Response of Biological Acoustic Backscattering to Ships' Lights

1985 ◽  
Vol 42 (9) ◽  
pp. 1535-1543 ◽  
Author(s):  
D. Sameoto ◽  
N. A. Cochrane ◽  
A. W. Herman
Keyword(s):  
Nova Scotia ◽  
Continental Shelf ◽  
Sea Surface ◽  
Target Strength ◽  
Acoustic Response ◽  
Strong Response ◽  
Acoustic Backscattering ◽  
Back Scattering ◽  
Biological Sampling ◽  
Scattering Strength

The response of zooplankton (copepods and euphausiids) and micronekton (myctophids) to ships' lights was quantitatively assessed in terms of the acoustic backscattering from these organisms under controlled sea surface illumination. Two frequencies, 51 and 198 kHz, were utilized. No acoustic response to light on stations off the edge of the Nova Scotia continental shelf was found but a strong response on the shelf was observed. The response at both frequencies consisted of a nearly instantaneous drop in volume back-scattering strength by as much as 20 dB in the top 60 m. Biological sampling tentatively suggested that the organisms responsible were euphausiids and that a sudden geometric reorientation when the light was turned on resulted in a drop in their target strength.

scholarly journals ACOUSTIC CLASSIFICATION OF FRESHWATER FISH SPECIES USING ARTIFICIAL NEURAL NETWORK: EVALUATION OF THE MODEL PERFORMANCE

2013 ◽  
Vol 19 (1) ◽  
pp. 19
Author(s):  
Zulkarnaen Fahmi ◽  
Wijopriono Wijopriono
Keyword(s):  
Neural Network ◽  
Artificial Neural Network ◽  
Fish Species ◽  
Back Propagation ◽  
Model Performance ◽  
Target Strength ◽  
Multi Layer Perceptron ◽  
Back Scattering ◽  
Artificial Neural ◽  
Scattering Strength

Hydroacoustic techniques are a valuable tool for the stock assessments of many fish species. Nonetheless, such techniques are limited by problems of species identification. Several methods and techniques have been used in addressing the problem of acoustic identification species and one of them is Artificial Neural Networks (ANNs). In this paper, Back propagation (BP) and Multi Layer Perceptron (MLP) of the Artificial Neural Network were used to classify carp (<em>Cyprinus carpio</em>), tilapia (<em>Oreochromis niloticus</em>), and catfish (<em>Pangasius hypothalmus</em>). Classification was done using a set of descriptors extracted from the acoustic data records, i.e. Volume Back scattering (Sv), Target Strength (TS), Area Back scattering Strength, Skewness, Kurtosis, Depth, Height and Relative altitude. The results showed that the Multi Layer Perceptron approach performed better than the Back propagation. The classification rates was 85.7% with the multi layer perceptron (MLP) compared to 84.8% with back propagation (BP) ANN.

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

scholarly journals Seasonal trends and phenology shifts in sea surface temperature on the North American northeastern continental shelf

Elem Sci Anth ◽  
2017 ◽  
Vol 5 ◽  
Author(s):  
Andrew C. Thomas ◽  
Andrew J. Pershing ◽  
Kevin D. Friedland ◽  
Janet A. Nye ◽  
Katherine E. Mills ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Continental Shelf ◽  
Sea Surface Temperature ◽  
North American ◽  
Gulf Of Maine ◽  
Sea Surface ◽  
Scotian Shelf ◽  
Seasonal Differences ◽  
Study Region ◽  
The North

