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

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

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.

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

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.

scholarly journals In situ target-strength measurements of Chilean jack mackerel (Trachurus symmetricus murphyi) collected with a scientific echosounder installed on a fishing vessel

2008 ◽  
Vol 65 (4) ◽  
pp. 594-604 ◽  
Author(s):  
Hector Peña
Keyword(s):  
Target Strength ◽  
Commercial Fishing ◽  
Jack Mackerel ◽  
Fishing Vessel ◽  
Acoustic Backscattering ◽  
Acoustic Data ◽  
Fishing Vessels ◽  
Single Target ◽  
The Mean

Abstract Peña, H. 2008. In situ target-strength measurements of Chilean jack mackerel (Trachurus symmetricus murphyi) collected with a scientific echosounder installed on a fishing vessel. – ICES Journal of Marine Science 65: 594–604. The use of commercial fishing vessels for scientific purposes has increased worldwide in the past 10 years. Many such studies have involved the collection of acoustic data from both uncalibrated and calibrated echosounders. However, few studies have involved investigations of in situ target strength (TS). During August/September 2003, in situ TS data on Chilean jack mackerel (Trachurus symmetricus murphyi) were collected on board a commercial purse-seiner during normal fishing operations off Chile, using a 38 kHz, Simrad EK60 scientific echosounder. The single-target detections of Chilean jack mackerel were filtered by depth, off-axis beam angle, and beam-compensation criteria to improve the quality of the data used for the TS calculations. Two methods, using raw data and tracked data, were employed to calculate the mean acoustic-backscattering cross section (σbs) and mean TS of Chilean jack mackerel. The results of the two approaches gave similar results, with a strong mode in the mean TS distribution between −35 and −37 dB for fish lengths ranging from 26 to 34 cm, indicating a b20 value of −66 dB. These results agreed well with most results published for this species and others of the same genus (i.e. T. trachurus, Trachurus t. capensis, and T. japonicus).

scholarly journals In situ target strength of bigeye tuna (Thunnus obesus) associated with fish aggregating devices

2019 ◽  
Author(s):  
G Boyra ◽  
G Moreno ◽  
B Orue ◽  
B Sobradillo ◽  
I Sancristobal
Keyword(s):  
Frequency Response ◽  
Target Strength ◽  
Species Discrimination ◽  
Bigeye Tuna ◽  
Central Pacific ◽  
Commercial Fish ◽  
Thunnus Obesus ◽  
Tropical Tuna ◽  
Fish Aggregating Devices

Abstract Bigeye tuna (Thunnus obesus) is an important commercial fish species, which aggregates around fish aggregating devices (FADs) together with other tropical tuna species. Acoustics is the main technology used by fishers and scientists for the location and quantification of tunas at FADs. However, currently it is not possible to reliably discriminate between the different tropical tuna species that are found together at FADs using acoustic methods, which hampers the development of selective fishing needed to preserve some of the tropical tuna species for which overfishing is occurring. One of the prerequisites for species discrimination is to know the target strength (TS) of each species at different frequencies. This paper measures in situ TS values and explores the frequency response of bigeye tuna at FADs in the central Pacific Ocean using three different acoustic frequencies. For the range of body length caught (40–100 cm), the obtained b20 values were −65, −66, and −72 dB for 38, 120, and 200 kHz, respectively. The decreasing frequency response pattern obtained for this swimbladder bearing species contrasts with the opposite pattern previously observed for skipjack tuna (bladder-less), the most abundant tuna species found at FADs, hence allowing the potential for discrimination between the two species.

scholarly journals In situ target-strength measurement of young hairtail (Trichiurus haumela) in the Yellow Sea

2006 ◽  
Vol 63 (1) ◽  
pp. 46-51 ◽  
Author(s):  
Xianyong Zhao
Keyword(s):  
Confidence Interval ◽  
Yellow Sea ◽  
The Yellow Sea ◽  
Target Strength ◽  
Abundance Estimation ◽  
Strength Measurement ◽  
The Mean

Abstract The target strength of hairtail (Trichiurus haumela) in the Yellow Sea was measured in situ with a 38 kHz, split-beam echosounder on 2 January 2001. The fish measured were of the 2000 year class, its anal length ranged from 62 to 115 mm, with a mean of 89.8 mm. The mean target strength of these young hairtail was estimated to be −49.2 dB, with a 95% confidence interval of (−49.4, −49.0) dB. This provided a rare and useful reference for the acoustic-abundance estimation of hairtail.

