Shark Chronicles 007 – Following the paths of the Great White Shark
As anticipated in the last blog episode, SAMPLA has tagged its first white shark, a female of 2.7-2.8 meters (around 9 feet) long, which we named “Sampla”. The acoustic tag was deployed from our research vessel Lamnidae by SAMPLA’s technical director Stephen Swanson at 11 am on 17th March 2008. It was a memorable moment for SAMPLA as it represents the beginning of SAMPLA’s data collection via acoustic tracking. We hope it will give us greater insight into the ecology of the white shark including providing information on the white shark’s habitat use, swimming depth preferences, and movements along the Mossel Bay coastline. The multitude of beach goers over the weekend appeared blissfully unaware of any white shark presence, as, or so it appeared, was the sharks to the presence of the beach goers. Despite the current peaceful coexistence of sharks and water users at MosselBay, it remains important for science and for the public to know where the sharks are!
The excitement and anticipation surrounding the tagging of SAMPLA’s first shark put the pressure on the SAMPLA field team, but Stephen’s arm was steady and our ‘first lady’ (nothing to do with Washington!) shark swam away, tag perfectly set. The acoustic tag emits a sound signal at approximately one second intervals over several months, and will allows us to follow the shark “Sampla”, by using a hydrophone (an underwater receiver with headphones). Subsequent to tagging Sampla, we set up the hydrophone and after allowing her ten minutes to settle, we started to track Sampla.She showed no signs of adverse affects from the tagging, and even came to investigate the boat (white sharks are curious) before resuming her sub surface course (we try and maintain a distance of not less than 20 m to reduce the effect of the vessel on a shark’s behaviour).
A great deal of excitement was generated by the tagging of Sampla. Where will she go, will she stay in the bay and allow us to track her? In 2005, current members of SAMPLA successfully tracked white sharks which stayed within the bay for 5-6 months, but Sampla is a new shark in a new year and tracking her could supply us with new information and/or new problems! The dilemma now is how long Sampla will stay in Mossel Bay? Our research vessel is not massive (6.5 meters – 21 feet long) and, like its crew, it is not equipped for long journeys in the open ocean. Within these restrictions (i.e. as long as Sampla remains in the bay) we will do our best, with the use of shifts and different tracking teams, to follow Sampla for as long as possible. Ultimately, the vagaries of nature do not allow us to dictate the terms by which we can track a shark!
Our next post will reveal the story behind our first 24 hour tracking of SAMPLA…