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Dyer Island White Shark Research Blog #4 - 06 May 2010
by DICT's Marine Biologist Alison Towner
Shark Blog 4
The last few weeks have seen the beginning of an exciting new phase of research in Klein Bay which that will help us to understand the behaviour of the great white sharks here for the first time. Things are coming together nicely with new equipment, discounts, donations and team spirit!
Research Team Gain New Scientific Device – A CTD!
Measuring white shark movements in relation to environmental parameters is certainly easier said than done! However, thanks to one of our scientific supervisors, Dr Malcolm Smale of Bayworld in Port Elizabeth, the first phase of the inshore shark project has begun. Malcolm kindly permitted the research team to use his CTD which as the abbreviation implies measures water conductivity, temperature and depth.
After an in depth training session from Malcolm’s research assistant, Michelle du Toit, the team went into the field to sample water within the Bay and around Dyer Island. We sampled four sites inshore, one in Shark Alley itself and one just over the Geldsteen side of the Island (a well known area for the sharks in winter).
The graph (above left) may look like three pretty ordinary lines to most folk but in fact these are extremely accurate plots of the turbidity (red line), salinity (blue line) and temperature (green line) at sample site 6 of our transect test grid – just outside the mouth of Shark Alley. Such water sampling has never been previously conducted in Gansbaai. Furthermore, the plots paint a picture of what’s going on down the entire water column right to the sea bed as opposed to just surface data. They provide a really detailed picture of favourable conditions for sharks and why they might spend time in some areas of our bay instead of others at certain times of the year.
We are privileged to have use of such a fantastic piece of equipment, from both oceanographic and biological points of view. We are thrilled to see the results over-laid with the shark tracks – specifically in the summer months.
Special Discount - Vemco Equipment
Canadian telemetric corporate Vemco has chosen the inshore shark DICT project proposal as a winner telling us:
“Congratulations your proposal has been selected to receive the student discount offer”.
To actively tag and track a shark is a costly process. One has to first purchase the acoustic tags, which cost up to US$ 600 a piece. Then there is the implementation of the tag on the shark and actively following the animal by receiving its signal. Once this is done the data has to be downloaded, which involves extensive/expensive software and time. So you can imagine the Trust research team’s delight when we received an email on 20th April telling us of the award more than halving the normal ZAR 60,000 cost of a vr100 kit plus tag. This massive saving in costs is great news and fills us with even more confidence in the project!
Marine Dynamics Continue To Have Excellent Autumn Shark Sightings
What a wonderful month shark wise! We have had lovely warm water up to 17 degrees Celsius during much of March and April. The sharks have been around in vast numbers with large males and females sighted regularly around the island. On one occasion there were seven sharks in view at one time. A shark we were quite thrilled to see the return of was Big Nemo. This shark has a distinctive hole in his dorsal fin. Oliver Jewell identified the fin in a catalogue from being satellite tagged in Mossel Bay in 2003. The tag as it aged on the sharks dorsal fin gathered a lot of algae on it, and as a result caused quite a distortion to the fin. Nonetheless the shark is extremely active and always a pleasure to interact with at sea.
Sharks Need Your Support
Shark sales are going really well, we have reached over ZAR 73,000 so far, which means we certainly can buy our own tracking equipment, made even more possible with this new offer.
The film crew from German’s Planetopia, supported us by buying 30 spaces – ZAR 4500. Watch their production on German television 10-11th May.
Now we just need continued support to keep buying tags – and every little bit of support really does go a long way. We hope to fill our spot map completely before the soccer World Cup!
Please do think about helping us and donating
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| WOUND HEALING VIDEO AND POSTER |
| We have uploaded some amazing footage on the incredible capability of the great white to heal from injury. This poster was presented at the International White Shark Symposium held in Hawaii in February.
You can read all the details and watch the footage here. |
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Plots of the turbidity (red line), salinity (blue line) and temperature (green line)
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 Plots of the turbidity (red line), salinity (blue line) and temperature (green line) |
The return of Nemo |
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