Killer whales (Orcinus orca L.) and saithe (Pollachius virens L.) trap herring (Clupea harengus L.) in shallow water by taking advantage of steep bottom topography

Abstract

Whales and fish use a wide range of hunting tactics in order to catch their prey. Predatorprey interactions have been seen during the massive wintering of herring (Clupea harengus) in steep bottomed topography in Lofoten, northwestern Norway. We applied hydro-acoustics to document how killer whales (Orcinus orca) and Atlantic saithe (Pollachius virens) herd and trap herring in shallow waters before attacking their prey. A group of eight killer whales and a shoal consisting of hundreds of saithe concentrated their attack on the side of the herring schools that faced away from the shallow area. They thus effectively herded the herring towards the shallower water. The predators then surrounded the schools, preventing the herring from escaping to deeper, darker and safer water. Some predators attacked herring by penetrating the school, while others continued surrounding the school. These are the first, well-documented hydro-acoustic observations of this hunting tactic. Further research will reveal if this hunting tactic is common and widespread among other species of marine mammals and fish preying on fish schools in coastal waters.