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

2012 ◽  
Vol 70 (2) ◽  
pp. 431-439 ◽  
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.

scholarly journals Measuring herring densities with one real and several phantom research vessels

2009 ◽  
Vol 66 (6) ◽  
pp. 1264-1269 ◽  
Author(s):  
Ruben Patel ◽  
Egil Ona
Keyword(s):  
Pelagic Fish ◽  
Target Strength ◽  
Fish Biomass ◽  
Marine Science ◽  
Lateral Aspect ◽  
Multibeam Sonar ◽  
The Real ◽  
Backscattering Strength ◽  
The Mean

Abstract Patel, R., and Ona, E. 2009. Measuring herring densities with one real and several phantom research vessels. – ICES Journal of Marine Science 66: 1264–1269. Vessel-induced avoidance can potentially cause a large bias in acoustic estimates of schooling, pelagic-fish biomass. This paper presents a method for quantifying this uncertainty. Volume-backscattering strength (Sv) from a horizontally projecting, multibeam sonar (Simrad MS70) is resampled to form synthetic, vertical, echosounder beams to the side of the survey vessel. These data are analysed as if they were collected from phantom vessels surveying parallel transects at fixed ranges from the real vessel. The nautical-area-backscattering coefficients (sA) from the synthetic echograms are compared with those measured by conventional 70 and 120 kHz echosounders (Simrad EK60) on the real vessel. Data collected in 2006 from schools of Norwegian spring-spawning herring are used to illustrate the method and explore its limitations. Potential effects of vessel-induced avoidance are evaluated by comparing the mean sA values observed from the phantom vessels with those observed from the real vessel. The technique also allows direct estimates of the mean lateral-aspect target strength of in situ herring.

scholarly journals A statistical approach to quantify uncertainty in carbon monoxide measurements at the Izaña global GAW station: 2008–2011

2012 ◽  
Vol 5 (5) ◽  
pp. 6949-6989 ◽  
Author(s):  
A. J. Gomez-Pelaez ◽  
R. Ramos ◽  
V. Gomez-Trueba ◽  
P. C. Novelli ◽  
R. Campo-Hernandez
Keyword(s):  
Carbon Monoxide ◽  
Response Function ◽  
Measurement System ◽  
Minimum Variance ◽  
Standard Uncertainty ◽  
In Situ Measurements ◽  
North East ◽  
The Mean ◽  
Mean Differences

Abstract. Atmospheric CO in-situ measurements are carried out at the Izaña (Tenerife) global GAW mountain station using a RGA (Reduction Gas Analyser). In-situ measurements at Izaña are representative of the subtropical North-East Atlantic free troposphere, specially during the night period. We present the measurement system configuration, the response function, the calibration scheme, the data processing, the Izaña's 2008–2011 CO nocturnal time series, and the mean diurnal cycle by months. We have developed a rigorous uncertainty analysis for carbon monoxide measurements carried out at the Izaña station which could be applied to other GAW stations. We determine the combined standard uncertainty from four components of the measurement: uncertainty of the WMO standard gases interpolated over the range of measurement, the uncertainty that takes into account the agreement between the standard gases and the response function used, the uncertainty due to the repeatability of the injections, and the propagated uncertainty related to the response function parameters uncertainties (which also takes into account the covariance between the parameters). The mean value of the combined standard uncertainty decreased significantly after March 2009, from 2.37 nmol mol−1 to 1.66 nmol mol−1, due to improvements in the measurement system. A fifth type of uncertainty we call representation uncertainty is considered when some of the data necessary to compute exactly the mean are absent. Any computed mean has also a propagated uncertainty arising from the uncertainties of the data used to compute the mean. The law of propagation depends on the type of uncertainty component (random or systematic). In-situ hourly means are compared with simultaneous and collocated NOAA flask samples. The uncertainty in the differences is determined and whether these are significant. For 2009–2011, only 24.5% of the differences are significant, and 68% of the differences are between −2.39 and 2.5 nmol mol−1. Total and annual mean differences are computed using conventional expressions but also expressions with weights based on the minimum variance method. The annual mean differences for 2009–2011 are well within the ±2 nmol mol−1 compatibility goal of GAW.

