Scalloped Hammerhead Shark

Photo: Etienne Guitton · CC BY-NC

Hammerheads aggregate around the deeper flanks of Prony during the cool dry season from May to October, circling at 30 to 45 metres in loose schools that occasionally rise to inspect divers at the summit. The thermocline at Prony drops water temperature by as much as 4 degrees Celsius between the surface and 40 metres, and the hammerheads appear to spend time on either side of this layer, suggesting thermal regulation behaviour. Schools of 10 to 40 individuals have been recorded, representing a genuine aggregation rather than isolated transient passes.