Going home

Although some species of fish provide a modicum of parental care after breeding, many species simply cast eggs and sperm into the water column and leave parenthood to fate. This is true for a preponderance of reef fish.  Where these drifting larval fish spend their childhood is a mystery.  It has long been thought they simply remain “offshore” until they reach a certain size or age and then look around for a suitable reef to settle on  as they mature.  Thus, what fish winds up on what reef seemed to be a matter of chance. 

However, a recent study off St.Croix and the Great Barrier Reef indicates that larval fish find their way back to the reef on which they were born.  By tagging fry, one scientist estimated that 15 to 60 percent of the juveniles found offshore do make it back from whence they originated.  Another group measured metals content of larval fishes ear bones and found most spent their early days close to shore; that is, they never did drift far out to sea. 

These results were unexpected because it has been thought larvae have very little control over where the currents take them. However, one marine biologist speculated that simply by swimming vertically  fish could find friendly currents that would keep  them in proximity to the reef  over which they were born.  How do they find the reef?  Probably by sound speculates one biologist.  A reef is a noisy place.  A sense of smell might play a role as well.

                                                                                            N.Y.Times  July 4, 2000

01/08/04 19:16