Newsletter: Copycat weather

Hi divers

Weekend dive plans

Sunday: shore or boat dives, depending where the viz is!

A cold front arrives tonight and will make itself felt until Saturday evening. Sunday will be best for diving. I have student dives to complete; if the inshore conditions are good, we’ll shore dive. If the visibility is only to be found further out, we’ll launch Seahorse. If you’re keen to get wet, let me know and I’ll update you on Saturday afternoon.

Storm clouds
Storm clouds

Keeping out of trouble

There’s lots going on as we sail into spring:

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: Cocktail weather

Hi divers

Weekend dive plans

No dives

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.

Sightings

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!)

John Dory at Long Beach in January 2010
John Dory at Long Beach in January 2010

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.

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!

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.

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!

Article: National Geographic on great white sharks

The July 2016 issue of National Geographic contains an article entitled “Why Great White Sharks are Still a Mystery to Us“, and luckily for those of us who don’t have approximately $100 to drop on a magazine (I exaggerate, and it’s probably worth it), it’s available online as well. It’s an excellent explanation for why and how technology is being used to study these remarkable creatures.

The great white shark is the ocean’s iconic fish, yet we know little about it—and much of what we think we know simply isn’t true. White sharks aren’t merciless hunters (if anything, attacks are cautious), they aren’t always loners, and they may be smarter than experts have thought. Even the 1916 Jersey Shore attacks famously mentioned in Jaws may have been perpetrated by a bull shark, not a great white.

We don’t know for sure how long they live, how many months they gestate, when they reach maturity. No one has seen great whites mate or give birth. We don’t really know how many there are or where, exactly, they spend most of their lives. Imagine that a land animal the size of a pickup truck hunted along the coasts of California, South Africa, and Australia. Scientists would know every detail of its mating habits, migrations, and behavior after observing it in zoos, research facilities, perhaps even circuses. But the rules are different underwater. Great whites appear and disappear at will, making it nearly impossible to follow them in deep water. They refuse to live behind glass—in captivity some have starved themselves or slammed their heads against walls.

The photographs are by Brian Skerry. It’s worth checking out. Read the article here, or pick up a copy of the magazine when you see it on the shelves.

And for the inveterate shark fans and those who want to pursue some further education, it’s not too late to sign up for the Shark MOOC on edX that started on 28 June. Click here to join in.

Bookshelf: Pristine Seas

Pristine Seas: Journey to the Ocean’s Last Wild Places – Enric Sala

Pristine Seas - Enric Sala
Pristine Seas – Enric Sala

Those of us who will likely never visit Kingman Reef and the Line Islands in person should be grateful for Enric Sala. Marine ecologist and National Geographic Explorer in Residence, Sala brings the same substance, urgency and gravitas to his underwater photography that Thomas Peschak does. He can truly be called a conservation photographer, having left a career as a research scientist to work on saving the ocean’s wild places.

Sala’s current project is to explore and protect the last pristine marine ecosystems on the planet, and to this end he has led expeditions to comparatively untouched locations around the world. This book documents ten of those expeditions, from tropical to Arctic waters. Rich with photographs, contextualised with beautiful National Geographic-style maps, it is a delight.

Read an interview with Sala here, and an article about the man by author Juliet Eilperin can be found here.

Get a copy here (South Africa), here or here.

If this is right up your alley, check out Blue Hope as well.