August 2003 Shark Bytes
Posted on Sunday, 31 August 2003
August has (finally!) brought with it the Cape Town winter weather which in turn seemed to bring about very good conditions for the sharks to predate in. This was very relieving for us to see as the previous months’ activity has been so much lower than what we usually observe.
In fact, this August we have recorded the highest number of predatory events since working at Seal Island in 1995! We recorded a total of 247 attacks with 145 of those being in the shark’s favor. That is about a 70% success rate, absolutely phenomenal, even though the great white shark is one of the apex predators of the ocean. On average the success rate is usually between 48 and 52 percent.
What has made a big deference in collecting data is that we were fortunate enough to have a particularly enthusiastic group with us who came to Seal Island specifically to see this natural predation. When the conditions at sea were uncomfortable due to bad weather, they still wanted to be out there. When these stormy, cold fronts were hitting we recorded many, many successful kills. These rough conditions definitely seem to aide the sharks.
I have learned so much at Seal Island over the last four years, but what has to be one of my greatest lessons is that Seal Island is not just about great white sharks. It is about the entire eco-system that exists there. There are roughly 60 000 seals and everyone of those seals have to head out into the Bay and most times, even further off-shore, to feed. To do this they have to depart and return to the Island over areas where a great white shark could be stalking from the depths undetected. Should this happen, the fight of their lives is on. When I say “their” I am referring to both shark and seal for this battle of survival is just as important to both. On top of all this the black-backed kelp gulls, which co-exist with the seals on the Island, are also there to survive. They may sleep beside the seals, but they are also waiting for them to die. A large part of their diet consists of the small bits of seal that are not consumed by the shark. The gulls watch and wait on an elevated area of the Island that happens to look out over the most active predatory area. I am quite sure this is not a coincidence. From here they are able to detect any possible attacks. They pick up on the predatory indicators so quickly. We can now even tell how confident they are over what they have seen by the way they fly. Once they arrive at a successful predation area a massive fight breaks out between them and it seems whoever is able to swallow the quickest will get the most. If they so much as hesitate, the piece will be snatched from their beak by another hungry bird.
We are now learning that this sensitive eco-system does not only need the animals for everything to work, but the weather also plays an extremely important role. If there is a storm approaching, the seals still have to go out to feed even if they are in greater danger from the sharks. I guess this is something to think about the next time we are curled up in front of the TV with a mug of hot chocolate on a stormy day.
Even though we were seeing so many sharks on predations, we surprisingly really struggled to get sharks up to the boat when we were on anchor. The sharks seemed to be completely disinterested in the bait and if they did show up at the boat it would only be for a few short turns.
We were lucky enough to have Rasta at the boat four times. We rarely see four meter-plus sharks at Seal Island and as Rasta is approaching this size we really make the most of appreciating this very special animal. We feel it is such a privilege that we have been able to spend so much time with her already.
We also saw NotchFin and Staywith, but at predations only. The other Seal Island locals seem to be scarce, but it is always very difficult to identify sharks at predations as it happens so quickly.
A very spectacular sight we sometimes see is what we call a natural breach. This is when a shark will breach out of the water for apparently no reason. These are the most unbelievable athletic feats you will ever see a shark achieve as they seem to launch themselves higher out the water than they usually do. A natural breach will only happen once so you just have to be looking in the right spot at the right time. It can be very frustrating if you miss it as everyone else will be hollering in great excitement! On one of the days this month we were sitting on anchor, waiting for sharks when Chris decided to take a photograph of the scene using a wide angle lens. As he was looking through the viewfinder a natural breach happened about 5 meters behind the boat! Chris managed to take the photograph of all of us in the foreground and the shark in mid air behind us. Because of the wide angle lens the shark in quite small, but you can definitely see what is happening. I think the chances of ever capturing another image like this one would be virtually impossible!
Since June this year we had been watching a “green seal”. This seal had a large piece of green trawl netting around its neck as a result of coming into contact with fishing nets. Unfortunately this will mean a very slow death for the seal as it will be very difficult for it to catch fish, meaning starvation, or it could be as bad as strangulation as the seal grows. We would see this young of the year pup almost everyday. In June it was still very healthy but by the middle of this month its condition had noticeably worsened. On the 23rd we had an opportunity to free the animal and Chris managed to do this successfully. It was so rewarding to watch the seal come free after so many months of struggling. This does unfortunately happen too often, but we do our best to rescue these seals should we come across them.