Spoilt for choice!
August 14, 2011 by dyertrust
I think the sharks must have started reading our Marine Dynamics newsletters. In July we left off hoping that our sightings would improve and that we would see at least one more spell of activity at Dyer Island again before winter season draws to an end. After a very dry sharky phase at the Island in July, just as we hoped, a new set of fins appeared there this month! The nice thing is, the sharks seem to have divided themselves between the inshore reefs of Jouberts dam and the island leaving us seriously spoilt for choice on where to anchor!
Even though winter months are usually rated as our best time for shark viewing, my personal favourite time of year is the end of August/September. This is spring in South Africa, and we generally see big female sharks inshore. Even though our visibility is often compromised, the sheer size and attitude of these big girls makes up for it. Each shark seems to have an awareness of its own physical size and power and they often circle our vessel in such a deliberate and graceful manor. When juvenile sharks dare to arrive at our boat, it is so amusing to see their behaviour as they spend most of their time holding back and giving way to the bigger more dominant females. On the 8th of August, not one shark was less than 3.5m, with most of them measuring in at the 4m mark. Our team are starting to recognise the same fins returning to the shallows each year, and it seems these big females show site fidelity to the beach here in Gansbaai, meaning that they are homing back here to rest, socialise, passively feed- avoid harassing males- or all of the above!
Whopper!
One of the largest sharks ever sighted from Gansbaai’s cage diving vessels appeared on the end of July. She was sighted again at our vessel Slashfin on two more occasions in the first week of August. We suspect she was either seriously well fed, or due to her extremely rotund belly, she could even have been harbouring a small litter of pups in her belly (-optimistic- but there’s always a chance!). We know a female white shark generally needs to be over 4.5m to give birth. Some have measured in over 5m and are still only just mature according to records from the North East Pacific. However, this shark had been sighted last in our area during 2009 and on return; this month had doubled in size and width. Some boats placed her at 5m; we measured her in by our dive cage at least 4.5m. Nobody has ever documented white sharks breeding before- as other huge white sharks sighted in this area, she was only seen on a few occasions and then presumably moved off. If only we could have taken blood samples!
Familiar fins
Betty so called after the US TV show Ugly Betty returned and was sighted in the shallows on the 18th of August. She got the name from a nasty scar she has which makes her look quite menacing when she opens her mouth. She also has a distinctive lunar shaped cut out of the top of her caudal fin along with an invasive calanoid copepod infestation, which appears to breeding in her snout! Unfortunate in the aesthetic department, she makes up for her looks with her casual and inquisitive behaviour circling the decoy and bait line for long periods. She is definitely one of the more cool calm and collected sharks we know. I first photographed Betty in March 2007 at Dyer Island and she is one of the few females we see at both winter and summer locations. Her visits to this area are usually brief, and the last time we logged her was at Dyer Island at the beginning of the year.
Demon- is another big female, we last saw in 2009 according to our database. Her fin has changed slightly as she now has a small shark bite out of it! This injury does not slow her down however, and she got the name from the way she ambushes and lunges, often rocketing out of the depths before you can prepare yourself for her! Demon was also sighted in July at Dyer Island, along with a couple of times recently in the shallows. It is always so nice to see sharks we know return as it gives us peace of mind to know they made it alive for another year.
Oli registered!
Oliver Jewell, our MD biologist/research skipper has recently visited the University of Pretoria to defend his research proposal. Oliver is looking at shark behaviour around Dyer Island, and wants to continue with his studies into 2012. His presentation to the biological sciences department was a big success as he is now fully registered and ready to go! Olis supervisor Marthan Bester came to Gansbaai and paid us a visit, he even managed to join us on a tagging trip on Lwazi. Marthan is hugely respected in the scientific arena, and spends up to 14 months at a time on the sub Antarctic Marion Island collecting elephant seal and other marine mammal data. It was a pleasure to have him here with us- and to hear his fascinating stories!
The winter cold fronts are starting to arrive now bringing big swells to the bay. For this reason, we have not been able to deploy another tag on to a shark, but we are waiting for a clear gap for tracking, so standby. Until next month, let us hope our sharks stay spoiling us!
