Sharks’ short shrift in life aquatic

I WENT ‘cage-diving’ with great white sharks off South Africa’s Dyer Island last month. The giant fish are lured to the boat by a smelly concoction of offal and the head of a large tuna, suspended from a line in the water.

Nothing happened for several minutes after entering the cage. Then, suddenly, a shark emerged from the dark depths below. Encountering a 4.5m giant, an arm’s length away, is an exhilarating experience. Other sharks arrived. The cage lurched as one collided with it, giving a vivid sense of how massive these creatures are.

Great whites are in the news just now; a decade-long research project on these wonders of the deep is drawing to a close in New Zealand. Dr Malcolm Francis and colleagues at the National Institute of Water and Atmospheric Research have tried to discover where great whites go and what their habitat needs are. Ninety-five sharks have been tagged in New Zealand waters since 2005. Sensors attached to dorsal fins provided data on migration and local movements. Pop-up acoustic tags gathered information on light levels, temperature and depth.