Effects of variable mean target strength on estimates of abundance: the case of Atlantic mackerel (Scomber scombrus)

2016 ◽  
Vol 74 (3) ◽  
pp. 822-831 ◽  
Author(s):  
Ben Scoulding ◽  
Sven Gastauer ◽  
David N. MacLennan ◽  
Sascha M. M. Fässler ◽  
Phillip Copland ◽  
...  
Keyword(s):  
Stock Assessment ◽  
Target Strength ◽  
Fish School ◽  
Acoustic Data ◽  
Atlantic Mackerel ◽  
Scomber Scombrus ◽  
North East ◽  
The North ◽  
Frequency Split ◽  
Abundance And Distribution

Atlantic mackerel Scomber scombrus is a small pelagic, migratory fish which supports commercial fisheries. These fish school and are detectable using echosounders, yet fishery-independent estimates of their abundance in the North East Atlantic do not consider acoustic data. Accurate estimates of mean target strength (TS) are presently limiting echo-integration surveys from providing useful estimates of Atlantic mackerel abundance and distribution. This study provides TS estimates for in situ mackerel from multi-frequency split-beam echosounder measurements. TS equals −52.79 dB at 18 kHz, −59.60 dB at 38 kHz, −55.63 dB at 120 kHz, and −53.58 dB at 200 kHz, for a mean mackerel total length = 33.3 cm. These values differ from those currently assumed for this species in analyses of acoustic survey data. We investigate the sensitivity of acoustically estimated mackerel biomass around the Shetland Islands, Scotland, in 2014, to various estimates of TS. Confidence limits were obtained using geostatistics accounting for coverage and spatial autocorrelation. Stock biomasses, estimated from 38 and 200 kHz data, differed by 10.5%, and stock distributions were similar to each other and to the estimates from an independent stock assessment. Because mackerel backscatter at 38 kHz is dominated by echoes from the flesh and may have similarities to echoes from fish with swimbladders, and backscatter at 200 kHz is dominated by relatively stable echoes from the backbone, we recommend using 200 kHz data for estimates of Atlantic mackerel biomass.

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

2003 ◽  
Vol 60 (3) ◽  
pp. 669-677 ◽  
Author(s):  
Gary D Melvin ◽  
Norman A Cochrane ◽  
Yanchao Li
Keyword(s):  
Acoustic Properties ◽  
Target Strength ◽  
Acoustic Backscatter ◽  
Biomass Estimation ◽  
Single Beam ◽  
Acoustic Data ◽  
Powerful Analytical Tool ◽  
Acoustic Target ◽  
Element Array ◽  
The Relationship

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.

scholarly journals A Bayesian approach to estimating target strength

2009 ◽  
Vol 66 (6) ◽  
pp. 1197-1204 ◽  
Author(s):  
Sascha M. M. Fässler ◽  
Andrew S. Brierley ◽  
Paul G. Fernandes
Keyword(s):  
Bayesian Approach ◽  
Tilt Angle ◽  
Clupea Harengus ◽  
Target Strength ◽  
Model Parameters ◽  
Fish Length ◽  
Acoustic Data ◽  
Abundance Estimates ◽  
The Mean ◽  
Conventional Models

Abstract Fässler, S. M. M., Brierley, A. S., and Fernandes, P. G. 2009. A Bayesian approach to estimating target strength. – ICES Journal of Marine Science, 66: 1197–1204. Currently, conventional models of target strength (TS) vs. fish length, based on empirical measurements, are used to estimate fish density from integrated acoustic data. These models estimate a mean TS, averaged over variables that modulate fish TS (tilt angle, physiology, and morphology); they do not include information about the uncertainty of the mean TS, which could be propagated through to estimates of fish abundance. We use Bayesian methods, together with theoretical TS models and in situ TS data, to determine the uncertainty in TS estimates of Atlantic herring (Clupea harengus). Priors for model parameters (surface swimbladder volume, tilt angle, and s.d. of the mean TS) were used to estimate posterior parameter distributions and subsequently build a probabilistic TS model. The sensitivity of herring abundance estimates to variation in the Bayesian TS model was also evaluated. The abundance of North Sea herring from the area covered by the Scottish acoustic survey component was estimated using both the conventional TS–length formula (5.34×109 fish) and the Bayesian TS model (mean = 3.17×109 fish): this difference was probably because of the particular scattering model employed and the data used in the Bayesian model. The study demonstrates the relative importance of potential bias and precision of TS estimation and how the latter can be so much less important than the former.

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