Hostname: page-component-cd9895bd7-gxg78 Total loading time: 0 Render date: 2024-12-27T10:55:44.089Z Has data issue: false hasContentIssue false
  • English
  • Français

Avoidance behaviour in cod (Gadus morhua) to a bottom-trawling vessel

Published online by Cambridge University Press:  15 July 2003

Nils Olav Handegard ,
Kathrine Michalsen  and
Dag Tjøstheim
Nils Olav Handegard*
Affiliation:
Institute of Marine Research, P.O. Box 1870 Nordnes, 5817 Bergen, Norway Department of Mathematics, University of Bergen, P.O. Box 7800, 5020 Bergen, Norway
Kathrine Michalsen
Affiliation:
Institute of Marine Research, P.O. Box 1870 Nordnes, 5817 Bergen, Norway
Dag Tjøstheim
Affiliation:
Department of Mathematics, University of Bergen, P.O. Box 7800, 5020 Bergen, Norway
*
nilsolav@imr.no
Get access

Abstract

The reaction of fish induced by a trawling vessel was measured using the Bergen Acoustic Buoy. It is a free-floating buoy with a split beam echo sounder system. Individual fish trajectories were obtained by target tracking methods, and average swimming velocities as a function of depth and time before and after passage of the vessel was calculated. A measure for the change in behaviour was applied, showing a significant response during and after propeller passage. The change in horizontal displacement speed is significant at all depths, while the change in vertical displacement velocity is significant at all but one layer of depth. The horizontal reaction seems to occur a bit later than the diving reaction. After the main response, a slightly higher mean horizontal displacement speed was observed for the deepest layers. This indicates a change in the fish state after being exposed to the vessel/gear.

Keywords

Cod avoidanceTarget trackingAbundance estimatesAcoustic buoyBottom trawl
Type
Research Article
Information
Aquatic Living Resources , Volume 16 , Issue 3: Acoustics in Fisheries and Aquatic Ecology. Part 2 , July 2003 , pp. 265 - 270
Copyright
© Elsevier, IRD, Inra, Ifremer, Cemagref, 2003

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)