MEPS - Vol. 299 - Feature article

Swarms of krill were patrolled by large piscivorous fish. The piscivores preyed on planktivores attracted by the swarms, at the same time providing protection for the krill. Illustration: Hege Vestheim

Stein Kaartvedt, Anders Røstad, Øyvind Fiksen, Webjørn Melle, Thomas Torgersen, Mari Tiseth Breien, Thor A. Klevjer

 

Piscivorous fish patrol krill swarms

 

Many species of krill (pelagic crustaceans) form swarms of great size, and thereby constitute a key component of offshore ecosystems. Kaartvedt, Røstad, Fiksen, Melle, Torgersen, Breien & Klevjer observed swarms of northern krill Meganyctiphanes norvegica being followed (patrolled) by large piscivorous fishes. They conclude that the swarms provide a feeding ground for large piscivores, which hunt for the smaller planktivorous fishes that prey upon the krill. In this way, the large fishes provide protection for the krill, according to the rule that 'the enemy of my enemy is my friend'. Thus, social aggregations of krill are 'hot spots' of predator–prey interactions at several trophic levels.

 

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