Tracking scalloped hammerhead sharks for conservation

Lonely located in the eastern Pacific lies the basalt Island Malpelo. It rises from 4000 meters water depth off the coast of Colombia. There are not many visitors who would be interested in this island. But for marine biologists it is worthwhile to undertake an expedition here. Because this is the home of scalloped hammerhead sharks. Scalloped hammerhead sharks are also at risk in regions where the hammerheads are not hunted themselves because they often get caught in fishing nets. That is why it is important to learn more about their whereabouts and hikes.

With the help of harpoons, scientists want to equip the sharks with transmitters. The signals emitted by the transmitters are received by receivers which are anchored around the island on the ocean bed. It is an expensive technology, nothing should go wrong. The researchers are careful. Each fixture is tested meticulously. The underwater conditions are rough; strong currents and waves could tear off the receiver. While a buoy stabilizes the transmitter upright at the proper depth, a heavy plate provides for grip on the seabed. Divers position the receiver at the selected place. For marine biologists, this technique is the only way to monitor the underwater life around the clock because, at least at night, there are no human beings diving here.

Marine scientists must also be experienced divers. Every move has to be perfectly executed. Under water there no chance to speak, therefore all questions have to be discussed on board. The hardest part starts now. The sharks have to be fitted with the transmitters. This work is undertaken by specialists, apnea divers, who can stay underwater long and deep without air tanks. Compared with scuba divers the free divers have a particular advantage, which the biologists want to take advantage of in their work. They are silent. No loud bubbly and breathing noise scares the animal, additionally there are no clouds of bubbles which obstruct the view. First, the animals must be found. The diver has to position himself behind the sharks to get to a good aim.

The first transmitter is fixed. The next one is handed. Free divers can wait patiently until a hammerhead shark approaches. The better the shot finds its target, the longer the transmitter will be fixed. A perfect result, it hangs prominently on the back of the shark. Worldwide there are only a few specialists who can complete this job successfully. The marine biologists are very content. Now the moment of truth will show. Will the underwater signals be received by the biologists? The scientists steer away the boat to test the range. They let down an antenna from the boat to look for signals. Indeed, the data is clearly indicated on the mobile receiver. Hopefully the transmitter remains intact for a long time. If enough data is collected, they will be able to set up effective protection zones for the sharks.