamen

Marine and Freshwater Research ◽

10.1071/mf19153 ◽

2020 ◽

Vol 71 (9) ◽

pp. 1118

Author(s):

Julie Salvetat ◽

Anne Lebourges-Dhaussy ◽

Paulo Travassos ◽

Sven Gastauer ◽

Gildas Roudaut ◽

...

Keyword(s):

Target Strength ◽

Biomass Estimation ◽

Tropical Islands ◽

Acoustic Data ◽

North East ◽

Fernando De Noronha ◽

The Mean ◽

Tuna Fisheries ◽

Fish Aggregating Devices

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A revised target strength–length estimate for blue whiting (Micromesistius poutassou): implications for biomass estimates

ICES Journal of Marine Science ◽

10.1093/icesjms/fsr142 ◽

2011 ◽

Vol 68 (10) ◽

pp. 2222-2228 ◽

Cited By ~ 6

Author(s):

Geir Pedersen ◽

Olav Rune Godø ◽

Egil Ona ◽

Gavin J. Macaulay

Keyword(s):

Target Strength ◽

Similar Species ◽

The West ◽

Norwegian Sea ◽

Blue Whiting ◽

Length Relationship ◽

Abundance Estimates ◽

Acoustic Target ◽

Length Estimate ◽

The Relationship

Abstract Pedersen, G., Godø, O. R., Ona, E., and Macaulay, G. J. 2011. A revised target strength–length estimate for blue whiting (Micromesistius poutassou): implications for biomass estimates. – ICES Journal of Marine Science, 68: 2222–2228. Acoustic abundance estimates of blue whiting have generally been higher than estimates based on catch data. One explanation has been that the relationship between acoustic target strength (TS) and length is too low and hence overestimates the number of fish. Measurements of TS were conducted during surveys of blue whiting in March/April 2003–2007 to the west of the British Isles from several different measurement platforms, and also during August 2005 in the Norwegian Sea. Results from these experiments confirm the view that the existing TS–length relationship is too low. A new TS–length relationship is proposed that is ∼5 dB higher. Blue whiting TS is considerably higher than observed and modelled for a similar species, southern blue whiting (Micromesistius australis).

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Quantitative Measurements of Euphausiids Using a 120-kHz Sounder and Their in situ Orientation

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f80-087 ◽

1980 ◽

Vol 37 (4) ◽

pp. 693-702 ◽

Cited By ~ 38

Author(s):

D. D. Sameoto

Keyword(s):

Acoustic Scattering ◽

Biological Data ◽

Target Strength ◽

Acoustic Data ◽

Quantitative Measurements ◽

Underwater Photography ◽

Average Orientation ◽

Opening And Closing ◽

The Relationship

Biomass and density of euphausiids were estimated using a 120-kHz sounder during 2 y in the Gulf of St. Lawrence. Simultaneously, biological samples were taken with two types of multiple opening and closing nets: MOCNESS-type and BIONESS. Correlations for biomass and density estimates between the acoustic and biological data range from 0.391 to 0.791. Acoustic data showed that a high percentage of euphausiids avoided the MOCNESS-type net during the day. A comparison of the relationship between biological and acoustic data for both years showed that the BIONESS sampler captured euphausiids more efficiently during both day and night. Target strength of the euphausiids estimated from acoustic and biological data showed that it was lower than would be expected if the animals were oriented horizontally. Photographs taken from the BIONESS sampler at depths having acoustic scattering layers showed that the average orientation of euphausiids changed with time, the average orientation being closest to horizontal during daytime. Orientation changed from 27° from the horizontal at 14:00 to 51° during 02:00. The effect of orientation on target strength is discussed.Key words: euphausiids, acoustics, orientation, biomass, underwater photography, multiple net samplers, zooplankton

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