During the first two days we have successfully tagged and released 9 sevengill sharks. Their size ranged from 1.6 to 1.9m. Then on the third day we sailed up to Saldanha Bay, a sheltered and protected lagoon where we found large female sevengill sharks, the biggest one of which was 2.5m long! In total we managed to tag 15 sevengills, all of them were released safely and swam away unharmed. The expedition has totally exceeded our expectations and we couldn’t have asked for better conditions and luck.
We all got to experience what it takes to handle a shark. Your own safety comes first, but safety of the shark is a close second. These sharks are quite strong and powerful, and can inflict painful bites if handled inappropriately. Everything went smoothly however and nobody got hurt.
The tagging procedure:
Shark’s health is always monitored and a constant flow of sea water over its gills is kept. A small incision is made in its abdomen and an acoustic tag is placed internally, the surgery is finished by putting on a few stitches and covering the incision with antibacterial gel. Then a small fin clip for genetic studies is cut. All the necessary measurements are taken. Samples of blood and muscle biopsy are collected. These will help with analysis of hormones and stable isotopes. Finally, a PIT tag is placed under its skin. This microchip is similar to what you put on your pets to identify them. In future, in case of recapturing the same shark, this tag will instantly inform the researchers that the shark already has an acoustic tag inserted.
The shark is now ready to be released back into the water and we all watch as it swims away.
Well done team!
Thanks to the Shark Spotters, Dr Alison Kock, Two Oceans Aquarium and Mike Horn for this incredible opportunity.