Journal Article

Improving acoustic estimates of krill: experience from repeat sampling of northern krill (<i>Meganyctiphanes norvegica</i>) in Gullmarsfjord, Sweden

Inigo Everson, Geraint A. Tarling and Bo Bergström

in ICES Journal of Marine Science

Published on behalf of ICES/CIEM

Volume 64, issue 1, pages 39-48
Published in print January 2007 | ISSN: 1054-3139
Published online November 2006 | e-ISSN: 1095-9289 | DOI: http://dx.doi.org/10.1093/icesjms/fsl010
Improving acoustic estimates of krill: experience from repeat sampling of northern krill (Meganyctiphanes norvegica) in Gullmarsfjord, Sweden

More Like This

Show all results sharing these subjects:

  • Environmental Science
  • Marine and Estuarine Biology

GO

Show Summary Details

Preview

Everson, I., Tarling, G. A., and Bergström, B. 2007. Improving acoustic estimates of krill: experience from repeat sampling of northern krill (Meganyctiphanes norvegica) in Gullmarsfjord, Sweden – ICES Journal of Marine Research, 64, 39–48.

A series of eight replicated acoustic surveys, four by day and four by night, was undertaken in Gullmarsfjord on the Swedish west coast during two 24-h periods on 8 and 10 September 2003, using a calibrated echosounder operating at 120 and 38 kHz. The difference in signal strength (ΔSv) was used to distinguish northern krill (Meganyctiphanes norvegica) from other acoustic scatterers. The approach is concluded to be very effective, but it can be improved greatly by applying the following series of simple extensions to current protocols: first, set a very low threshold on both frequencies to minimize sampling bias; second, undertake tests to confirm that the data extracted from each acoustic frequency apply to the same scatterers; third, ensure that the range of ΔSv is not greater than the TSrange at either frequency; and finally, when abundance estimation is the primary aim, arrange for sampling at the time of day and using the acoustic frequency that together provide the least variance.

Keywords: acoustic surveys; dB difference; Meganyctiphanes norvegica; northern krill

Journal Article.  5552 words.  Illustrated.

Subjects: Environmental Science ; Marine and Estuarine Biology

Full text: subscription required

How to subscribe Recommend to my Librarian

Users without a subscription are not able to see the full content. Please, subscribe or login to access all content.