What makes reef noise?
New Zealand reefs are noisy places. Why and what is making all that noise? Postdoctoral fellow Dr Craig Radford of the Leigh Marine Laboratory talks about some of the noisy species found on New Zealand reefs.
Point of interest: In this video clip, you’ll hear some of the unique noises John Dory and gurnard fish make. Listen carefully!
Transcript
DR CRAIG RADFORD If you think back to the 50s when Jacques Cousteau was first diving and he called it the silent world. Well, it’s not actually silent. It’s really noisy, because the animals themselves make a lot of noise and also by the waves and wind acting on the surface.
So we set up an experiment where we wanted to quantify how underwater sound fluctuates with time of day. So if you think about time of day, you divide it up into the four periods – you’ve got dawn, dusk, actual day itself and night – and we found that dusk is the loudest time of the day, and that’s mostly due to the animals being more active during this period.
The main animal that we found here in New Zealand that produces reef sound is the sea urchin or the kina. This spiky little critter produces a lot of noise via its feeding activity. We know that an urchin, their greatest activity period is during dusk when there is a lot less predators. At dusk, we know the urchins are active, and we know that they produce sound in a certain frequency, and we can see that by analysing this sound.
Snapping shrimp are the second dominant reef sound producer here in New Zealand. They’ve got one enlarged claw, compared to what they other one is like, and they produce sound by the claw rapidly closing, and that forms a water jet, and when that water jet collapses under the pressure of the surrounding water, it makes a snap, and that is how they make sound.
And there’s other sound producers such as fish. Gurnard are dominant, and they have a variety of sounds they produce – grunts, growls and groans – and also we’ve got John Dory, and they make a… they kind of bark like a dog.
Acknowledgement: Brady Doak, Leigh Marine Lab Jacqueline Corkery, CBC Canadian Broadcasting Corporation NZ Fisheries
