Modelling three-dimensional directivity of sound scattering by Antarctic krill: progress towards biomass estimation using multibeam sonar

George R. Cutter, Josiah S. Renfree, Martin J. Cox, Andrew Stuart Brierley, David A. Demer

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)

Abstract

Target strength (TS) estimation is a principal source of uncertainty in acoustic surveys of Antarctic krill (Euphausia superba). Although TS is strongly dependent on krill orientation, there is a paucity of information in this regard. This paper considers the potential for narrow-bandwidth, multibeam-echosounder (MBE) data to be used for estimating the orientations of krill beneath survey vessels. First, software was developed to predict MBE measurements of the directivity patterns of acoustic scattering from individual or aggregated krill in any orientation. Based on the distorted-wave, Born approximation model (DWBA), scattering intensities are predicted vs. MBE angles for specified distributions of krill orientations (pitch, roll, and yaw angles) and swarm densities. Results indicate that certain distributions of orientations, perhaps indicative of particular behaviour, should be apparent from the sonar data. The model results are compared with measurements on krill made using a 200-kHz MBE deployed from a small craft off Cape Shirreff, Livingston Island, Antarctica, in summer 2006. The stochastic DWBA model is then invoked to explain disparities between the model predictions and MBE measurements.

Original languageEnglish
Pages (from-to)1245-1251
Number of pages7
JournalICES Journal of Marine Science
Volume66
Issue number6
DOIs
Publication statusPublished - Jul 2009

Keywords

  • Antarctic krill
  • directivity
  • incidence angle
  • multibeam sonar
  • orientation
  • target strength
  • TARGET STRENGTH MEASUREMENTS
  • WAVE BORN APPROXIMATION
  • IMPROVED PARAMETERIZATION
  • ACOUSTIC SCATTERING
  • BROAD-BANDWIDTH
  • FISH SCHOOLS
  • 120 KHZ
  • ORIENTATION
  • BEHAVIOR
  • AVOIDANCE

Fingerprint

Dive into the research topics of 'Modelling three-dimensional directivity of sound scattering by Antarctic krill: progress towards biomass estimation using multibeam sonar'. Together they form a unique fingerprint.

Cite this