scholarly journals Comparing the modelled and measured target-strength variability of walleye pollock, Theragra chalcogramma

2004 ◽  
Vol 61 (3) ◽  
pp. 363-377 ◽  
Author(s):  
Elliott L. Hazen ◽  
John K. Horne
Keyword(s):  
Ex Situ ◽  
Target Strength ◽  
Physical Factors ◽  
Fish Length ◽  
Acoustic Frequency ◽  
Backscatter Intensity ◽  
Model Predictions ◽  
Strength Variability ◽  
Boyle’S Law ◽  
Insight Into

Abstract Many biological and physical factors potentially affect target strength. While these sources have been identified, few studies have compared the relative effects of individual factors. Modelled and measured target strengths in non-dimensional metrics were used to compare and rank the effects of fish length, tilt, depth, and acoustic frequency on backscatter intensity. Ex situ measurements of target strength were used to examine the effects of tilt and depth and then compared to backscatter model predictions. Swimbladder volume reduction due to increasing pressure at depth was modelled using Boyle's law and by varying the ratio of dorsal to lateral compression. We found that length has the largest effect on the modelled and measured backscatter intensity, followed by tilt, frequency, and depth. Including tilt distributions in backscatter estimates improved the match between empirical target-strength measures and model predictions. Non-dimensional influence ratios provide insight into the sources and magnitudes of the backscatter variability.

scholarly journals Measurements of acoustic-scattering spectra from the whole and parts of Atlantic mackerel

2009 ◽  
Vol 66 (6) ◽  
pp. 1169-1175 ◽  
Author(s):  
Tonje Lexau Nesse ◽  
Halvor Hobæk ◽  
Rolf J. Korneliussen
Keyword(s):  
Frequency Response ◽  
Acoustic Scattering ◽  
Ex Situ ◽  
Target Strength ◽  
Model Parameters ◽  
Acoustic Frequency ◽  
Atlantic Mackerel ◽  
Scattering Spectra ◽  
Laboratory Tank

Abstract Nesse, T. L., Hobæk, H., and Korneliussen, R. J. 2009. Measurements of acoustic-scattering spectra from the whole and parts of Atlantic mackerel. – ICES Journal of Marine Science, 66: 1169–1175. Atlantic mackerel (Scomber scombrus) are weak sound scatterers compared with fish that have swimbladders. Accurate acoustic estimates of mackerel abundance require estimates of target strength. Different parts of mackerel may dominate the backscattering spectra. Mackerel schools are acoustically recognized mainly by backscatter four times stronger at 200 kHz than at 38 kHz. Simulations have established that backscatter from only the flesh and the backbone could explain this frequency response, although there are uncertainties in the model parameters and simplifications. In this paper, experiments conducted in a laboratory tank to investigate the complexity of mackerel backscatter are discussed. Acoustic backscatter was measured over the frequency range 65–470 kHz from individual dead mackerel, and their backbones, heads, and skulls. Backscatter from the backbones was measured at several angles of incidence. Grating lobes (Bragg scattering) appeared at different angles, depending on the acoustic frequency and the spacing of the vertebrae. These lobes were evident in backbone backscatter after propagating through the flesh and can be used, in principle, to determine mackerel size acoustically. The frequency response of individual, ex situ Atlantic mackerel estimated from these measurements did not match that from the measurements of in situ mackerel schools. Further investigation is warranted.

scholarly journals A method for evaluating the effects of biological factors on fish target strength

2003 ◽  
Vol 60 (3) ◽  
pp. 555-562 ◽  
Author(s):  
Elliott L Hazen ◽  
John K Horne
Keyword(s):  
Target Strength ◽  
Comparative Approach ◽  
Theragra Chalcogramma ◽  
Fish Length ◽  
Biological Factors ◽  
Backscatter Intensity ◽  
Relative Contribution ◽  
Walleye Pollock Theragra Chalcogramma ◽  
Improving Accuracy ◽  
The Relationship

Abstract Understanding the relationship between fish biology and target strength potentially improves the accuracy of acoustic assessments. The effects of individual biological factors (e.g., length, tilt, and depth) on backscatter amplitude have been examined, but the relative contribution of each factor has not been quantified. Dimensionless ratios, which facilitate comparison of disparate quantities, were used to evaluate the effects of individual biological factors on echo intensities. Ratios from 25 adult walleye pollock (Theragra chalcogramma) were calculated using a Kirchhoff-ray-mode, backscatter model parameterized for each fish. This comparative approach can be used to identify the influence of biological factors on backscatter intensity and is potentially a tool for improving accuracy when converting acoustic size to fish length.

