Evaluation of the Dual Beam Acoustic Fish Target Strength Measurement Method

Abstract

During surveys to assess fish stocks, the acoustic scattering properties of the fish population are required to obtain stock size measurements. The recently developed dual beam technique of target strength measurement has shown great promise as a method for fish target strength measurement. An improved dual beam target strength measurement system is described, and we report the application to a marine population of walleye pollock (Theragra chalcogramma). In addition, we discuss field calibration using a ping-pong ball as a standard target. Results of target strength measurements of the fish and ping-pong ball are compared with predicted values based on simulation analyses of the technique operating under the noise conditions observed in the field. The agreement between field results and theoretical predictions were quite good. Key words: hydroacoustic, walleye, pollock, dual beam, target strength measurement, fish assessment

Use of Multibeam and Dual-Beam Sonar Systems to Observe Cavitating Flow Produced by Ferryboats: In a Marine Renewable Energy Perspective

“…The resulting effect is a coaxial beam pattern featuring a core beam within a relatively broad beam. The beam pattern can be pre-determined by comparing the two output signals if a single target is detected [34]. This procedure allows the direct measurement of backscattering cross-section by removing the beam pattern.…”

Bay anchovy Anchoa mitchilli production and consumption in mid-Chesapeake Bay based on a bioenergetics model and acoustic measures of fish abundance

“…Acoustic data were adjusted for signal spreading and absorption and then fed through a digital audio processor and tape interface to a digital tape recorder. Echo-squared integration and dual-beam analyses of the acoustic data provided measures of acoustic target strength and fish density (Traynor & Ehrenberg 1979, Burczynski & Dawson 1984, Burczynski & Johnson 1986). Fish densities were measured throughout the water column using narrow depth intervals (0.5 m) and averaged over constant time intervals (10 S, ca 25 m) that were determined on the basis of observed scattering patterns.…”

Evaluation of a Rubber-Compound Diaphragm for Acoustic Fisheries Surveys: Effects on Dual-Beam Signal Intensity and Beam Patterns

“…This is not a substantial effect for accurate measures of total backscattering for echo integration or more importantly for individual echoes, since echoes only within a beam pattern threshold of 3 dB, or approximately one-half the nominal beam width, should be used for calculation of mean target strength with dualbeam system [9]. Table 3 Parameter estimates, 95% confidence intervals (CI), and corrected R 2 values for directivity relations of narrow-and wide-beam patterns measured through a rubber diaphragm at three angles of incidence …”