Multifrequency backscattering properties of Atlantic herring (Clupea harengus) and Norway pout (Trisopterus esmarkii)

Sascha M. M. Fassler, Rita Santos, Norma Garcia-Nunez, Paul George Fernandes

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

The multifrequency backscattering characteristics of echotraces of Atlantic herring (Clupea harengus) and Norway pout (Trisopterus esmarkii) are described. These fish cohabit similar areas of the North Sea in summer and echotraces of their schools are difficult to distinguish. Mean volume backscattering strengths at 18, 38, 120, and 200 kHz were taken from the International North Sea Herring Acoustic Surveys along with coincident pelagic trawl samples. The results indicate that echotraces of these fish species cannot be distinguished on the basis of differences in backscattering at discrete frequencies typically used in fish surveys and on fishing vessels. However, some discrimination between herring size-classes was evident. The empirical data for herring were then compared with a backscattering model for herring combining fish flesh, the swimbladder, and the effect of increased pressure at depth. Both the empirical data and model data indicate that, compared with large herring, progressively smaller herring generally have higher backscattering at the lowest frequency (18 kHz), although variability was high. According to the model, this frequency-specific signature is due to the progressively more significant contribution made by the fish body compared with the swimbladder, as the latter diminishes owing to an increase in ambient pressure in deeper water.

Original languageEnglish
Pages (from-to)362-374
Number of pages13
JournalCanadian Journal of Fisheries and Aquatic Sciences
Volume64
Issue number2
DOIs
Publication statusPublished - Feb 2007

Keywords

  • target-strength
  • species identification
  • swimbladder compression
  • acoustic scattering
  • fisheries acoustics
  • pelagic fish
  • frequency
  • plankton
  • schools
  • models

Cite this

Multifrequency backscattering properties of Atlantic herring (Clupea harengus) and Norway pout (Trisopterus esmarkii). / Fassler, Sascha M. M.; Santos, Rita; Garcia-Nunez, Norma; Fernandes, Paul George.

In: Canadian Journal of Fisheries and Aquatic Sciences, Vol. 64, No. 2, 02.2007, p. 362-374.

Research output: Contribution to journalArticle

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