scholarly journals On the target strength of Baltic clupeids

2009 ◽  
Vol 66 (6) ◽  
pp. 1184-1190 ◽  
Author(s):  
Sascha M. M. Fässler ◽  
Natalia Gorska
Keyword(s):  
Target Strength ◽  
Biomass Estimation ◽  
Spatial And Temporal Variability ◽  
Important Species ◽  
Acoustic Frequency ◽  
Acoustic Backscattering ◽  
Baltic Herring ◽  
Fish Morphology ◽  
The Baltic ◽  
Relationship Of

Abstract Fässler, S. M. M., and Gorska, N. 2009. On the target strength of Baltic clupeids. – ICES Journal of Marine Science, 66: 1184–1190. The acoustic backscattering of Baltic clupeids, herring and sprat, is explored to improve biomass estimation of these ecologically and commercially important species. Modelling approaches that account for the complexity of fish morphology are used to compute the mean backscattering cross section. The input data for modelling are based on X-ray radiographs of Baltic herring and sprat. The backscatter sensitivity to fish morphology and to other biological (fat content), acoustic (frequency), behavioural (orientation pattern), and environmental (depth and salinity) parameters is also analysed. The effect of various parameters on the TS–L relationship of Baltic clupeids is studied, and the possibility of using the same TS–L relationships for Baltic herring and sprat is discussed. The results improve the understanding of the spatial and temporal variability of the measured target strength of clupeids in the Baltic Sea.

scholarly journals Validation of the stochastic distorted-wave Born approximation model with broad bandwidth total target strength measurements of Antarctic krill

2003 ◽  
Vol 60 (3) ◽  
pp. 625-635 ◽  
Author(s):  
David A. Demer ◽  
Stéphane G. Conti
Keyword(s):  
Born Approximation ◽  
Antarctic Krill ◽  
Target Strength ◽  
Biomass Estimation ◽  
Distorted Wave ◽  
Distorted Wave Born Approximation ◽  
Sound Scattering ◽  
Important Species ◽  
Field Station ◽  
Broad Bandwidth

Abstract Total-scattering cross-sections (σt) of Antarctic krill (Euphausia superba) were measured over a broad bandwidth (36–202 kHz) using a new technique based on acoustical reverberation in a cavity. From 18 February to 9 March 2002, mean total target strengths (TTS = 10 log(σt/4π)), were measured from groups of 57–1169 krill (average standard length=31.6 mm; standard deviation=6.6 mm) at the Cape Shirreff field station, Livingston Island, Antarctica, and aboard RV “Yuzhmorgeologiya”. Chirp pulses were transmitted sequentially by an omni-directional emitter into one of three glass carboys containing groups of krill swimming in 9.3, 19.3, or 45.9 liters of seawater (0.6°C≤temperature≤4.0°C). Between each pulse the krill moved within the fixed-boundary tank and the modulated reverberations were sensed bi-statically with three omni-directional receivers. At each center frequency (fc), the coherent energy in 200-pulse ensembles identified sound scattered by the tank. The incoherent energy described total sound scattering from the krill. Thus, the TTS at each fc was extracted from a correlation analysis of energy reverberated in the tank. Measurement bias was determined to be ±0.4 dB from an experiment using metal sphere reference targets, and the precision was estimated as ±0.8 dB from the variability in the krill TTS (fc) measurements. The empirical estimates of mean σt corroborated a krill-scattering model based on the distorted-wave Born approximation (DWBA), enhanced by the authors to account for the stochastic nature of sound scattering (SDWBA), integrated over all scattering angles and averaged over all incident angles (SDWBATTS). The SDWBA, solved for target strength of Antarctic krill, may be the best predictor of backscatter for this important species and may also provide backscattering spectra for improving their acoustic identification. These advances may help to reduce uncertainty in krill-biomass estimation using multi-frequency echosounder data and echo-integration methods.

