HOME AGAIN

Every spring, salt-water fishermen await the return of certain species of fish to a particular area to spawn.  In Delaware Bay, its the weakfish.  Do they return to the waters in which they were born?  Contrary to common belief, the evidence is mounting that this species has a strong homing instinct.

Following the fish over their lifetimes isn't too easy a thing to do.  Some fish don't display discernible genetic differences and  their young can't be tagged.

However, in the weakfish, scientists are using the earbones , which contain periodic growth rings much as does a tree.  These are called otoliths.  As the otolith grows it incorporates calcium carbonate and a chemical signature of the surrounding water.

The otolith "acts like a flight recorder , encoding time-specific information about the waters through which the fish passes, from birth to death," says Robert Warner, a fisheries biologist, speaking of the work done by Simon Thorrold of Woods Hole Oceanographic Institute.

01/08/04 19:19