Ex situ acoustic target strength by tilt angle and pulsation of moon jellyfish (Aurelia aurita) using frequency 70 kHz

2015 ◽  
Vol 51 (3) ◽  
pp. 295-301
Author(s):  
Eun–A YOON ◽  
Doo–Jin HWANG ◽  
HIROSE Miyuki ◽  
Kouichi SAWADA ◽  
Yoshiaki FUKUDA ◽  
...  
Keyword(s):  
Tilt Angle ◽  
Aurelia Aurita ◽  
Ex Situ ◽  
Target Strength ◽  
Moon Jellyfish ◽  
Acoustic Target

scholarly journals The influence of tilt angle on the acoustic target strength of the Japanese common squid (Todarodes pacificus)

2005 ◽  
Vol 62 (4) ◽  
pp. 779-789 ◽  
Author(s):  
Donhyug Kang ◽  
Tohru Mukai ◽  
Kohji Iida ◽  
Doojin Hwang ◽  
Jung-Goo Myoung
Keyword(s):  
Tilt Angle ◽  
Empirical Relationship ◽  
Ex Situ ◽  
Target Strength ◽  
Todarodes Pacificus ◽  
Common Squid ◽  
Acoustic Target ◽  
The Mean ◽  
Highly Correlated ◽  
Japanese Common Squid

Abstract To measure the influence of changes in tilt angle on the acoustic target strength (TS) of the Japanese common squid (Todarodes pacificus), we conducted a series of experiments to estimate TS in relation to tilt angle and swimming angle. Swimming angle was measured in a seawater tank using two infrared, underwater cameras under dark conditions. Ex situ measurements of TS in relation to tilt angle on live specimens using a fishhook and cage method were then conducted at 38 and 120 kHz; mantle length (ML) ranged from 21 to 27 cm (mean 24.75 cm). For the more precise TS measurement with tilt angle, another set of ex situ TS measurements relative to tilt angle was made at 38 and 120 kHz on tethered, anesthetized specimens in seawater. The mean swimming angle was −17.7° (±12.7° s.d.). The mean TS varied from −48.6 to −44.6 dB and was relatively higher at 120 kHz than at 38 kHz, in the order of 0.7 and 2.5 dB. The empirical relationship between TS (dB) and ML (cm) is given by TS = 20 log10(ML) − 75.4 (r = 0.81) at 38 kHz or TS = 20 log10(ML) − 73.5 (r = 0.64) at 120 kHz. Based on the tethered method for the anesthetized squid, the mean standardized TS values (b20) were found to be highly correlated with the tilt angle, and the resultant fitted equations for b20 were expressed as: b20 = −73.3 + 0.48 × Θ + 0.0122 × Θ2 + 0.00016 × Θ3 for 38 kHz and b20 = −72.6 + 0.53 × Θ + 0.0134 × Θ2 + 0.00014 × Θ3 for 120 kHz, where Θ is the negative tilt angle in degrees. The mean TS based on the measurements using live squid was higher than that of tethered measurements, i.e., 2.6 dB at 38 kHz and 4.0 dB at 120 kHz. The higher mean TS in the ex situ measurements for the live squid can be explained by the influence of the low tilt angle on the overall TS data. The results can be used to understand the influence of tilt angle on the TS of Todarodes pacificus and thus improve the accuracy of biomass estimates.

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 effects of swimbladder size, condition and gonads on the acoustic target strength of mature capelin

2003 ◽  
Vol 60 (5) ◽  
pp. 1056-1062 ◽  
Author(s):  
Roar Jørgensen
Keyword(s):  
Tilt Angle ◽  
Barents Sea ◽  
Condition Factor ◽  
Target Strength ◽  
Gonad Weight ◽  
The Barents Sea ◽  
Size Condition ◽  
Negative Effect ◽  
Acoustic Target ◽  
Post Spawning

Abstract Pre- and post-spawning capelin from the Barents Sea stock were observed in a net pen with a calibrated 38 kHz scientific split-beam echosounder. The transducer was positioned vertically or tilted. The acoustic target strength (TS) of capelin depended on swimbladder length. In female capelin within 15.5–18.0 cm length the logarithm of weight was significantly negatively related to TS. The negative effect of weight on TS could be due to a higher condition factor (assumed higher fat content), which gave the fish additional buoyancy and less need for swimbladder volume. The effect of gonad weight on TS was not significant. Comparisons of measurements made with vertical and tilted transducers demonstrated a small but significant effect of tilt angle on TS.

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.

scholarly journals Estimates of acoustic target strength for giant jellyfish Nemopilema nomurai Kishinouye in the coastal Northwest Pacific

2013 ◽  
Vol 71 (3) ◽  
pp. 597-603 ◽  
Author(s):  
Donhyug Kang ◽  
Jusam Park ◽  
Seom-Kyu Jung ◽  
Sungho Cho
Keyword(s):  
Acoustic Scattering ◽  
Ex Situ ◽  
Target Strength ◽  
Northwest Pacific ◽  
Bell Diameter ◽  
Least Squares Regression ◽  
Acoustic Measurements ◽  
Nemopilema Nomurai ◽  
Acoustic Target ◽  
Giant Jellyfish

