scholarly journals Lateral-aspect, target-strength measurements of in situ herring (Clupea harengus)

2009 ◽  
Vol 66 (6) ◽  
pp. 1191-1196 ◽  
Author(s):  
Geir Pedersen ◽  
Nils Olav Handegard ◽  
Egil Ona
Keyword(s):  
Target Tracking ◽  
Clupea Harengus ◽  
Target Strength ◽  
Marine Science ◽  
Lateral Aspect ◽  
Multibeam Sonar ◽  
Dorsal Aspect ◽  
The Mean ◽  
New Challenges

Abstract Pedersen, G., Handegard, N. O., and Ona, E. 2009. Lateral-aspect, target-strength measurements of in situ herring (Clupea harengus). – ICES Journal of Marine Science, 66: 1191–1196. Surveys of schooling herring with the new multibeam sonar (Simrad MS70) pose new challenges when converting the echo energy to estimates of biomass. Because the sonar projects horizontally, data and models of lateral-aspect, herring target strength (TS) are needed. In this study, the TS of herring is measured with a horizontally projecting, split-beam echosounder (Simrad EK60). Target-tracking methods are used to estimate swimming angles relative to the horizontal (θ) of individual herring within schools and layers and to evaluate how θ and TS change with depth (z). Measurements of θ and TS are used as inputs for a model describing TS as a function of θ and z. The results indicate that the mean lateral-aspect TS of in situ herring depends on z. Moreover, the mean lateral-aspect TS is more sensitive to z than the mean dorsal-aspect TS predicted by a published model. At z = 50 m, the mean lateral-aspect TS is nearly 2.5 dB higher than the mean dorsal-aspect TS. Conversely, at z = 350 m, the lateral-aspect TS is 5 dB lower. These results suggest that herring swimbladders do not compress uniformly with increasing pressure, but compress dorsoventrally more than laterally.

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 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 Observations of in situ Atlantic bluefin tuna (Thunnus thynnus) with 500-kHz multibeam sonar

2016 ◽  
Vol 73 (8) ◽  
pp. 1975-1986 ◽  
Author(s):  
Gary D. Melvin
Keyword(s):  
Shallow Water ◽  
Prince Edward Island ◽  
Field Studies ◽  
Bluefin Tuna ◽  
Target Strength ◽  
Sea State ◽  
Multibeam Sonar ◽  
Air Bubble ◽  
Atlantic Bluefin Tuna

Abstract Field studies to investigate the survey capability of a 500-kHz multibeam sonar to monitor and quantify Atlantic bluefin tuna were undertaken at several fishing locations (commercial and recreational) off Prince Edward Island and at a grow-out pen in Nova Scotia. The results demonstrate that individual bluefin can be detected, enumerated, and tracked acoustically within the swathe of the sonar. Bluefin were observed individually, and in groups ranging from 2 to 16 fish. Schooling tuna, assumed to be foraging, were observed moving in a soldier formation. Estimates of in situ swimming speeds (0.5–11.0 m s−1) were made by tracking individual fish within the swathe. The mean interspatial distance between fish when swimming in a group of two or more tuna was estimated to be 8.94 m with a range of 2.68–22.63 m. Groups of up to 48 bluefin were observed aggregating around active herring gillnet vessels. Dorsal aspect target strength estimates of bluefin, obtained from an accompanying 120-kHz echosounder (Simrad EK60), ranged from −33 to −14 dB for fish from 220 to 313 cm (size estimated from commercial catches). Sonar detection ranges were dependent upon sea state and water depth. In rough seas, the surface layer became too turbulent, and air bubble attenuation too high, to consistently separate reverberation from fish-like targets. In shallow water (20–30 m), a range setting of >50 m could not be utilized due to seabed reflections. In water depths >50–60 m, a tilt angle of 7.5o below the horizontal allowed the sonar's range of up to 150 m to be utilized with minimal reverberation from the surface and seabed. The results indicate there is potential for using a 500-kHz multibeam sonar in fishery-independent surveys to monitor and to quantify bluefin in shallow water (<100 m).

