Ocean News

What makes great hammerheads so great?

27th February 2009

For me, there are few sharks out there that evoke the same sense of awe and admiration as Sphyrna mokarran; the great hammerhead shark. I’ve only seen one in all my years of diving, and that was just a fleeting glimpse; by the time my mind had registered that it was a great hammerhead, it had already disappeared. This brief sighting was on ourexpedition to Aldabra in 2008

There are many species of hammerhead shark; the ones you may be most familiar with are scalloped hammerheads. These are seen in large groups in many parts of the world, from the Red Sea to Costa Rica. The great hammerhead is an altogether different and more imposing animal.

Generally solitary, and growing much larger than their scalloped headed cousins, the great hammerhead can grow up to 6 meters in length, that’s as big as great white sharks. There are even (unsubstantiated, yet very reliable) reports of great hammerheads in the Indian ocean, growing to lengths far far exceeding that of  even the largest great whites ever caught. Scary stuff you say?  Well, not really.  Despite being listed as ‘potentially aggressive’ there’s not a single confirmed report of a great hammerhead attacking a human. I suspect these sharks are going to be hard work, difficult to get close to, and will be somewhat camera-shy.

So why go and try and film them in the first place?

Well, since the mid 80’s, catch rates for hammerhead sharks (all species of hammerheads not just greats) are down 89% in the northwest Atlantic. According to traders of shark fins, hammerhead fins are some of the most valuable on the market; unprocessed they are worth as much as $135 per kg. This means that hammerheads are in big demand, and so are in big trouble. Like many species of shark their populations teeter on the verge of complete collapse. The lifestyles of all sharks makes them vulnerable to extinction; late maturation, small litter size, and high commercial value. Great hammerheads only reproduce every two years, making them even more vulnerable.

One of the core goals of SOSF is education and awareness through film and photography, so Tom Peschak and myself will be spending a week focusing on collecting high quality video footage and still images of this magnificent shark, to help raise awareness of the need to conserve them.

I’ll keep you posted as to how we get on.