The northeastern North American continental shelf from Cape Hatteras to the Scotian Shelf is a region of globally extreme positive trends in sea surface temperature (SST). Here, a 33-year (1982–2014) time series of daily satellite SST data was used to quantify and map spatial patterns in SST trends and phenology over this shelf. Strongest trends are over the Scotian Shelf (&gt;0.6°C decade–1) and Gulf of Maine (&gt;0.4°C decade–1) with weaker trends over the inner Mid-Atlantic Bight (~0.3°C decade–1). Winter (January–April) trends are relatively weak, and even negative in some areas; early summer (May–June) trends are positive everywhere, and later summer (July–September) trends are strongest (~1.0°C decade–1). These seasonal differences shift the phenology of many metrics of the SST cycle. The yearday on which specific temperature thresholds (8° and 12°C) are reached in spring trends earlier, most strongly over the Scotian Shelf and Gulf of Maine (~ –0.5 days year–1). Three metrics defining the warmest summer period show significant trends towards earlier summer starts, later summer ends and longer summer duration over the entire study region. Trends in start and end dates are strongest (~1 day year–1) over the Gulf of Maine and Scotian Shelf. Trends in increased summer duration are &gt;2.0 days year–1 in parts of the Gulf of Maine. Regression analyses show that phenology trends have regionally varying links to the North Atlantic Oscillation, to local spring and summer atmospheric pressure and air temperature and to Gulf Stream position. For effective monitoring and management of dynamically heterogeneous shelf regions, the results highlight the need to quantify spatial and seasonal differences in SST trends as well as trends in SST phenology, each of which likely has implications for the ecological functioning of the shelf.

Present-Day Methods of Depth Measurement

2000 ◽  
Author(s):  
John Hughes Clarke
Keyword(s):  
Continental Shelf ◽  
Traditional Approach ◽  
Acoustic Pulse ◽  
Acoustic Energy ◽  
Sea Surface ◽  
Optimal Method ◽  
Single Beam ◽  
Bathymetric Data ◽  
Incomplete Coverage

Bathymetric data are needed to derive the morphological criteria that define the extent of the juridical continental shelf. Two features in particular, the '"foot of slope" and the 2500-m contour, must be defined. The previous chapter considered historical methods of determining bathymetry. This chapter will cover the present day methods that can be used to better meet the need for accurate bathymetry. In order to satisfy the demands of UNCLOS, bathymetric data are required in depths ranging from about 200 m to more than 5000 m. Shallower depths, while useful for demonstrating the morphology of the physical continental shelf, do not bear any relevance to the delineation of juridical continental shelf boundaries, other than where they are required to establish the baseline. Alternate methods to derive bathymetry other than using sound are available. Those involving airborne electromagnetic methods (e.g., electromagnetic induction, red-green lasers, and inversion of sea surface radar images) are not capable of determining depths much in excess of 40 m. The only other method potentially useful for deriving deeper water bathymetry is through inversion of sea surface altimetry obtained from satellites. This will be discussed at the end of this chapter. The optimal method thus remains acoustic. The traditional approach has been to use single-beam echo sounders (see previous chapter). This chapter discusses the more modern '"swath" sonar techniques, which are becoming widely used. The great majority of historic bathymetry has been collected using the single-beam sounding approach. As discussed in chapter 9, this method has a number of limitations, three of the most critical of which are i. incomplete coverage; ii. uncertainty about the exact location of the first arrival of the acoustic pulse; and iii. distortion of short-wavelength topography. In order to achieve more complete coverage, better echo location, and higher spatial resolution, methods were devised to project acoustic energy both within narrower solid angles (figure 10.1) and while deriving this information over angular sectors extending further out from the side of the survey vessel. All the methods commonly applied involved scanning the seabed orthogonal to the ship heading. Sequential scans, accumulated as the ship progresses, form a corridor (or swath) of seabed information (figure 10.2).

scholarly journals New broadband methods for resonance classification and high-resolution imagery of fish with swimbladders using a modified commercial broadband echosounder

2010 ◽  
Vol 67 (2) ◽  
pp. 365-378 ◽  
Author(s):  
Timothy K. Stanton ◽  
Dezhang Chu ◽  
J. Michael Jech ◽  
James D. Irish
Keyword(s):  
High Resolution ◽  
Pulse Compression ◽  
Target Strength ◽  
Compression Technique ◽  
Range Resolution ◽  
High Resolution Imagery ◽  
Broadband Signal ◽  
Scattering Strength ◽  
Broadband Signal Processing ◽  
Lower Frequencies

