Young Fish Return to "Home Reefs" to Settle Down

Scott Norris
for National Geographic News
May 4, 2007

After spending weeks adrift in the ocean as tiny larvae, juvenile coral reef fish often return to their "home reef" to settle down, researchers say.

The strong homing behavior shown by reef-dwelling butterflyfish in the waters near Papua New Guinea came as a surprise to scientists, and it may have important implications for the design of marine reserves.

Researchers and fisheries managers have long sought better information on how very young fish disperse in the ocean.

Tracking the fate of tiny larvae has been extremely difficult, since the fish are too small for even the smallest electronic tags.

So a team led by Glenn Almany of Australia's James Cook University used a new method for chemically "tagging" fish while still in the egg stage inside their mothers' bodies.

Later recovery of the tagged juveniles showed that as the fish matured, they returned to their place of birth.

On a very small reef, the team found, more than 60 percent of the young, recently settled fish were offspring of adult fish living in the same location.

"We were shocked to find that so many larvae returned to their parents' reef after 38 days in open waters," Almany said.

The team's report appears in this week's edition of the journal Science.

Parental Involvement

For their study the researchers tracked two fish species with different reproductive strategies.

"Each represents one of the two dominant modes of reproduction found in marine fishes," Almany noted.

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