Posted on Thursday, 31 July 2003
Hello Shark Lovers!
We have had an interesting month where most of the month has been very slow compared to what we usually see, but towards the end of the month activity has sky rocketed, taking us all by surprise.
Up until July 25th we were observing what had been happening the whole season so far, whereby there were very few predations. When sitting on anchor waiting with bait out, we were seeing far fewer sharks than we should see for our peak season. The prevailing summer wind was blowing everyday, as opposed to the N.W that is supposed to blow.
Around July 25th the synoptic charts picked up a cold front on it’s way to Cape Town and the days leading up to this approaching front seemed to provide the sharks with the ideal hunting conditions that make them so successful.
We seem to think that both the seals and the sharks are able to sense this bad weather approaching. When the weather is good the seals leave the Island to hunt throughout the day.
Now, suddenly only 4 groups left in four days and the only seals left to run the gauntlet where the seals returning back to the Island. The sharks also seemed to return in mass. The whole month we had been averaging 5 different sharks up at the boat per day. On the 25th our boat and Rob’s boat anchored at different ends of the Island. Rob said that before he had even put his anchor down there were 3 sharks that he could see. (This is probably due to the sharks investigating the noise that his boat would have made.) We also recorded 13 different animals that were at our boat in a three hour period. This particular day was outstanding…
As mentioned in previous shark bytes’ another of our favorite animals is Black-white-black. We have recorded seeing him over 50 times and have gotten to know his personality very well. He is extremely dominant, confidant and aggressive. He also seems to be one of the more intelligent sharks that we know. We had not seen him the whole season and between Chris & myself we were extremely worried about him especially as we usually see him so often. We needn’t have been as he was the first shark up at the boat on this day! Chris and I were so excited and relieved to see him. He was just the same as always and so fast in approaching the bait. At one point he was 10 meters from the bait when I saw his powerful tail do two swipes to build up speed. It was a good thing that I noticed this as I barely got the bait out of the water in time. Ten minutes later a second shark arrived and she turned out to be Rasta! I couldn’t believe it. Everyday since Chris had seen her in early June I had hoped that she would come back and now it felt unbelievable to see both her and BWB together. You actually can’t see two more different sharks together. Rasta would be so slow moving to the bait that she almost lulls you into giving it to her and then on the other hand there is the speed-demon BWB. I really had my hands full!
BWB does not look like he has grown at all since last year. He also has a lot of parasites called copepods on his body and his tag is full of growth. This could mean that he has been spending his time in warmer water. He would have come specifically to Seal Island to feed on seals and we have observed him to be very successful at this, so we hope that his condition will improve.
Rasta on the other hand is enormous and has grown considerably in the past year. Getting a better look at her we reckon that she is close on four meters now. When Chris first saw her in 1997 she was 2.5 meters. It has been so rewarding to see her mature into a healthy and very formidable super predator.
I always say that anybody who sees her can’t get over her relaxed nature. Whenever she comes near the boat she will put her head out and when I watch her eyes it appears that she is looking at us. I wonder what she thinks!
We recorded 10 other sharks at the boat on this day and on a few occasions we could see 5 sharks at once. They really do not like being too close to each other and in these circumstances one can see great interaction between them. This will usually mean very quick bursts of speed as the less dominant animal gives way.
The following six days turned out to be phenomenal for natural predation on seals. On the 29th we recorded 23 events. This is one of the busiest days we have ever recorded. At one time we had 4 events happening at one time and as we would be racing over to one someone would shout that another was happening. It was crazy. At one of the predations we saw Rasta in pursuit of a seal and on this occasion she was deadly accurate.
The following day the core of the front hit False Bay. When we woke up in the morning the wind was just beginning to build with intensity so we though we could get out for a few hours. When we arrived at the Island the wind was at about 30 knots and the sea was extremely turbulent. It became a very worthwhile trip as we observed 10 predatory events in a very short space of time. Of these, eight were successful kills. Once an attack was in progress huge plumes of water would explode into the air, more exaggerated than normal due to the rough water and high winds. It seems that these conditions provide the perfect recipe for hunting sharks and they are there to make the most of it.
Again, we only observed seals returning to the Island, particularly seals that are in their first year. They would be very inexperienced and in the foul weather it looks as though they are desperate to return to land. The rough waters, as well as the cloud cover that does not allow light through, must make it almost impossible to pick up on an approaching shark.
When a shark makes a successful predation on a seal they are highly efficient and the meal is usually over in seconds. Added to this the seal would be emitting huge amounts of endomorphines and would probably not feel the pain. It is a very humane way to go, but it still does not make an easy event to witness. As much as we love the sharks, we do also hold tremendous respect and affection for the seals.
It is, however, this predator/prey relationship that makes Seal Island the very unique and special ecosystem that it is. Do the sharks know that they will get easier meals in these conditions or is it just coincidence? I think we all need to give nature more credit than what we do. I also think that there is a very sensitive balance that exists that must be treated with the utmost respect.
Below, please find the statistics for July:
Successful predations: 50
Unsuccessful predations: 67
Sharks success rate: 42.7%
Smallest shark seen: 2.3 meter female
Largest shark seen: Rasta! 4 meter female
I look forward to sharing our experiences with you all next month.