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American Association for the Advancement of Science

What triggers giant fish schools?

Two may be company and three a crowd, but for herring, a few more makes things really exciting.

Using new imaging technology, researchers now show how when herring numbers reach a certain density, they form massive schools, or "shoals," that can assemble in minutes and cover tens of kilometers.

The similarities in the behavior of large groups of animals, such as bird flocks, fish shoals, and locust swarms, has scientists interested in learning about how and why animals form highly organized crowds.

Collecting information about these groups has been difficult, though. Fish, for example, are spread over such wide areas in the darkness of the ocean that they have been difficult to locate, count and study.

Nicholas Makris of the Massachusetts Institute of Technology and colleagues used a method called Ocean Acoustic Waveguide Remote Sensing to track Atlantic herring populations over tens of thousands of square kilometers across on Georges Bank, off the New England coast, in real-time.

They found that the group behavior changes quickly from disordered to highly synchronized once the crowding reaches a certain density. After that point, the group begins to migrate in an organized way.


This research appears in the 27 March issue of the journal Science.