Recording the migration behaviour of fish schools by multi-beam sonar during conventional acoustic surveys

• Published in: ICES Journal of Marine Science
• Main Authors: Hafsteinsson, M. T., Misund, O. A.
• Format: Text
• Language: English
• Published: Oxford University Press 1995
• Subjects: Articles; Barents Sea
• Online Access: http://icesjms.oxfordjournals.org/cgi/content/short/52/6/915; https://doi.org/10.1006/jmsc.1995.0088

Recordings of the swimming behaviour and migration of pelagic fish schools were made during three conventional acoustic surveys, two on herring in the North Sea in July 1991 and 1992, and the third on capelin in the Barents Sea in January 1992. The recordings were made using multi-beam sonar (Simrad SR240 and Simrad SA950) connected to external devices for data logging. A method for the graphical presentation of swimming tracks of schools was established for analysis of the swimming behaviour of the schools. On the basis of their swimming tracks, schools were categorised by three predefined criteria: migrating , vessel avoiding or undetermined . About 20% of the herring schools seemed to avoid the survey vessel, while 60–80% of the schools were categorised as migrating . The capelin schools seemed to be migrating on more than 90% of the occasions. During both North Sea surveys, the majority of the herring schools observed were migrating south. The direction of migration of the capelin was northwards. The average swimming speed of the herring schools was in accordance with theoretical considerations and the results of earlier sonar studies conducted under similar conditions in the North Sea. The validity of estimated swimming speeds of capelin was less certain, as the swimming performance of this species is not well known.