I am short of time today so I will be brief and to the point. Sunday looks like the best option for diving, and Hout Bay looks like the best location. Text or email me if you are keen to dive.
Reports are that the sevengill cowsharks at Millers Point have cautiously reappeared – I think they’ve possibly been absent since March! We look forward to verifying the reports when False Bay’s visibility is a bit cleaner.
Sunday: Early morning double tank dive, location to be confirmed
Conditions last weekend were pretty good. Not much wind or swell and decent visibility. The wind and swell for the weekend ahead look great with very little of either. False Bay, on the other hand, looks a little messy from some humping south easterly wind today.
The wind dies tomorrow and stays away for the weekend. I don’t doubt that both False Bay and the Atlantic will offer decent diving if you take the time to check before you choose. I plan to launch on Sunday as early as possible for a double tank dive somewhere clean. I have family arriving at midday from abroad and want to be done by then. If you are up for a early dive let me know and I will add you to the list.
The Shark Spotters mobile app is available – search for Shark Spotters in the Apple app store or Google Play store and download it for free!
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.
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.
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.
The cold front seems to have passed by and the second one that was meant to arrive tomorrow seems now to be giving us a miss. We had 40 mm of rain at home on Thursday, for which we are grateful. The break in the weather means there is a good chance some diving might happen this weekend!
I am going to shore dive on Saturday at Long Beach and launch on Sunday, the first dive being to the Brunswick, meeting on the jetty in Simon’s Town at 10.00am. The second dive will be at 12.30, the location weather and viz dependent.
I know we are barely past the halfway mark of winter, but the last few warm and pleasant days have got me wishing summer was here.
Some swell and lots of south easterly wind are in the forecast for Saturday, so Sunday will be the better option for diving. We will aim for a later start to see how well False Bay fares during Saturday’s onslaught. If we decide to launch the boat it will be from the Simon’s Town Jetty at 9.30 and 12.00 and the most likely sites will be Photographer’s Reef and Roman Rock.
If the conditions aren’t boat-worthy on Sunday, we’ll shore dive at Long Beach.