Team IDs genesis of mass migrations( CAMBRIDGE Mass.--For the first time ...)

CAMBRIDGE, Mass.--For the first time, MIT engineers and colleagues have observed the initiation of a mass gathering and subsequent migration of hundreds of millions of animals in this case, fish.

The work, conducted using a novel imaging technique, "provides information essential to the conservation of marine ecosystems that vast oceanic fish shoals inhabit," the team writes in the March 27 issue of Science.

It also confirms theories about the behavior of large groups of animals in general, from bird flocks to locust swarms. Until now those theories had only been predicted through theoretical investigations, computer simulations and laboratory experiments.

For example, the team found that once a group of fish reaches a critical population density, it triggers a kind of chain reaction resulting in the synchronized movement of millions of individuals over a large area. The phenomenon is akin to a human "wave" moving around a sports stadium.

"As far as we know, this is the first time we've quantified this behavior in nature and over such a huge ecosystem," said Nicholas C. Makris '83, PhD '91, leader of the work and a professor of mechanical and ocean engineering. The resulting shoals of migrating fish can extend some 40 kilometers or approximately 25 miles across the ocean.

Makris' principal collaborators on the work include Purnima Ratilal PhD '02, a professor at Northeastern University, J. Michael Jech of the Northeast Fisheries Science Center, and Olav Rune Godoe of the Institute of Marine Research in Norway. Other collaborators are from MIT, Northeastern and the Southeast Fisheries Science Center.

The researchers focused on Atlantic herring off Georges Bank near Boston during the fall spawning season. They found that the formation and movement of large shoals of the fish constituted a kind of daily evening commute to the shallower waters of the bank where they spawn
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