Analisis Akustik Target Strength Penyu Hijau (Chelonia Mydas) Melalui Pengukuran Secara Terkontrol Pada Frekuensi 200 kHz

2021 ◽  
Vol 3 (2) ◽  
pp. 94-108
Author(s):  
Teddy Julyansyah ◽  
Deddy Bakhtiar ◽  
Ari Anggoro
Keyword(s):  
Green Turtle ◽  
Population Decline ◽  
Chelonia Mydas ◽  
Total Body Length ◽  
Acoustic Method ◽  
Target Strength ◽  
Acoustic Backscattering ◽  
Total Length ◽  
In Captivity ◽  
Total Body

ABSTRACT Turtles are reptiles that live in the sea and are able to migrate over long distances along the Indian Ocean, Pacific Ocean and Southeast Asia. Currently the number of turtle populations in nature has greatly decreased. This population decline is caused by natural factors and human activities that endanger the population directly or indirectly. At this time the tagging set technique (ID tag code) is a method that is often used to detect the presence of turtles by attaching tags to female turtles who are landing to lay eggs on the beach or while in captivity or the discovery of the mother turtle by fishermen. One other method that can be used to detect the presence of turtles is to use the acoustic method. The purpose of this study was to analyze the characteristics of the acoustic backscattering energy of the green turtle (Chelonia mydes) and to analyze the relationship between target strength and total body length of the green turtle (Chelonia mydas). This research was conducted in the Tapak Paderi waters pond, Bengkulu City, in August-October 2020. The average target strength (TS) value for green turtles was -48.07 dB. Based on the regression equation, the value of determination (R2) obtained is 0.78. Where this value shows that the total length of the green turtle has an effect of 78% on the average target strength (TS) value, while for 22% it is caused by other factors such as body shape, environmental factors and other factors. Based on the ANOVA test, it can be concluded that there is a relationship between the total length and the value of the target strength (TS) on the green turtle or the value of the total length has an influence on the value of the target strength (TS) on the green turtle.  

Acoustic backscattering by Hawaiian lutjanid snappers. I. Target strength and swimbladder characteristics

2003 ◽  
Vol 114 (5) ◽  
pp. 2757 ◽  
Author(s):  
Kelly J. Benoit-Bird ◽  
Whitlow W. L. Au ◽  
Christopher D. Kelley
Keyword(s):  
Target Strength ◽  
Acoustic Backscattering

Estimating target strength of young chum salmon (Oncorhynchus keta)

2022 ◽  
pp. 1-5
Author(s):  
Kenji Minami ◽  
Hokuto Shirakawa ◽  
Yohei Kawauchi ◽  
Huamei Shao ◽  
Makoto Tomiyasu ◽  
...  
Keyword(s):  
Bering Sea ◽  
Chum Salmon ◽  
Fork Length ◽  
Target Strength ◽  
Oncorhynchus Keta ◽  
Biomass Estimation ◽  
Fishery Resource ◽  
Chum Salmon Oncorhynchus Keta ◽  
Acoustic Methods ◽  
The Bering Sea

Although chum salmon (Oncorhynchus keta) is an important fishery resource in Japan, acoustic methods cannot be applied to biomass estimation because the target strength (TS) is unknown. This study clarified the TS for each fork length (FL: 5.5–33.5 cm) of young chum salmon inhabiting the Japanese coastal area to the Bering Sea by measuring free-swimming fish. The size dependences of the TS values were TSmean = 20 log10 FL – 68.0, for both 38 and 120 kHz. This facilitated the estimation of biomass of young salmon using acoustic methods.

scholarly journals Effect of Different Acoustic Parameters on NOx Emissions of Partially Premixed Flame

2019 ◽  
Vol 9 (7) ◽  
pp. 1490 ◽  
Author(s):  
Kai Deng ◽  
Mingxiao Wang ◽  
Zhongliang Shen ◽  
Yanjun Hu ◽  
Yingjie Zhong
Keyword(s):  
Flame Length ◽  
Premixed Flame ◽  
Nox Emissions ◽  
Acoustic Parameters ◽  
Acoustic Frequency ◽  
Image Velocimetry ◽  
Proportional Relationship ◽  
Partially Premixed ◽  
Partially Premixed Flame ◽  
Relationship Of

The effects of acoustic frequency (f)/0–400 Hz and amplitude (A)/0–1400 Pa on nitrogen oxides (NOx) emissions of a partially premixed flame were investigated experimentally. The mechanism of NOx emissions was analyzed by the evolution of the vortex, which was shown by particle image velocimetry (PIV). From the relationship of NOx emission index (EINOx) and acoustic parameters, it was concluded that a critical frequency (fc) from 170 Hz to 190 Hz appeared. When the frequency was less than fc, EINOx decreased linearly with an increase in amplitude. The flame length became shorter, which led to a decrease in the global residence time, and hence, a reduction in reaction time for NOx. However, a direct proportional relationship between EINOx and amplitude was not found when the frequency was larger than fc. Based on PIV particle scattering images, with an increase of the acoustic frequency, the effects of the acoustic field on the flame base became less significant, but the flame length and reaction space of NOx were gradually increased.