Abstract Acoustic target strength (TS) measurements were made of ex situ giant jellyfish Nemopilema nomurai Kishinouye at 38 and 120 kHz. These TS data may be useful for developing acoustic scattering models, and surveying giant jellyfish distributions and biomasses. Each jellyfish was tethered in seawater using a monofilament line that vertically penetrated its bell's centre. During the acoustic measurements, an underwater video camera was used to continuously monitor the jellyfish's behaviour. Acoustic measurements were made using split-beam transducers. TS measurements were made of 27 individual jellyfish, but data were analysed for 23 specimens (bell diameter in air, Dair = 21–65 cm) at 38 kHz, and 19 specimens (Dair = 21–46 cm) at 120 kHz, respectively. Least-squares regression fits of TS vs. log(Dair) were TS38kHz = 20•log10Dair–82.7 (r = 0.76) and TS120kHz = 20•log10Dair–86.7 (r = 0.79). The mean TS values at 38 and 120 kHz, using the average Dair = 40.3 cm and 35.5 cm, respectively, were −50.6 and −55.7 dB. The reduced TS, a function of the ratio of Dair to wavelength (λ), was RTS(Dair/λ) = −6.1•log10(Dair/λ) –36.1 (r = 0.51). These RTS values decreased with increasing Dair/λ. Symbiotic medusa shrimp (Latreutes anoplonyx Kemp) contributed negligible bias to our TS measurements of giant jellyfish. These ex situ TS measurements may be used in acoustic surveys to estimate the distributions and biomasses of N. nomurai.

scholarly journals Side-aspect target-strength measurements of bay anchovy (Anchoa mitchilli) and Gulf menhaden (Brevoortia patronus) derived from ex situ experiments

2008 ◽  
Vol 65 (6) ◽  
pp. 1012-1020 ◽  
Author(s):  
Kevin M. Boswell ◽  
Charles A. Wilson
Keyword(s):  
Pulse Duration ◽  
Linear Models ◽  
Ex Situ ◽  
Target Strength ◽  
Species Variation ◽  
Anchoa Mitchilli ◽  
Pooled Data ◽  
Acoustic Target ◽  
Brevoortia Patronus ◽  
Bay Anchovy

Abstract Boswell, K. M., and Wilson, C. A. 2008. Side-aspect target strength measurements of bay anchovy (Anchoa mitchilli) and Gulf menhaden (Brevoortia patronus) derived from ex situ experiments. – ICES Journal of Marine Science, 65: 1012–1020. Acoustic target strengths (TSs) of bay anchovy [Anchoa mitchilli, 4.7–6.1 cm TL (total length)] and Gulf menhaden (Brevoortia patronus, 5.1–7.7 cm TL) were measured at 420 kHz during side-aspect, ex situ experiments. TS–TL relationships were derived at aspect for tethered individuals, and TS distributions were compared with those of free-swimming fish. Linear models relating TS and TL were fitted to data at two levels of pulse duration (0.1 and 0.4 ms) for both side aspect and all horizontal aspects of each species, and for pooled data from both species. At a pulse duration of 0.4 ms, the side-aspect TS–TL relationships were anchovy: TSlateral = 19.5 log10 TLcm − 62.4; menhaden: TSlateral = 26.1 log10 Lcm − 65.6; pooled: TSlateral = 32 log10 TLcm − 70.9. For all horizontal-aspect orientations (0–180° in the horizontal) the best-fit TS–TL relationships were anchovy: TSall = 20 log10 TLcm− 65.4; menhaden: TSall = 20 log10 TLcm − 64.8; pooled: TSall = 20 log10 TLcm− 65. However, the “fit” for all angles was consistently low. Predicted TS comparisons with side-aspect models presented by earlier authors suggested biases in the estimated TL. Additionally, relationships between TS and wet weight (W) were derived for each species. Variation in TS by pulse-duration level suggests the potential for the use of this factor as a time-dependent variable by which to separate echoes from bay anchovy and Gulf menhaden.

scholarly journals Target strength and tilt-angle distribution of the lesser sandeel (Ammodytes marinus)

2012 ◽  
Vol 69 (6) ◽  
pp. 1099-1107 ◽  
Author(s):  
Rokas Kubilius ◽  
Egil Ona
Keyword(s):  
Tilt Angle ◽  
Field Experiments ◽  
Video Camera ◽  
Target Strength ◽  
Fish Length ◽  
Angle Distribution ◽  
Total Uncertainty ◽  
Sea Bottom ◽  
Swimming Pattern ◽  
Acoustic Target

Abstract Kubilius, R., and Ona, E. 2012. Target strength and tilt-angle distribution of lesser sandeel (Ammodytes marinus) – ICES Journal of Marine Science, 69: 1099–1107. North Sea stocks of lesser sandeel have recently become depleted, and improved methods for abundance estimation are sought. This paper focuses on the acoustic target strength (TS) and orientation of sandeel, measured simultaneously in several field experiments. A specially designed cubic cage, fitted with an echosounder and a video camera, was lowered onto the sea bottom, trapping wild sandeel inside. Methods for manually selecting valid echotraces from individual sandeel are described. Scattered mean TS values from several experiments are reported. These are, in spite of the observed variability, summarized in a TS–fish length (cm) relationship as TS = 20logL – 93.1 (dB) at 200 kHz. We believe that the accuracy of the relationship may still be debated; incorporating larger uncertainty in the overall mean TS will increase the total uncertainty of the stock biomass estimate from sandeel acoustic surveys. This uncertainty is now, using standard narrow-beam echosounders, dominated by the fish patchiness relative to the survey coverage. Results from pilot investigations of the sandeel swimming orientation using video cameras are also presented, showing that sandeel usually has an anguilliform swimming pattern with substantial positive (head-up) tilt. The spread of the tilt-angle distribution is also larger than for more neutrally buoyant fishes.

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