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Adult reef fish stick close to home over most of their lifetime. Some fish breed by freely shedding eggs and sperm into the water column which meet by chance, begin to develop, float away then, at a certain stage of development, actively seek out a place to settle down. Marine biologists have long thought the gene pool on any given reef was well mixed across reef habitats.

In recent years this view has come under question. Reef fish communities appear to be closed systems, that is, large numbers of fish of the same species have similar gene patterns, suggesting fish larvae make their way back to the reef from which they originated. This has been substantiated by both genetic studies and larval release experiments where the larvae seem to head for home.

These finding have significance in managing reefs. When a protected area is set up, the adult fish grow in size and numbers, producing more eggs. If those juveniles stay close to home, local communities have more incentive to create a protected reserve because it will benefit local fisheries. Limited larval movement also suggests each area will need a reserve to count on its own supply.

Not all marine biologists agree with these findings. Some think scale (the size of the community) and currents dominate what happens on the reef.

Science v 290 p 1282-3

01/08/04 19:12