In situ measurement of target strength, tilt angle, and swimming speed of Boreopacific gonate squid (Gonatopsis borealis)

2006 ◽  
Vol 120 (5) ◽  
pp. 3107-3107 ◽  
Author(s):  
Kouichi Sawada ◽  
Hideyuki Takahashi ◽  
Koki Abe ◽  
Yoshimi Takao
Keyword(s):  
Tilt Angle ◽  
Swimming Speed ◽  
In Situ Measurement ◽  
Target Strength

scholarly journals The analysis of echotrace obtained by a split-beam echosounder to observe the tilt-angle dependence of fish target strength in situ

2009 ◽  
Vol 67 (2) ◽  
pp. 215-230 ◽  
Author(s):  
Masahiko Furusawa ◽  
Kazuo Amakasu
Keyword(s):  
Theoretical Model ◽  
Tilt Angle ◽  
Three Dimensional ◽  
Prolate Spheroid ◽  
Target Strength ◽  
Accurate Information ◽  
Careful Selection ◽  
Angle Dependence ◽  
Selection Of

Abstract Furusawa, M., and Amakusu, K. 2010. The analysis of echotrace obtained by a split-beam echosounder to observe the tilt-angle dependence of fish target strength in situ. – ICES Journal of Marine Science, 67: 215–230. A method of echotrace analysis (ETA), proposed by Furusawa and Miyanohana in 1988 utilizes successive echodata from an individual fish to obtain the target-strength (TS) pattern as a function of fish tilt angle and behaviour. The method can be applied to data from an echosounder with any beam configuration, single-, dual-, and split-beam. However, the method has not been applied rigorously to split-beam sounder data, which provide most comprehensive and accurate information. The aim of this work is to establish an accurate and practical ETA method for split-beam echosounder data. Although the basic theory had already been developed, some theoretical and practical enhancement was needed; smoothing of an echotrack by linear and quadratic regressions, correction for transducer motion, and comparison of an observed TS pattern with a prolate-spheroid theoretical model. The analysis starts from careful selection of a single echotrace on an echogram and ends with a composite display of results including a three-dimensional fish track and a TS pattern as a function of the tilt angle of the fish. The method was applied to typical echotrace examples, and utility and practicality were confirmed. A means of increasing the number of applicable echotraces is discussed.

scholarly journals Acoustic target strength (TS) of argentine anchovy (Engraulis anchoita): the nighttime scattering layer

2016 ◽  
Vol 74 (5) ◽  
pp. 1408-1420 ◽  
Author(s):  
Adrián Madirolas ◽  
Federico A. Membiela ◽  
Juan D. Gonzalez ◽  
Ariel G. Cabreira ◽  
Matías dell’Erba ◽  
...  
Keyword(s):  
Tilt Angle ◽  
Regression Line ◽  
Constant Term ◽  
Least Square ◽  
Target Strength ◽  
Data Series ◽  
Angle Distribution ◽  
Scattering Layer ◽  
Depth Dependence

Engraulis anchoita is a physostomous fish with a dual chambered swimbladder (sb). In situ target strength (TS) measurements on this species are only possible at night, when anchovies disperse forming a scattering layer near the sea surface. A survey data series comprising more than 50000 single target detections, recorded from 1995 to 2008, was analyzed in order to study the species specific TS at 38 kHz. A TS vs. fish total length (L) equation was obtained from the in situ measurements (TS = 31.9 log L – 82.4 dB; r2= 0.78). When the slope of the regression line was forced to 20 into the TS equation, the resulting value for the constant term (b20) was −68.6 dB. In any case, these results indicate an average difference of +3 dB (higher TS values) when compared with the general model suggested for clupeoid fish. The TS measurements obtained inside the nighttime sound scattering layer exhibited a negative trend with depth. An empirical depth dependence term for the anchovy TS equation was obtained through a three parameter least square fitting of the data [TS = 31.3 log L – 79.6 dB – 4.74 log (1 + z/10); r2 = 0.74]. Anatomical data obtained through high resolution X-Ray Computed Tomography was employed as input for a Prolate Spheroidal Model (PSM). Theoretical TS vs. tilt angle functions were obtained considering the compression of the sb at different depths and under the assumption of different contraction rates. The TS functions were then averaged over different fish tilt angle distributions and used to derive theoretical depth dependence curves of average fish TS. The implications of the adopted sb contraction rate and tilt angle distribution are discussed by comparing the modelled TS(z) curves against the empirical data.

scholarly journals The influence of beam position and swimming direction on fish target strength

2008 ◽  
Vol 65 (2) ◽  
pp. 226-237 ◽  
Author(s):  
M. J. Henderson ◽  
J. K. Horne ◽  
R. H. Towler
Keyword(s):  
Tilt Angle ◽  
Target Strength ◽  
Major Influence ◽  
Angle Distribution ◽  
Beam Position ◽  
Swimming Direction ◽  
Acoustic Transducer ◽  
Accurate Definition ◽  
Single Target

Abstract Henderson, M. J., Horne, J. K., and Towler, R. H. 2007. The influence of beam position and swimming direction on fish target strength. – ICES Journal of Marine Science, 65: 226–237. Fish orientation is consistently identified as a major influence on fish target strength (TS). Generally, orientation is defined as the tilt angle of the fish with respect to the acoustic transducer, whereas a more accurate definition includes tilt, roll, and yaw. Thus far, the influences of roll and yaw on fish TS have only been examined cursorily. We used in situ single-target data to create fish tracks, to estimate fish tilt and yaw, and correlated these estimates with TS. The results show that tilt, yaw, and beam position have a significant influence on fish TS. To investigate further how yaw and beam position affect TS, we calculated the expected backscatter from each fish within simulated fish aggregations using a backscatter model. The TS of individual fish at 38 and 120 kHz varied by as much as 11 and 19 dB with changes in yaw and beam position. Altering the fish’s tilt, yaw, and beam position resulted in TS differences of 14 and 26 dB at 38 and 120 kHz, respectively. Orientation had a minimal influence on an aggregation’s average TS if the aggregation had a variable tilt-angle distribution and was dispersed throughout the acoustic beam.

A High Angle, Double Tilting Cold Stage for the AEI EM7

1974 ◽  
Vol 32 ◽  
pp. 450-451
Author(s):  
P.R. Swann ◽  
A.E. Lloyd
Keyword(s):  
Habit Plane ◽  
Temperature Control ◽  
Tilt Angle ◽  
Cooling System ◽  
Thermal Drift ◽  
High Angle ◽  
Cold Stage ◽  
High Degree ◽  
Better Than

Figure 1 shows the design of a specimen stage used for the in situ observation of phase transformations in the temperature range between ambient and −160°C. The design has the following features a high degree of specimen stability during tilting linear tilt actuation about two orthogonal axes for accurate control of tilt angle read-out high angle tilt range for stereo work and habit plane determination simple, robust construction temperature control of better than ±0.5°C minimum thermal drift and transmission of vibration from the cooling system.

In Situ Measurement of Soil Heat Flux with the Gradient Method

2003 ◽  
Vol 2 (4) ◽  
pp. 589
Author(s):  
Douglas R. Cobos ◽  
John M. Baker
Keyword(s):  
Heat Flux ◽  
Gradient Method ◽  
Soil Heat Flux ◽  
In Situ Measurement
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