04 March 2008

Elle set for release

Two Oceans Aquarium
Divers direct Elle into a clear PVC bag. Photograph by Natasha Townsend.

Another ragged-tooth shark is set for release from the Two Oceans Aquarium in the second week of March. Elle or Elzanne, as she is affectionately referred to by members of staff, will join the shark release hall of fame which includes Maxine, Val and Dee. These ragged-tooth sharks were released from the Aquarium in 2004, 2005 and 2006 respectively as part of the SaveOur Seas Foundation Maxine, Science, Education and Awareness(M-Sea) Programme, an AfriOceans Conservation Alliance (AOCA) initiative, sponsored by the Save Our Seas Foundation.

The shark release team including Michael Farquhar, the Aquarium’s Curator and Lesley Rochat, AOCA’s founder, are looking forward to Elle’s successful release in light of the tragic deaths of Billy and Bella who were set to be released last year. We were deeply saddened by the Billy-Bella tragedy; it was a huge setback for the Programme which had, until then, been so successful and positive, said Rochat.

Elle arrived at the Aquarium in April 2005 together with M.J. These two young female ragged-tooth sharks were caught by local fishermen, Derek Neethling and Trail Witthun, near Struisbaai.

As with the previous sharks (Maxine, Val and Dee), Elle will also be tagged by Dr Malcolm Smale of Bayworld and an AOCA board member with assistance from Mike Meyer from Marine and Coastal Management. The scientists will attach three tags to Elle: a spaghetti tag for long term identification; an ultrasonic tag which transmits a signal for up to a year and whose unique signal can be picked up by base stations positioned along the ocean floor should she pass within 300m of one, and a satellite tag, which will be programmed to surface 4 months after Elle’s release. The satellite tag will gather information on her location; the depth to which she swims; water temperature and daylight patterns.

At the time of Elle’s release, the team aims to tag another two wild ragged-tooth sharks of a similar size so that the behaviour of released captive animals can be compared to that of wild ragged-tooth sharks and to gather much needed information about ragged-tooth populations and their movements along our coastline. The last shark released in 2006, Dee, had spent 14 years in captivity but successfully travelled over 600km eastward of Struisbaai, her release point, over 4 months, compared with the wild shark, Lesley, who travelled more than 900km over the same time period. All sharks released have adapted well to being back in the wild, instinctively following their annual breeding migration path up the South African coast.

To date the M-Sea Programme has successfully satellite tagged 3 captive sharks and 4 wild sharks. The information gathered from these tags has provided the team and scientists with some valuable insights into the lifestyles of these ecologically important coastal predators. This information is valuable in assisting in the conservation of these animals. Each year new information about their behaviour is revealed: the tags on the two sharks last year were programmed to surface 3 months later, but both tags detached early after only 6 to 7 weeks. We suspect that both sharks spent more time in shallow water than we had anticipated which is why the tags released early, said Farquhar. One tag surfaced near the Sundays River on the eastern side of Algoa Bay while the second popped up east of Port Alfred near the small sea-side town of Bira. Fortunately the Sundays River tag was picked up and handed in by a member of the public and the scientists were able retrieve a phenomenal amount of data. The tags record information every two seconds so it is really exciting when a tag is found and returned to us as we then have the opportunity to download all the data rather than just a summary, enthused Farquhar.

Members of the public who are interested in learning more about the Save our Seas Foundation M-Sea Programme and the satellite tagging studies should log on to the AfriOceans Conservation Alliance website www.aoca.org.za.

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