The toilets at the Simons Town jetty are currently closed for renovations as I understand it. They are due to be ready soon but I do not have a date. Also note that the Wharf street parking at the jetty is again a paid parking area for the season.
It may seem that given the week-long south easter we are having, it would be a simple matter to decide which side of the peninsula to dive. The picture was taken from Chapmans Peak drive today around lunchtime, and the water is not very clear – there are rocks just below the surface in the little bay below the road, but they are hardly discernible.
The water colour in False Bay is not very different but False Bay does seem to recover faster than the Atlantic coast of the peninsula. Sunday’s forecast is for gale force winds, so Saturday is the only decent diving day, but where?
Depending on tomorrow’s wind direction I will make a call late in the afternoon on whether we will launch in False Bay or out of Hout Bay. Either way it will be for dives at 10.00 am an 12.30 pm. I will have mostly Open Water students so the maximum depth will be 18 metres.
We are in a phase of semi-decent weekday diving and dodgy weekends again. We had fairly good False Bay diving during the week, but the weekend forecast is not ideal for much beyond storm chasing. Strong winds and some significant swell topped off with a dash of rain are hardly a cocktail for diving. Northerly wind is not that great for False Bay and neither is a 5 metre swell, so best you pursue some other form of activity this weekend.
One of the guys in the Underwater Cape Town facebook group reported a sighting of a john dory at A Frame this week. These fish are striking, solitary, and seldom seen. Bizarrely for such an exotic-looking fish, they are popularly served wrapped in newsprint with a side of chips. We were lucky to spot one at Long Beach a few years ago. (Go check out the video on Underwater Cape Town for a better idea of what they look like, and keep your eyes open next time you go diving!)
Talks talks talks
This Wednesday 17th is the nautical archaeology talk I mentioned in last week’s newsletter. There’s a talk on 23 August about the health of our fish stocks by scientists Colin Atwood and Jock Currie at Bellville Underwater Club – info on facebook. If you have a UCT staff or student card, you can listen to conservation photographer Thomas Peschak speaking on 21 September – info on facebook, too.
I completed the edX-hosted Sharks! MOOC, presented by Cornell University and the University of Queensland, and it was excellent. The content was clear and for me, who stupidly quit high school biology at the age of 14 for the sake of a more classical (less useful) education, filled in a large number of gaps in my understanding of sharks and rays.
A long period 3 metre swell arrives tomorrow, drops on Saturday and then builds again on Sunday. I am planning two launches early on Saturday morning as I have several students to certify. We will meet in the car park at False Bay Yacht Club at 8.00 am. Destination unknown and weather dependent. If you’re keen on a magical mystery tour, drop me an email, text or Whatsapp.
Maritime archaeologist John Gribble is speaking at the auditorium of the South African Astronomical Observatory on Wednesday 17 August, 4.30 for 5.00 pm. His talk is entitled “From Shipwrecks to Hand Axes: An Introduction to South Africa’s Maritime and Underwater Cultural Heritage” and is described as follows:
South Africa’s maritime and underwater cultural heritage is surprisingly diverse and extremely rich. Although shipwrecks are the most obvious elements of this rich heritage resource, there are a range of pre-colonial maritime heritage resources that are less well known. This talk will introduce South Africa’s maritime and underwater cultural heritage, highlight the archaeological importance of this resource, and touch on a few examples of interesting, local historical wrecks.
There is no need to book, the event is free to the public.
If you’ve been on our boat, you may have noticed that I always wear a life vest. It’s a slimline one that we purchased in Denmark a few years ago. The vest contains a small gas cannister with a pellet (looks like a headache pill) that releases the gas in the cannister and inflates the jacket when the pellet gets wet enough to dissolve.
When we went back to Copenhagen between Christmas and New Year, we purchased replacement cannisters, thinking that for safety’s sake it would be wise to service our life jackets to ensure that when we need them, they’re in tip top condition.
The question then arose as to what to do with the existing, unused cannisters in the life vests. Since you can repack the vest with a new gas cannister and dry pellet after deployment, and neither Clare nor I had seen one of these life jackets in action before, we decided to let it fire off in the swimming pool. Here are the results:
It definitely renewed my confidence in the life jacket, an important component of our safety gear, and (as you can hear in the video) provided some significant entertainment for my camera person Clare.
Staying with our informal theme of the last few weeks’ (admittedly sporadic) posts, let’s look at a recent article from the New York Times Magazine. Not solely focused on marine animal studies, the article explains how technology has enabled even the general public to directly observe and learn about the migrations of birds, sharks and other animals. The utility of this kind of information is obvious:
By discovering the precise routes animals take during migration, scientists can assess the threats they face, like environments altered by habitat loss and overhunting.
The article’s author is brilliant nature writer Helen MacDonald, who wrote H is for Hawk, and she goes on to muse about the meaning of the relatively few individually tagged and named animals which become icons of their species as they appear to transverse a simplified, borderless planet in solitude. (The OCEARCH sharks on their satellite map refer!) It is easy to lose sight of the rigours of the environments they move through, but easy to become invested in the future of particular individuals.
After a few days of rain and southerly swell False Bay does not look that great. This swell direction is set to stay for a few more days and in fact changes only on Monday. There is some south easterly wind on Friday and Saturday but not really strong enough to clean up the Atlantic enough for decent visibility.
I think it may well be a dry weekend as far as diving is concerned, however if things start to look more promising than they currently do, I will be in touch. Let me know if you’d like me to message you if we go diving.
Did you pick up the July edition of National Geographic to read about great white sharks, or read the article online? (Pro tip: you should.)
The article’s author, science writer Erik Vance, contributes to a blog that I follow called The Last Word on Nothing. I was delighted to read a follow-up he posted to his National Geographic feature, explaining how scientists count sharks. At the heart of the method is a beautiful piece of statistics (a model) that allows scientists to draw conclusions about the size of a population – some of whom are tagged or marked – based on only a sample of the individuals, and what proportion of those sampled individuals is tagged.
Why is it important to know how many great white sharks (or cowsharks, or whale sharks, or or or…) there are? The most obvious answer relates to conservation: if we have a baseline population estimate, we can then determine whether it is increasing or decreasing over time. What is the status of the population? Are these animals endangered, or flourishing? Are conservation measures necessary? Are they effective?
Go and read about counting sharks here. An important thing to pay attention to when you are reading any scientific model is what the underlying assumptions are, because they will show you the circumstances under which the model will fail.