Comparison of in situ, ex situ, and backscatter model estimates of Pacific hake (Merluccius productus) target strength

2007 ◽  
Vol 64 (12) ◽  
pp. 1781-1794 ◽  
Author(s):  
Mark J Henderson ◽  
John K Horne
Keyword(s):  
Acoustic Energy ◽  
Common Method ◽  
Ex Situ ◽  
Target Strength ◽  
Fish Density ◽  
Fish Length ◽  
Merluccius Productus

To convert acoustic energy into estimates of fish density, the target strength (TS) of a representative fish must be known. TS is a measure of the acoustic reflectivity of a fish, which is variable depending on the presence of a swimbladder, the size of the fish, its behavior, morphology, and physiology. The most common method used to estimate the TS of a fish is a TS-to-length empirical regression, with TS values increasing with fish length. This study uses in situ and ex situ TS measurements and a backscatter model to develop TS-to-length conversions for Pacific hake (Merluccius productus). Results from in situ and ex situ measurements had regression intercepts 4–6 dB lower than the previous Pacific hake TS-to-length regression. These differences suggest that an individual hake reflects 2.5–4 times less acoustic energy than was previously estimated.

scholarly journals Ex situ target strength of rockfish (Sebastes schlegeli) and red sea bream (Pagrus major) in the Northwest Pacific

2003 ◽  
Vol 60 (3) ◽  
pp. 538-543 ◽  
Author(s):  
Donhyug Kang ◽  
Doojin Hwang
Keyword(s):  
Red Sea ◽  
Ex Situ ◽  
Sea Bream ◽  
Target Strength ◽  
Northwest Pacific ◽  
Fish Length ◽  
Sebastes Schlegeli ◽  
Red Sea Bream ◽  
Pagrus Major ◽  
Dual Beam

Abstract This study determined the ex situ target strength (TS) of rockfish (Sebastes schlegeli) and red sea bream (Pagrus major) in an artificial seawater tank as a means of helping to estimate fishery resources in coastal areas. TS experiments were conducted at frequencies of 38 kHz (split beam), 120 kHz (split beam), and 200 kHz (dual beam). The species were examined under two conditions: first, live fish confined to a small, net cage; and, second, as free-swimming fish inside a large tank. The study examined 21 rockfish and 20 red sea bream. The data were used to obtain expressions for TS against length and weight for the two species. The relationships between TS and fish length were as follows: for rockfish, TS38 kHz = 20 log10(L) − 67.7 (r = 0.80), TS120 kHz = 20 log10(L) − 74.3 (r = 0.61), TS200 kHz = 20 log10(L) − 72.8 (r = 0.41); and for red sea bream, TS38 kHz = 20 log10(L) − 66.8 (r = 0.86), TS120 kHz = 20 log10(L) − 74.0 (r = 0.65), TS200 kHz = 20 log10(L) − 74.1 (r = 0.83). The TS equations for rockfish and red sea bream as a function of fish weight at 38 kHz were TS38 kHz = 6.75 log10(W) − 56.0 (r = 0.78) and TS38 kHz = 4.08 log10(W) − 49.9 (r = 0.89), respectively. For comparison, calculations using the Helmholtz–Kirchhoff ray-approximation model based on swimbladder morphology were compared with the measured TS. When the tilt angle of the fish is zero, the mean TS from the model is 3–10 dB higher than the experimental results, although the maximum TS values were only 3–4 dB different.

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

2018 ◽  
Vol 8 (9) ◽  
pp. 1536 ◽  
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.

