Migration behaviour of herring along the cold front in the Norwegian Sea in April 1997

The behaviour of Norwegian spring spawning herring when migrating to the feeding areas in the Norwegian Sea in April was mapped by an acoustic survey in 1997. The distribution of herring was recorded by conventional echo integration, and the swimming behaviour of selected herring schools was recorded by a high-resolution sonar. Individual schools were tracked for up to o ne ho ur. The herring were recorded in an area between 66° and 68° north, 2° east to 3° 30' west. The western part of the area was influenced by the southbound, cold East Icelandic current which induced a termal front within the area. Schools far east of the front had a western migration direction, while schools closer to the front had a southern migration direction. The migration behaviour of the herring schools seemed to be influenced by the temperature distribution in the front. The herring were recorded in large dense schools at 200 - 400 m during daytime. At night the schools rose to surface and scattered or remained as distinct schools