Coral reefs may all smell the same to humans. But to some fish, reefs' smells have distinct qualities — even when they're several hundred miles away.
A new study in the Proceedings of the National Academy of Sciences argues that some reef fish use smelly ocean currents the way New Yorkers use their subway lines — as the quickest way home.
Scientists have long known that salmon smell their way back to their birth streams, but until now, nobody knew that reef fish did it, too.
In one experiment, the team put cardinal fish larvae into the aquatic equivalent of a subway station. It allowed the fish to chose between two water trains, one of which was from their home reef. Almost every time, the larvae jumped into the stream that smelled like home, even when the researchers tried to trick them by switching the odor around.
But the study has attracted critics. They say one big problem is that the chemcial compounds that might be creating the odors are never identified.
But evoluntionary biologist Richard Zimmer of the University of California at Los Angeles says the study raises some intriguing possibilties. For instance, if these smelly currents turn out to exist, they could be used to lure fish back to reefs that are facing all kinds of problems.
"There is tremendous interest in knowing what processes get fish to a particular reef," Zimmer says, "so that, ultimately, reefs can be more effectively managed."