Why do animals migrate?

For the first time, engineers at MIT observed the beginning of a centralized migration event involving hundreds of millions of animals.

In an article by an engineering group published in the March 27 issue of Science, research conducted using a new modeling technique that provides information needed for the conservation of marine ecosystems and colonies Large ocean fish settled.

The study also confirmed the hypotheses of the behavior of large groups of animals in general, from birds to grasshoppers. To date these studies are only predicted through theoretical research, computer simulations or experiments.

For example, the team found that once a fish population reaches a certain population density, it will cause a chain reaction that leads to the anabolic activity of millions of individuals in a large area. This phenomenon is quite similar to the wave of people moving in the stadium. Nicholas C. Makris - research director and professor of ocean and mechanical engineering - said: 'Compared to what we know, this is the first time this behavior has been identified in nature in the birth system. wide. The gathering of migratory fish species can expand up to 40km, approximately 25 miles. "

Makris' colleagues in the study included Dr. Purnima Ratilal professor at Northeastern University, J. Michael Jech of Northeastern Fish Science Center, and Olav Rune Godoe of the Norwegian Marine Biology Research Institute. Other partners are from MIT and the Southeastern Fish Research Center.

Watching offshore

The team focused on Atlantic herring herds near Boston during the spawning season when it was autumn. They found the formation and movement of large fishes every night, swimming among shallow waters where they lay eggs under the protection of darkness. When morning came, they returned to deeper and scattered waters. The study was carried out by OAWRS remote control device. In 2006, Makris and colleagues published a Science article to introduce the OAWRS device. They invented it and made first observations with it.

The diagram showing the image system is used to study the assemblage of fish. (Photo: Makris Lab, MIT; Ratilal Lab, NU)

OAWRS allows the team to get images in an area 100 kilometers (62 miles) in diameter every 75 seconds . This is a big step forward compared to conventional techniques such as the fish finder that Makris compares to 'watching 1 pixel on the screen' , while new technology allows 'see the whole set'. movie'.

Both OAWRS and conventional methods rely on sound to locate objects thanks to reverberating sounds. With conventional techniques, the research boat must emit high-frequency sounds into the sea. In contrast, the new system using lower frequency sounds can travel much longer distances while still providing useful information.

Towards conservation

Makris sees the potential in using OAWRS to control, thereby preserving, fish populations. Large fish colonies that live in the ocean provide important connections in the ocean and in the human food chain. But their size makes it difficult to collect information based on common sense.

Ron O'Dor, a scientist from the Marine Life Investigation Agency (CoML), commented: 'OAWRS allows us to gather information such as geographic distribution, abundance and behavior. fish stocks, thereby increasing our understanding of the factors that make up healthy fish populations. This will help policy makers control and improve fish conservation '. CoML is an international coordinating agency in a 10-year program aimed at evaluating and explaining the diversity, distribution and abundance of marine life. The program aims to deliver the first results in 2010.

Can OAWRS be exploited to find and catch more fish than to preserve them? Makris believes that this is impossible. He said it could not be used in illegal fishing. 'Thieves do not like to work during the day or when lighting the lights. OAWRS basically needs to turn on the light when under the variable so people can see what's happening there. ' He also emphasized that permission from governments is necessary for this device to be used in territorial waters or in international waters.

The study was funded by the National Oceanographic Coordination Program, the Naval Research Office and the Alfred P. Sloan Foundation. This is also a part of the marine life investigation project.