Newsletter: Winter closing in

Hi divers

Weekend dive plans

Sunday: Boat dives from Simons Town jetty at 9.30 and 12.30 (suitable for Open Water divers)

It feels very much as though winter has arrived (minus the rain), mostly in the early mornings. When daytime temperatures rise into the twenties, it’s not totally unpleasant! Sunday is one of those days, and we will launch from Simons Town jetty at 9.30 and 12.30. Both sites will be a maximum depth of 18 metres as I have a bunch of Open Water students to qualify.

Catshark egg case
Catshark egg case

Citizen shark science

We are big fans of citizen science, so it is great to hear about ELMO’s catshark reproduction study, for which they need volunteer divers. Read more, and sign up, here.

regards

Tony Lindeque
076 817 1099
www.learntodivetoday.co.za
www.learntodivetoday.co.za/blog/

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Newsletter: To the point

Hi divers

Weekend dive plans

Sunday: Boat dives from Hout Bay harbour

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.

View towards Misty Cliffs from Scarborough Beach
View towards Misty Cliffs from Scarborough Beach

Good news

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.

regards

Tony Lindeque
076 817 1099
www.learntodivetoday.co.za
www.learntodivetoday.co.za/blog/

Diving is addictive!

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Newsletter: Here today, gone tomorrow

Hi divers

Weekend dive plans

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.

False Bay this morning
False Bay this morning

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.

Great news

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!

regards

Tony Lindeque
076 817 1099
www.learntodivetoday.co.za
www.learntodivetoday.co.za/blog/

Diving is addictive!

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Sharks! MOOC videos (part II)

Here is a selection of the videos for weeks three and four of the recent Sharks! MOOC hosted on edX. You can find weeks one and two here. All the videos are available on youtube if you’re really interested – you can check out the channel containing all this year’s videos, or a giant playlist containing all the videos from the 2015 iteration of the course.

Dark shyshark on the sand at Long Beach
Dark shyshark on the sand at Long Beach

Week 3: Thinking like a Shark – Brains and Behavior

Introduction – thinking like a shark

General organisation of the nervous system

Brain regions overview

Brain size

Prey localisation

Seeing underwater

Eyes for deep water

Lateral line system and Ampullae of Lorenzini

Electric snouts

Group hunting – broadnose sevengill sharks – an interview with Dave Ebert on research he did decades ago on the sevengill cowsharks of Millers Point

Week 4: Sharks in the World – Human Interactions, Ecology, and Conservation

Introduction – sharks in the world

What sharks eat

Food webs

What eats sharks?

Deep water communities

Shark struck

The problem with shark nets

Why are aquariums important?

Husbandry

Industrial fishing

The art of Ray Troll

Sawfish DNA

Sharks! MOOC videos (part I)

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.

The course format was a mix of video lectures and interviews, notes, diagrams and multiple choice questions for grading purposes. The videos are available on youtube – you can check out the channel containing all this year’s videos, or a giant playlist containing all the videos from the 2015 iteration of the course.

I’m going to link to some of the most interesting videos below, so you can get a taster of what the course was like. Please sign up next time it gets offered, if you didn’t do so this time!

Broadnose sevengill cowshark at Shark Alley
Broadnose sevengill cowshark at Shark Alley

Week 1: The Big Shark Picture – Biodiversity and Evolution

Intro – the big shark picture

Shark tracking

Light, depth and landforms

Habitat dive

Hotspots

Origins of taxonomy

Start with the fins

Skeletal anatomy

14 living orders

Species discovery

A walk through deep time

Bear Gulch – a golden age of sharks

Megatooths of Maryland

Week 2: Miracles of Evolution – Functional Morphology and Physiology

Introduction – miracles of evolution

Why a hammerhead?

How shark tails work

Drag

Oil and water

Edged weapons

Blue shark vs white shark

Pursue or ambush?

Manta ray feeding and migration

Shark vs mammal circulation

Breathing water

Countercurrent gas exchange

Osmoregulation in the bull shark

Greenland sharks

Reproduction in the sand tiger (ragged tooth) shark

Modes of reproduction

Week 3 (shark brains and behaviour) and 4 (sharks in the world) videos will follow in a separate post.

Article: The New York Times Magazine on animal tagging

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.

A white shark with a satellite tag
A white shark with a satellite tag

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.

Erik Vance’s article on great white sharks for National Geographic covers tagging, and he elaborates on his blog about how tags can facilitate population estimates. You can also read about whale tagging, tuna tagging, and the tagging study taking place on False Bay’s cowsharks.

What a time to be alive. Read the full New York Times Magazine article here.

Two ways to count sharks

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 NothingI 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.

A dorsal fin breaks the surface
A dorsal fin breaks the surface

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.

And for some hot off the press South African research on a related subject but taking a different (genetic) approach, check out this press release. The study’s author, Sara Andreotti, spoke on the topic at the SA Shark and Ray Symposium in 2015.

Help Shark Spotters create a free beach info smartphone app!

The signs and Shark Spotters flag at Glencairn
The signs and Shark Spotters flag at Glencairn

Shark Spotters have been keeping bathers and surfers safe, and providing groundbreaking research on Cape Town’s white sharks, for over 10 years. They are currently developing a smartphone app that will provide information on sightings of sharks and other marine life, sea conditions, and other information pertinent to the Shark Spotters program.

The app will be available free of charge, but there are some development costs that have to be raised before it can be launched.

Click here to donate – every bit helps!

Newsletter: Diving 9 to 5

Hi divers

Weekend dive plans

Saturday: Shore dives at Long Beach

Sunday: Boat dives from Simon’s Town jetty at 10.00 to the wreck of the Brunswick and 12.30, site to be determined on the day

Liam and Christo near the Brunswick
Liam and Christo near the Brunswick

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.

If you want to dive, let me know!

Support Shark Spotters

Don’t forget to donate to help the Shark Spotters complete their beach info smartphone app! Also, there’s an auction and comedy evening (with Nik Rabinowitz!) at the Two Oceans Aquarium on Wednesday 27 July, also in aid of Shark Spotters’ research. There’s more information about the event here.

regards

Tony Lindeque
076 817 1099
www.learntodivetoday.co.za
www.learntodivetoday.co.za/blog/

Diving is addictive!

To subscribe to receive this newsletter by email, use the form on this page!

Newsletter: Wishing winter away

Hi divers

Weekend dive plans

Sunday: Boat dives from Simon’s Town jetty to Photographer’s Reef and Roman Rock OR shore dives at Long Beach

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.

An app for beach lovers

The Shark Spotters centre at Muizenberg
The Shark Spotters centre at Muizenberg

Shark Spotters, who do pioneering beach safety work and shark research in Cape Town, are crowdfunding a mobile app which will provide information on beach and surf conditions, shark and other marine animal sightings, and whether the Fish Hoek exclusion net is currently deployed. The app will be available free of charge. Watch this video for more information about the app, and give your support by donating here!

regards

Tony Lindeque
076 817 1099
www.learntodivetoday.co.za
www.learntodivetoday.co.za/blog/

Diving is addictive!

To subscribe to receive this newsletter by email, use the form on this page!