Posted on Friday, 8 May 2015
April 2015 is definitely echoing the pattern of the dreaded April of 2012 … our sharks are currently missing in action!
So, in this Shark Bytes I will briefly update you on our April Great White shark sightings as well as water conditions that could possibly be having an effect on our shark sightings.
I will also be sharing a fantastic experience we had with a large pod of pilot whales recently off Cape point.
Finally, you’ll find info on Chris’s upcoming talk, Amazing Moments with Wildlife, on 20 May at The One & Only Hotel in Cape Town.
Great White Shark Sightings
As I sit writing here on 6 May we are now into our 22nd day of no sharks at Seal Island.
It was an impressive crash… The entire month of April up until 15 April was fantastic. We finally had periods of good weather, the water visibility had improved and we were seeing between five and eight sharks per trip. The crew were super positive as we began to head closer to the peak part of our season and the very interactive sharks around the boat were giving all our guests a great experience both cage diving and viewing from the surface.
On the 14th of April we had a total of seven sharks, all interactive, and all the signs were that sightings would continue this way. Then seemingly out of nowhere the trip on 15 April saw no sharks. It was a complete shock! We thought that this may have been just an abnormal day but we had the same result on the following trip and by this point we realised that something had gone out of whack.
Keeping guests informed of the situation, and with various options given, some guests have chosen to try over the last two weeks and unfortunately still no sharks…
Many theories are now being thrown around and I guess the simple answer is that this is nature, and you can never be guaranteed of anything. For sure there is a good reason for this change at Seal Island, which makes complete sense to the sharks, but may be beyond our understanding.
Dead Water Areas
I did spend some time in February Shark Bytes talking about upwelled water and how this nutrient rich water caused bad water visibility conditions. Again, we think that the root of our sharkless problem is coming from here.
We recently read about a study conducted along the west coast of Africa where areas of water were discovered that were so seriously deficient of oxygen they became Dead Zones. Dead zones are areas of the ocean depleted of oxygen where most marine animals were not able to live. Dead zones are most common near inhabited coastlines where rivers often carry fertilisers and other chemical nutrients into the ocean, triggering algae blooms. As the algae die, they sink to the seafloor and are decomposed by bacteria, which use up oxygen in this process.
If we understand the above we can possibly equate it to the situation in False Bay. The city with a population of 3 million plus people flanks the Bay with many storm water, sewage and untreated water runoffs creating an ever increasing nutrient load being emptied into the Bay.
From the upwelled conditions the nutrient levels were already high. What followed was a period of settled warm weather with very little water movement, ideal for solar radiation causing a massive algal bloom and what looked like red tide conditions. This could have given rise to an algal die off which then sinks to the bottom and is consumed by the bacteria. The bacteria in turn thrive, consuming vast amount of oxygen and creating large pockets of oxygen deficient water. With current conditions of small swell and low winds there is still very little water movement in False Bay and it is likely that the current situation may continue until weather conditions change.
These ideas are our speculation only but we know from various studies conducted that highly active predatory sharks such as great whites require large amounts of absorbed oxygen and as such will be particularly affected by oxygen deficient water. As such we feel that any great white shark is not going to choose to spend time in an area where conditions are not ideal and possibly even life threatening at a stretch. Great white sharks have extremely large gills indicating the need for large amounts of absorbed oxygen which is then transferred into the blood stream. These sharks have huge muscles which give the sharks the capability of tremendous short bursts of speed and as such these big muscles require vast quantities of oxygenated blood to drive them. This all demonstrates why highly oxygenated water is so important to a great white shark and why they would avoid oxygen deficient areas.
Our 47-days-of-no-sharks record from 2012 is definitely a record we do not want to break so perhaps for a change you call all send us bad weather vibes to try and shake up some change in False Bay!
Pilot Whale Encounter
Coming across a pod of 70 longfin pilot whales off Cape Point has definitely been not only the highlight of this past month, but possibly of the whole year so far. An extract is below but you can read the full blog here.
“10 miles into the journey home I spotted two small spouts in the distance. As we approached the two spouts had increased to at least ten… it was a pod of long fin pilot whales!
Chris, of course, immediately decided to try get in the water with them. I declined… after all the experience of being rushed by a large bull several years back didn’t exactly put me at ease and the thought of diving with them had me edgy.
We positioned the boat ahead of the approaching pod and Chris gently slipped into the water. He soon had the whole pod gently cruise by him. After his exhilarating experience I quickly forgot my anxiety and along with two other friends who were on board we readied ourselves for an incredible experience.
As you first slip into the water it is a strange and daunting experience being out in the open ocean and swimming over 1500 meters of blue water. Coupled with an approaching pod of pilot whales, one’s heart is racing in anticipation. We were not to be disappointed as our small group of snorkelers all stopped motionless in the water and watched as the pod passed us by.
The water visibility was about 20 meters so we could see way down below as the shyer animals dived to deeper water and of course to be just a couple of meters from the bolder ones on the surface was amazing.
The pod was moving at a fair pace and after surfacing from this swim-by we looked into the distance… more spouts! This time round there seemed to be many more animals and the pod we were currently with must have been a splinter pod heading for the main group. We decided to head for the larger pod ourselves.
The numbers seemed to swell in the two hours that we spent with them and we estimate the pod numbered between 50 and 70 individuals. It was difficult to tell as with each dive many more could be seen swimming below compared to what we were seeing on the surface.
It is not possible to keep speed with the pilot whales so our “dives” consisted of the boat dropping us in front of a tightly knit group and having the whales pass by if they chose to.
Each time we saw interesting behaviour. They were definitely aware of our presence almost as soon as we got in the water (they would have picked us up using their sonar) and most would dive to about 5 meters below.
The calves would stay very close to their mothers and I also observed on a number of occasions three pilot whales swimming three abreast tightly alongside each other.
Many of them were curious and as they approached us would swim upside down exposing the white vertical flash that runs from their chin to tail on the under belly, all the while closely looking at us. Others would turn on their sides slightly and we could clearly see the white outer-rims of their eyes as they reticulated their eye balls to try observe us better. I think this was the highlight for me… being able to clearly see how interested they were in looking at us, and seeing the intelligence behind those questioning eyes.”
Amazing Moments with Wildlife, Talk at One & Only Cape Town
Chris will be speaking once again at The One & Only Hotel in Cape Town in a couple of weeks’ time.
His highly visual presentation will focus on sharing some of his most intimate wildlife highlights with animals across the planet, followed by a delicious dinner at Rueben’s Restaurant in the Hotel.
Full info on the talk and how to book can be found below:
We hope to see some of you here on 20 May at 6pm.
I am sure that many of you will enjoy hearing from Jimi Partington, our shark guide and dive master on board White Pointer 2, so please check out his latest blog Diary of a Shark Handler here.
Photos of The Month features some beautiful images of the long fin pilot whales during our incredible dive with them… we hope you all enjoy.
And lastly, don’t forget to look at The Great White Trail, our great white shark expedition in August that takes in all 3 Shark Hot Spots in South Africa. All other expeditions are full for 2015 and there are just 5 spots remaining on this August trip.
Until next month.
To read our last three Shark Bytes follow the links below:
March 2015 Shark Bytes
February 2015 Shark Bytes
December 2014 Shark Bytes