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 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.

scholarly journals In situ swimming speed and swimming behaviour of fish feeding on the krill Meganyctiphanes norvegica

2005 ◽  
Vol 62 (8) ◽  
pp. 1822-1832 ◽  
Author(s):  
M SR Onsrud ◽  
S Kaartvedt ◽  
M T Breien
Keyword(s):  
Target Tracking ◽  
Water Column ◽  
Swimming Speed ◽  
Original Data ◽  
Clupea Harengus ◽  
Swimming Behaviour ◽  
Fish Feeding ◽  
Sea Bottom ◽  
Acoustic Target

In situ swimming speed and swimming behaviour of dielly migrating planktivorous fish were studied at a 120-m-deep location. Acoustic target tracking was performed using a hull-mounted transducer and submersible transducers located on the sea bottom and free hanging in the water column. The original data displayed a relationship between distance to transducer and swimming speed. A simplistic smoother applied during post-processing, appeared to break this relationship. Target tracking thus provided robust results on in situ swimming behaviour throughout the water column. Swimming speeds of deep-living fish, mainly Norway pout (Trisopterus esmarkii) and whiting (Merlangius merlangus), were highest during the day (speeds centred around 14–16 cm·s–1) and decreased somewhat by night (modes around 10–11 cm·s–1). Fish in the upper 10–30 m swam somewhat faster (speeds ranging from 16 to 24 cm·s–1). Fish in the upper layer at night were mainly Atlantic herring (Clupea harengus), sprat (Sprattus sprattus), and whiting. We ascribe the reduction of swimming speed in deep-living fish at night to a switch from visual feeding during daytime to nonvisual feeding by night. We suggest that shallow-living fish could forage visually even by night. Most tracks were fairly short, but some long tracks unveiled elaborate swimming paths as well as cyclic swimming behaviour.

scholarly journals In situ target strength estimates of visually verified orange roughy

2012 ◽  
Vol 70 (1) ◽  
pp. 215-222 ◽  
Author(s):  
Gavin J. Macaulay ◽  
Rudy J. Kloser ◽  
Tim E. Ryan
Keyword(s):  
Confidence Interval ◽  
Video Camera ◽  
Target Strength ◽  
Orange Roughy ◽  
Camera System ◽  
The Mean ◽  
Intractable Problem ◽  
Video Camera System ◽  
Fish Avoidance

Abstract Macaulay, G. J., Kloser, R. J., and Ryan, T. E. 2013. In situ target strength estimates of visually verified orange roughy. – ICES Journal of Marine Science, 70:215–222. The first estimates of orange roughy (Hoplostethus atlanticus) target strength at 38 and 120 kHz with visual verification were obtained from a self-contained echosounder and video camera system affixed to a demersal trawl towed through dense aggregations of spawning orange roughy. Mean target strength estimates were obtained from 24 tracks of orange roughy containing 83 echoes. The mean target strength at 38 kHz was –52.0 dB with a 95% confidence interval of –53.3 to –50.9 dB for fish with a mean length of 33.9 cm. At 120 kHz the mean target strength was –47.9 dB (confidence interval of –48.8 to –46.4 dB). This work makes two significant advances: in situ TS measurements have been made that can be confidently attributed to orange roughy, and using a trawl to herd orange roughy past the system resolved the previously intractable problem of fish avoidance.

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.

scholarly journals Modelling the acoustic effect of swimbladder compression in herring

2003 ◽  
Vol 60 (3) ◽  
pp. 548-554 ◽  
Author(s):  
Natalia Gorska ◽  
Egil Ona
Keyword(s):  
Orientation Distribution ◽  
Target Strength ◽  
Acoustic Effect ◽  
Acoustic Backscattering ◽  
Cylinder Model ◽  
Acoustic Surveys ◽  
The Mean ◽  
Theoretical Results

Abstract Obtaining accurate data on fish target strength (TS) is important when determining the quality of the results from acoustic surveys. However, this requires an improved understanding of both behavioural and environmental influences on the acoustic backscattering by fish. It is well known that the increased pressure with depth compresses the swimbladder of herring, and it has been confirmed by in situ measurements that the TS of adult herring (30–34 cm) is 3–5 dB weaker at 300 m than that of fish close to the surface. Understanding exactly how swimbladder compression may influence herring TS is, therefore, of great interest, and is the main motivation behind this study. Taking account of swimbladder volume changes with depth, we obtained analytical solutions using the Modal-Based, Deformed-Cylinder Model (MB-DCM). The mean-backscattering cross-section is then computed with selected orientation patterns, length distributions, and contrast parameters. The depth-dependence of TS at different acoustic frequencies has been studied. We conducted a sensitivity analysis to show how TS is dependent on the contraction rates of the bladder dimensions and on the fish-orientation distribution. Our theoretical results are compared with TS measured at 38 kHz.

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