Pretty patterns but a simple strategy: predator-prey interactions between juvenile herring andAtlantic puffins observed with multibeam sonar

Predator-prey interactions between Atlantic puffins (Fratercula arctica) and newly metamorphosed herring(Clupea harengus) were studied in the Lofoten-Rost area in northern Norway using a high-resolution multibeam sonarsystem. Attacks from diving puffins and predatory fish induced massive predator-response patterns at the school level,including bend, vacuole, hourglass, pseudopodium, herd, and split. All patterns have previously been observed, usingthe same sonar, in schools of adult herring attacked by groups of killer whales. Tight ball, the prevailing responsepattern in adult fish under predation, was not observed, but a new pattern, intraschool density propagation, was foundand interpreted as an analogue to tight-ball formations moving rapidly within the school. The observed patterns persistedmuch longer than in schools of adult herring attacked by killer whales, reflecting the different hunting strategies.Traditionally, the repertoire of predator responses observed in schooling fish has been interpreted as a range of cooperativetactics to trick predators, but this has recently been challenged by authors who suggested that fish that behavethe same way produce different patterns at group level simply by maintaining a minimum approach distance to predatorsand hiding behind conspecifics (the ‘selfish herd’), and that the particular combination of group size and numberand behaviour of predators, rather than different individual tactics, determines the outcome at group level. Our findingssupport the latter hypothesis.

Bjorn Erik Axelsen, Tycho Anker-Nilssen, Petter Fossum, Cecilie Kvamme, and Leif Nottestad, Can. J. Zool. 79: 1586-1596 (2001)