Abstract Stanton, T. K., Chu, D., Jech, J. M., and Irish, J. D. 2010. New broadband methods for resonance classification and high-resolution imagery of fish with swimbladders using a modified commercial broadband echosounder. – ICES Journal of Marine Science, 67: 365–378. A commercial acoustic system, originally designed for seafloor applications, has been adapted for studying fish with swimbladders. The towed system contains broadband acoustic channels collectively spanning the frequency range 1.7–100 kHz, with some gaps. Using a pulse-compression technique, the range resolution of the echoes is ∼20 and 3 cm in the lower and upper ranges of the frequencies, respectively, allowing high-resolution imaging of patches and resolving fish near the seafloor. Measuring the swimbladder resonance at the lower frequencies eliminates major ambiguities normally associated with the interpretation of fish echo data: (i) the resonance frequency can be used to estimate the volume of the swimbladder (inferring the size of fish), and (ii) signals at the lower frequencies do not depend strongly on the orientation of the fish. At-sea studies of Atlantic herring demonstrate the potential for routine measurements of fish size and density, with significant improvements in accuracy over traditional high-frequency narrowband echosounders. The system also detected patches of scatterers, presumably zooplankton, at the higher frequencies. New techniques for quantitative use of broadband systems are presented, including broadband calibration and relating target strength and volume-scattering strength to quantities associated with broadband signal processing.

The herring swimbladder: loss and gain of gas

1984 ◽  
Vol 64 (2) ◽  
pp. 441-459 ◽  
Author(s):  
J. H. S. Blaxter ◽  
R. S. Batty
Keyword(s):  
Pressure Vessel ◽  
Atmospheric Pressure ◽  
Juvenile Fish ◽  
Gas Diffusion ◽  
Sea Surface ◽  
Target Strength ◽  
Experimental Conditions ◽  
Neutral Buoyancy ◽  
Sea Bed ◽  
Ecological Implications

The herring is a physostome with no gas secretion mechanism in the swimbladder. The swimbladder volume was measured in fish from about 3–33 cm in length. It was rarely large enough to give the fish neutral buoyancy at the sea surface. Swimbladder volumes were also measured after periods of up to 1 week at pressures from 1·9 to 5·5 ATA (0·9–4·5atm above atmospheric pressure) in a laboratory pressure vessel and in a sub-surface cage in the sea. The swimbladder gas was lost within a few hours in the larval herring and in a few days in smaller juvenile fish; no change was found in older fish under experimental conditions. The findings were in accord with measurements of the guanine content of the swimbladder wall which was low in those fish which lost gas quickly. This supports the view that gas diffusion is limited by guanine crystals. While it seems likely that larger fish can exist for several weeks without the need to replenish the swimbladder gas some large spawning herring were caught at sea with empty swimbladders, suggesting a long stay near the sea bed. Analysis of swimbladder gas showed that oxygen tended to diffuse out more quickly than nitrogen. Behaviour experiments showed that fish with artificially emptied swimbladders could refill them by swallowing air at the surface, in some cases very quickly and efficiently. Fish with empty swimbladders and no access to the surface suffered a high mortality. The ecological implications of these results and their relevance to the interpretation of sonar ‘target strength’ measurements are discussed.

Estimating summer sea surface pCO2 on a river-dominated continental shelf using a satellite-based semi-mechanistic model

2019 ◽  
Vol 225 ◽  
pp. 115-126 ◽  
Author(s):  
Chengfeng Le ◽  
Yiyang Gao ◽  
Wei-Jun Cai ◽  
John C. Lehrter ◽  
Yan Bai ◽  
...  
Keyword(s):  
Continental Shelf ◽  
Mechanistic Model ◽  
Sea Surface
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