Sharks battle for survival

March 19, 2008

Henri du Plessis March 14 2008 at 12:24PM

It may seem a rather small victory, requiring huge effort, to return one captive shark to the ocean successfully while its kin are being hunted to extinction in that same ocean.The feared and often hated creature, often the villain in film, does not easily generate warm and fuzzy feelings of sympathy and understanding among humans who are far more likely to embrace "cute", but equally dangerous, polar bears.But, as powerful a hunter and killer as the shark may seem to be, it is extremely vulnerable to one other predator people.And a great part of this vulnerability has to do with the lack of knowledge people have of the role the shark plays in the environment.Now, the battle of the survival of the shark is being fought on two fronts through gaining greater knowledge of their ways and through communication.Mike Meyer of the department of environmental affairs and tourism's marine and coastal management division and Dr Malcolm Smale of Bayworld in Port Elizabeth are heavily engaged in the former. Leslie Rochat, founder of the AfriOceans Conservation Alliance, is focused on the latter.The trio have worked extensively with the Two Oceans Aquarium for a number of years, focusing on the study, tagging and release of ragged tooth sharks. The programme, initiated by Rochat, has seen a good measure of success gathering information about the habits and movements of this particular species four captive and six non-captive individuals have been tagged."The fact that we never knew much about them and that we suddenly had the opportunity to study them, made us jump at it," Meyer said this week, while preparing to release their latest subject, the ragged tooth shark Elle, at Struisbaai.Elle, an inmate of the Two Oceans Aquarium in the V & A Waterfront, had been in captivity since 2005, after being caught by a Struisbaai fisherman."We connect an electronic tag to the shark's dorsal fin in such a way that it actually trails behind the dorsal fin while the shark swims. As a result, it does not restrict the shark's movement," Meyer explained."The tag is set to come off after a fixed period of time, pop up to the surface and transmit a signal to a satellite system that downloads a lot of information about the shark's movements and environment."The R35 000 tag, a microphone-shaped object of about 15cm in length, has a 15cm antenna attached to its upper end and records, every 10 seconds, the depth at which the animal finds itself, the water temperature, the speed at which it moves, the direction in which it moves and other factors.Results from data received by satellite and some downloaded from recovered tags have sometimes been surprising, Smale said.One of the biggest surprises was that the behaviour of a shark that had been in captivity did not differ radically from that of a shark caught, tagged and released at sea. "The captive shark instinctively seemed to immediately launch into typical behaviour and followed known migratory patterns," he said.But, apart from the comparisons, general information that emerged from tags showed the sharks doing unexpected things such as dive suddenly and deeply."Now that we can get the information, we can try to interpret it and develop a picture of the life of a shark," Smale said.Improved knowledge of the shark's habits and behaviour would allow a greater understanding of how they fit into the ecology of the sea and how better to manage and protect them, the two marine biologists said.Another tag, implanted in the shark's belly, is read by seabed base stations placed in certain locations along the coast. When the shark moves past the seabed station, it is read and recorded. This allows scientists to see where which shark had been along their migratory routes.Eight years ago, a ragged tooth shark named Maxine found its way to the aquarium. It had a scar around its neck, later shown to have been an injury sustained in a shark net off the coast of KwaZulu-Natal. Rochat, a former environmental journalist and estate agent, studied the shark's story and her interest in these predators peaked. The result was the founding of her non-profit conservation body, AfriOceans Conservation Alliance."Scientists write very detailed but, unfortunately, boring papers on their studies. I wanted to popularise it, make it available to people all over the world," she explained."Since we started, we have reached about 100 million people around the world with the message that sharks needed to be protected. This is according to the people who measure the reach of articles, hits on websites and so on. "I do documentaries, we have a website, designed awareness and educational campaigns, we have had media coverage and have written books on it. People need to be made aware of the need to protect sharks."

This article was originally published on page 13 of Cape Argus on March 14, 2008