Friday, July 23, 2010
Shark Chronicles 71 - Raggies at Aliwal
Since the last time we blogged, the weather has greatly improved and we were able to go back to diving! Last Saturday and Wednesday, we did two “shark” dives. The visibility has gotten much better, which is really helpful for the measurements we are trying to do on the blacktip sharks. We have been using two lasers and a video camera to determine the sizes of different individuals. Meanwhile, some of us are taking notes on distinctive features of some individuals so we can identify them later on.
We have also been trying to determine potential feeding behavior and hierarchy among the blacktips with the help of an HD camera. James free dives to the bait drum, gets 4-5 sardines and throws them away from the bait. We are then filming the feeding behavior of the sharks and hoping to see dominance from certain individuals.
Despite the good visibility and the lack of swells and currents, the water temperature has been pretty low – around 21°C -, which is probably why the tiger sharks are not showing up to feed.
We also went back to the site called “Raggies’ Cave,” and used the lasers to determine the average size of individual ragged-tooth (raggies) shark. There was very little current, which was really helpful for taking the measurements and pictures. On Monday, we had the opportunity to dive the Nebo shipwreck, sitting at approximately 30 meters deep. We got to explore inside the wreck, which was pretty fun! There were no sharks to be seen, but a lot of rockfish, scorpion fish, lobsters and a lot of juvenile fishes using the wreck as protection. A big cuttlefish even came our way during the dive and we got to observe the fast-changing colors of this animal.
The marine life on the Shoal is very interesting and abundant; we had the chance to see some loggerhead sea turtles swimming around us during the dives, but also common dolphins or humpback whales swimming along the boat.
We had a “day-off” last Friday, so Ryan and a couple of us drove to Durban to go to the Sharks Board. The Sharks Board has been designed to educate people about sharks present in the region, such as tiger, ragged-tooth, oceanic blacktips, hammerheads, bull, whale and even great whites. They do shark dissections on some days but not on Fridays unfortunately! We also went to the big uShaka Aquarium, which is set up in a shipwreck. We had a really good time, discovering the marine life of the whole East coast of South Africa. We were already impressed by the size of the ragged-tooth sharks we see during our dives, but the ones there were gigantic!
We now have a couple of days off before the start of our last week here in Scottburgh. We are probably going to use this time to organize our data, finish the reef-check certification or even perfect our surfing skills!
Christina Marmet - Aliwal Oceans Research intern