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Science 27 March 2009:
Vol. 323. no. 5922, pp. 1734 - 1737
DOI: 10.1126/science.1169441
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Reports

Critical Population Density Triggers Rapid Formation of Vast Oceanic Fish Shoals

Nicholas C. Makris,1* Purnima Ratilal,2 Srinivasan Jagannathan,1 Zheng Gong,2 Mark Andrews,2 Ioannis Bertsatos,1 Olav Rune Godø,3 Redwood W. Nero,4 J. Michael Jech5

Similarities in the behavior of diverse animal species that form large groups have motivated attempts to establish general principles governing animal group behavior. It has been difficult, however, to make quantitative measurements of the temporal and spatial behavior of extensive animal groups in the wild, such as bird flocks, fish shoals, and locust swarms. By quantifying the formation processes of vast oceanic fish shoals during spawning, we show that (i) a rapid transition from disordered to highly synchronized behavior occurs as population density reaches a critical value; (ii) organized group migration occurs after this transition; and (iii) small sets of leaders significantly influence the actions of much larger groups. Each of these findings confirms general theoretical predictions believed to apply in nature irrespective of animal species.

1 Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA.
2 Northeastern University, 360 Huntington Avenue, Boston, MA 02115, USA.
3 Institute of Marine Research, Post Office Box 1870, Nordnes, N-5817 Bergen, Norway.
4 Southeast Fisheries Science Center, 3209 Frederic Street, Pascagoula, MS 39568, USA.
5 Northeast Fisheries Science Center, 166 Water Street, Woods Hole, MA 02543, USA.

* To whom correspondence should be addressed. E-mail: makris{at}mit.edu

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Science. ISSN 0036-8075 (print), 1095-9203 (online)