scholarly journals Mapping Coastal Wetland Biomass from High Resolution Unmanned Aerial Vehicle (UAV) Imagery

2019 ◽  
Vol 11 (5) ◽  
pp. 540 ◽  
Author(s):  
Cheryl Doughty ◽  
Kyle Cavanaugh
Keyword(s):  
Salt Marsh ◽  
High Resolution ◽  
Aboveground Biomass ◽  
Vegetation Index ◽  
Coastal Wetland ◽  
Spatial Scales ◽  
Biomass Estimation ◽  
Spatial And Temporal Variability ◽  
Estimation Model ◽  
Spatial And Temporal Scales

Salt marsh productivity is an important control of resiliency to sea level rise. However, our understanding of how marsh biomass and productivity vary across fine spatial and temporal scales is limited. Remote sensing provides a means for characterizing spatial and temporal variability in marsh aboveground biomass, but most satellite and airborne sensors have limited spatial and/or temporal resolution. Imagery from unmanned aerial vehicles (UAVs) can be used to address this data gap. We combined seasonal field surveys and multispectral UAV imagery collected using a DJI Matrice 100 and Micasense Rededge sensor from the Carpinteria Salt Marsh Reserve in California, USA to develop a method for high-resolution mapping of aboveground saltmarsh biomass. UAV imagery was used to test a suite of vegetation indices in their ability to predict aboveground biomass (AGB). The normalized difference vegetation index (NDVI) provided the strongest correlation to aboveground biomass for each season and when seasonal data were pooled, though seasonal models (e.g., spring, r2 = 0.67; RMSE = 344 g m−2) were more robust than the annual model (r2 = 0.36; RMSE = 496 g m−2). The NDVI aboveground biomass estimation model (AGB = 2428.2 × NDVI + 120.1) was then used to create maps of biomass for each season. Total site-wide aboveground biomass ranged from 147 Mg to 205 Mg and was highest in the spring, with an average of 1222.9 g m−2. Analysis of spatial patterns in AGB demonstrated that AGB was highest in intermediate elevations that ranged from 1.6–1.8 m NAVD88. This UAV-based approach can be used aid the investigation of biomass dynamics in wetlands across a range of spatial scales.

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.

Seasonal variability of phytoplankton in the shallow waters of the southern Baltic Sea

2018 ◽  
Vol 33 (1) ◽  
pp. 9-15
Author(s):  
Iwona Zabroś ◽  
Marlena Mioskowska
Keyword(s):  
Baltic Sea ◽  
Temporal Distribution ◽  
Environmental Parameters ◽  
Spatial And Temporal Variability ◽  
Sample Collection ◽  
The Baltic Sea ◽  
Mean Values ◽  
Southern Baltic Sea ◽  
Southern Baltic ◽  
The Baltic

The Baltic Sea is characterized by a seasonal variation of phytoplankton structure. These organisms are particularly sensitive to changes in various environmental parameters. Cyclic, recurring annually fluctuation of species composition, abundance and biomass of phytoplankton is a consequence of these changes. Spatial and temporal variability of particular groups of phytoplankton is not the same in different areas of the Baltic Sea. The purpose of this work was to determine the spatial and temporal distribution of phytoplankton in three chosen areas of the coastal zone of the southern Baltic Sea (Ustka, Poddąbie and Rowy) in the period of November 2014 - September 2016. Mean values of abundance and biomass of phytoplankton for the surveyed areas were typical for this type of coastal waters. In each of the surveyed areas the same dominat species in terms of the abundance and biomass were observed. A growth of diatoms was recorded only in the area of Ustka, which could have been caused by the inflow of river waters. Seasonal surveys of phytoplankton indicated that in the case of the studies regarding this parameter – taxonomic composition, abundance and biomass in the same surveyed area were similar at the three research stations (e.g. 75-80%), depending on the season of the year. On this basis, it was concluded that, whether carrying out the monitoring of phytoplankton or planned investments, the sample collection frequency had a greater significance than the number of research stations.

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