Air Date: Week of April 29, 2005

An audio postcard from producer Allan Coukell of the sounds of a reef, and the way fish use sound to find their way around.

Transcript

GELLERMAN: We've all seen pictures of an underwater coral reef, but do we know what it sounds like? Fish do and as producer Allan Coukell discovered, some baby fish use the sound to find their way home.

COUKELL: Nick Tolimieri is a biologist at the Northwest Fisheries Science Center in Seattle. Standing by the bay where he did his post-doc research, he explains how he recorded and played back the sounds of an underwater reef.

TOLIMIERI: So, what we did was to go at night out and put a hydrophone in the water by a reef and record the noise that comes off a reef. And a reef can be incredibly noisy.

[REEF SNAP CRACKLE POP SOUND]

TOLIMIERI: This is just sound recorded off of a reef, about an hour or two after sunset, and the noise is mostly sea urchins and snapping shrimp–a lot of the pops are probably the snapping shrimp. And both of these things tend to come out at night and it's actually been called the evening chorus.

COUKELL: A lot of marine organisms, especially fish, spend their adult lives on a reef, but disperse to the open ocean as babies. Later these larval fish somehow find their way back to the reef.

TOLIMIERI: These little fish larvae that are only a centimeter or two centimeters long – they can actually locate a reef from as far away as a kilometer or two. They seem to know where they are and they'll avoid reefs during day, probably because they don't want to be eaten by the bigger fish.

COUKELL: To find out how the fish find their way back, Tolimieri went fishing at night, playing tapes of underwater reef sound and catching the fish larvae in an illuminated underwater net, called a light trap.

TOLIMIERI: And we put some light traps out with sound equipment and some light traps out without sound equipment and see how many are coming to the ones with sound and the ones without sound. And for the species we've done so far, we've gotten about five times as many reef fish in the ones with sound as we have in the ones without sound.

[SWISHING AND DRIPPING SOUNDS OF FISH LARVAE]

COUKELL: Not only can fish larvae hear extremely well, but they are also good swimmers. Scientists have found that some species, following the siren's call of the reef, can swim up 300 miles without eating or stopping. For Living on Earth, I'm Allan Coukell.

[MUSIC: Teisco Del Ray "Missterri Meat" Plays Music for Lovers (Upstart Sounds) 1996]