Posted on Wednesday, 30 June 2004
Dear Shark Byte readers
I am very happy to report that there is no bad news this month and we have in fact had one of the best months ever at Seal Island. After White Pointer was destroyed we managed to hire a new vessel within days and missed very few days out on the water.
For the first 2 weeks of June we had an amazing group from ReefQuest Expeditions (www.reefquest.com). We have been working with members of ReefQuest since 1999. The aims of ReefQuest trips are not only to educate people about sharks, but also to provide them with the opportunity to participate in ongoing shark research. Expedition group members are chosen by application and they help conduct studies to reveal aspects of the predatory strategies and social behaviours of white sharks. After the day at sea, ReefQuest Expedition group leaders give lectures on different aspects of white shark biology and sharks in general. We always love having ReefQuest members on our boat, as each person shares our passion for sharks!
This group was no exception. The first 6 days started out very slow and although we were seeing a handful of predatory events each morning we went 4 days in a row without seeing a single shark around the boat and the other days were merely what we call “drive-bys”. This means that a shark comes up to have a look at the bait once and then we don’t see it again. The weather was absolutely perfect. In fact it was too perfect and we felt that we needed some bad weather to come thought to shake things up. On Day 8 of the trip it was yet another perfect day and we thought we were in for another quite morning. By 10am we had observed and recorded 22 natural predations and by the end of the day we had seen good sharks around the boat. It was as if a group of new sharks had moved back to Seal Island and the reason for them being here was to hunt Cape Fur Seals. In the past we have mostly observed intense predation on bad weather days. Not only did the good weather continue but the predations that we have recorded up to the end of this month has been a very high amount. The lowest recorded days have been 15 events and on the busiest day we observed 37 events. To give you an idea scientists working at The Farrallon Islands in California, which is also known to be an active great white shark feeding area, record in the region of 40 predatory events per season. This month we recorded a total of 319 events with just under 50% of these being successful for the sharks.
Chris & Rob were the first people to work with white sharks at Seal Island and it has taken thousands of hours on the water to roughly understand what happens in this very special and unique area. Predatory events seem to be more intense just before a cold front, caused by a low-pressure cell, moving into the area. We have observed fewer groups of seals leaving the Island (to feed) and a lot more seals returning. The seals that are most often preyed upon are what we call “Number 2’s”. These seals are approx. 6 to 8 months old and are embarking on their first feeding forays. They usually return alone or in small groups giving the whites an easier target. As they porpoise along the surface their swimming vibrations probably attract sharks that are patrolling in the deeper waters below. Most times the shark will approach the seal with vertical speed, trying to catch it on this first surprise attack. This speed can sometimes propel the shark completely out of the water in what we call a breach.
On the 17th conditions could not have been more perfect with a cold front due to arrive later in the afternoon. We recorded an unbelievable 35 predatory events. Previously the most we had seen on one day was 26 events. This worked out to about one event every 7 minutes. The cold front passed through over night and the following morning we observed another 37 events. On both days the sharks were successful about 50% of the time.
During this intense predatory period we had a fantastic group from South Broward High School, in Ft. Lauderdale, Florida. The trip was organised by Neil Hammerschlag of the ReefQuest Center for Shark Research (www.elasmo-research.org) and supported by a generous grant from the American Institute of Marine Science or
AIMS (www.aimsamerica.org). AIMS, a non-profit foundation dedicated to marine education and research, sponsored ten high school students to spend 2 weeks with us working with white sharks in the field http://www.aimsamerica.org/WFN_SharkTrip.pdf). It was an incredible experience for them as well as a tremendous opportunity that was given to them and we hope
that they will go on to promote sharks as well as the marine environment in the future.
Chris & I have together witnessed in the region of 3 000 predatory events at Seal Island and we can honestly say we have become more sensitive to what we see out there. It is very difficult to explain in words, but the truth of what happens out there is so raw and very, very brutal. On top of having the pressures of mankind both shark and seal have to survive by their own means, and it really is survival of the fittest. The Number 2’s that are 90% of the time targeted by the white sharks are only 8 months old and yet they have that primal instinct to fight their aggressors. They evade the white sharks just more than 50% of the time, and we are so tuned to these events that we can see the determination from both sides to win. As we are top of the food chain I bet most people do not think about the following equation. The seals have to leave the safety of the Island to feed, but to do this they have to run a gauntlet where they in turn may be eaten. And it may not be only one shark that you have to get away from. This month we witnessed the same seal been attacked 4 times by different white sharks while on its way back to the Island. Once this seal reached the safety of the Launch pad a huge involuntary cheer went up from everyone on the boat. But, we have also seen this the other way around where a seal has survived three attacks only to be taken by the fourth shark a mere 100 meters from safety. The only comforting fact for us it that because competition is so high between sharks in the area the seals are consumed within a few minutes and due to the high adrenalin cursing through their bodies they probably do not know what has happened. On rare occasions we will arrive at a predation to find a mortally injured seal that has basically had its hind quarters severed, but it is still fighting for its life. Interestingly, in almost all of these cases the sharks seem to realize that the seal is fatally injured and will go from being in a highly aggressive mode to slowing right down to finish what needs to be done. I guess each ounce of energy counts.
As much as the seals are trying to survive, the sharks are too. Their only food sources in winter are the seals, but this is also represents potential danger for white sharks. Seals can quite easily bite or scratch the shark and should an eye, for instance, be damaged the shark will have huge problems not only hunting, but also heading warnings from their own kind. Seals are also not easy prey to catch and we have noticed that some sharks are more successful than others. Sometimes we can observe just how very good a particular shark is at hunting a seal, and these sharks too show tremendous determination to survive.
I feel extremely privileged to witness this predator/prey relationship that exists at Seal Island. Chris & I try very hard to pass onto people that a predation is not only a spectacular sight, but that both shark & seal need to be seen with the highest respect. It is nature with fatal consequences and when we are out there it is like no other place on earth exists.
Once the predatory activity in the morning quietens down we anchor up to see what sharks we can draw to our boat. We know from the predations that there are many sharks in the area, but we have been seeing the same 10 or so sharks around the boat. Most of this month we have not been chumming, just as a test to see if it makes a difference. Rob has been chumming and we have been getting the same amount of sharks and sometimes more than he has. We have not seen too many of the sharks that we see from year to year. We are only about half way through the season so there is time yet for them to show. In the meantime we have got to know a new batch of sharks. Without fail each day we have seen a 3.4 meter female shark now called “ Scratchy” due to a scrape around her nose. She is very domineering and whenever another shark comes to the boat she arrives too, seeming to tell it “hey this is my boat!”. We have seen “February” who we last saw in February 2002. She is in great condition at just under 4 meters in length with an awesome presence about her. She is also very confident and we have to take extra pains not to let her get the bait from us. Another great shark we have seen a lot is “Cuz”. He is an average size male, but likes to do a few tricks that Rasta does. For instance he will just swim up to the boat and stick his head out! When we have great weather it is very easy to see the sharks as they swim around the boat and the high school students have been able to get very good ID markings for all these sharks.
Hopefully we will see our new friends as well as a new batch of sharks in July!
On the “Photo’s of the Month” I have put up a lot of new natural predations images that Chris had taken as well as some new breach images. There is one breach in particular where the shark is about 3 meters clear of the water…it is the highest we have ever seen a shark breach and really worth taking a look at.
Until next month,