Motivation Configuration of Bluxury Tourism Behavior: An FsQCA Application

2021 ◽  
pp. 193896552110144
Author(s):  
Da Shi ◽  
Bowen Yi ◽  
Fangfang Shi ◽  
Simone Satta
Keyword(s):  
Comparative Analysis ◽  
Complexity Theory ◽  
Fuzzy Set ◽  
Qualitative Comparative Analysis ◽  
Complex Configuration ◽  
Physical Factors ◽  
Motivation Theory ◽  
Main Motivation ◽  
Push And Pull ◽  
Insight Into

This study investigates the motivation configuration of bluxury tourism behavior. According to complexity theory and push and pull motivation theory, we establish a framework of complex configuration conditions, including push forces, pull forces, and constraints that lead to bluxury tourism. Based on fuzzy-set qualitative comparative analysis, we identified seven main motivation configurations of bluxury tourism behavior covering three core factors: physical factors, seeking/exploration in push forces, and intangible factors in pull forces. In addition, combinations of constraints in the configuration demonstrate various paths leading to bluxury tourism behavior. These findings provide unique insight into bluxury tourism participation.

scholarly journals Acoustic Target Strength of the Endangered Chinese Sturgeon (Acipenser sinensis) by Ex Situ Measurements and Theoretical Calculations

2018 ◽  
Vol 8 (12) ◽  
pp. 2554 ◽  
Author(s):  
Hui Zhang ◽  
Junyi Li ◽  
Chongrui Wang ◽  
Chengyou Wang ◽  
Jinming Wu ◽  
...  
Keyword(s):  
Theoretical Calculations ◽  
Breeding Population ◽  
Ex Situ ◽  
Target Strength ◽  
Effective Management ◽  
Chinese Sturgeon ◽  
Acipenser Sinensis ◽  
Acoustic Target ◽  
The Mean ◽  
Db Difference

The Chinese sturgeon, Acipenser sinensis, is a large anadromous and highly endangered protected species. The assessment of its breeding population in the Yangtze River is critically important for effective management and population preservation. Currently, hydroacoustic methods have been widely used to study the adult sturgeons in the river, whereas the acoustic target strength (TS) characteristics of the species have not been studied. In this study, the TS of Chinese sturgeon was carefully evaluated both by ex situ measurements and theoretical calculations. Six Chinese sturgeons (Body Length (BL): 74.0−92.6 cm) were measured by a 199 kHz split echosounder in a 10-m deep net cage. The computed tomography of a Chinese sturgeon (BL: 110.0 cm) was conducted and the Kirchhoff ray mode (KRM) method was used to estimate the theoretical TS. As a result, the mean ex situ TS range of the six specimens was from −26.9 to −31.4 dB, which was very close to the KRM estimation (~1 dB difference). Then, the KRM method was used to predict the TS of Chinese sturgeon as a function of BL in six frequencies commonly used in freshwater environments and to estimate the TS of a representative adult Chinese sturgeon (250 cm) as a function of frequency and tilt angle. This study can provide a good basis for future hydroacoustic studies on the critically endangered Chinese sturgeon.

scholarly journals The influence of ontogeny, physiology, and behaviour on the target strength of walleye pollock (Theragra chalcogramma)

2003 ◽  
Vol 60 (5) ◽  
pp. 1063-1074 ◽  
Author(s):  
John K Horne
Keyword(s):  
Adult Life ◽  
Dorsal Surface ◽  
Walleye Pollock ◽  
Target Strength ◽  
Theragra Chalcogramma ◽  
Physical Factors ◽  
Biological Factors ◽  
Factors Associated ◽  
Surface Areas ◽  
Walleye Pollock Theragra Chalcogramma

Abstract Variability in echo intensities from aquatic organisms is caused by physical factors associated with the transmission of sound through water, and by biological factors associated with the ontogeny, physiology, and behaviour of targets. Acoustic-based density estimates depend on accurately characterizing reflected or backscattered sound from any species of interest. Digitized lateral and dorsal radiographs of walleye pollock (Theragra chalcogramma) were used to characterize intra-specific variability among young-of-the-year, juvenile, and adult life-history stages. Kirchhoff-ray mode (KRM) models were used to quantify variability in backscatter intensities at 38 and 120 kHz. At these geometric scattering frequencies, swimbladder surface areas influence echo intensities. Dorsal swimbladder surface areas were proportionate to fish lengths and decreased after fish were fed. Corresponding changes in backscatter were not proportionate to the reduction in dorsal surface area. The ratio of dorsal to lateral swimbladder surface areas was consistent among gravid and non-gravid fish. Walleye pollock tilt angles were centred at 90° and did not differ among densities or between light and dark cycles. Target strength–length regressions and KRM-predicted backscatter models closely matched in situ target-strength measurements for walleye pollock in the Bering Sea. Backscatter variability can be minimized through judicious deployment of equipment and equipment-parameter settings, but the relative influence of biological factors on backscatter amplitude has not been determined.

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