Traveling Fish

Coral reef fish hatchlings carried away by ocean currents return to their home reefs to spawn 60 percent of the time, says a recent study published in the journal Science.

To make the find, scientists used new, internal tagging technology on reef-dwelling clownfish (pictured above) and vagabond butterflyfish. The researchers tagged fish at the reef surrounding a small island, Kimbe Island, in Papua New Guinea.

“This will help in the rebuilding of threatened fish populations,” said Glenn Almany, co- author of the study.

This is the first time scientists have successfully used a new internal tagging method, which involves injecting radioactive, but harmless, barium into breeding female fish. The radioactive isotopes become incorporated into the ear bones of developing embryos, so when the fish grow up and return the barium can be detected—and open-water survivors counted.

At a time of increasing pressures on coral reef ecosystems, the study provides important information for reef conservationists. “40 percent of the juveniles came from other reefs that are at least ten kilometers (five miles) away,” said Almany, which “shows how marine protected areas can contribute to maintaining fish populations outside no-fishing zones.”

—LiveScience Staff

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Credit: Simon Thorrold/Woods Hole Oceanographic Institution