Rays – Learn to Dive Today Blog

You need this: the Shark Spotters smartphone app

After a successful Back a Buddy campaign, Shark Spotters launched their free shark safety smartphone app in the summer of 2016. The app has had excellent uptake by water users of all stripes, but I’d like to draw it to your attention in case you aren’t familiar with the ways in which it can make your beach life better and safer! Whether you’re a surfer, a diver, an ocean swimmer, a beach comber, or someone who looks forward to long summer days under an umbrella on the sand, the Shark Spotters app can make a difference to you.

Shark Spotters operate at eight beaches around the Cape Peninsula: four (Muizenberg, St James/Kalk Bay, Fish Hoek & Caves, Kogel Bay) year-round, and another four (Glencairn, Clovelly, Monwabisi and the Hoek, Noordhoek) from October to April, during the warmer months.

The app allows one to set a home beach – you can see from the image above that mine is Fish Hoek – and when you start the app, you’ll get information for your home beach immediately. Tapping on the home beach block at the top of the screen (where it says “Tap for more”) brings one to a series of screens that you can navigate through by swiping the bottom block on the screen.

Information on recent sightings at my home beach

The information provided is extensive. You can see information on the last three shark sightings at your home beach, the weather and sea conditions (temperature, wind direction, tides, moon phase, swell), and information on what marine life is in the area. This latter information is not a nice to have so you can look out for dolphins from shore, but an important indicator of the likelihood of a shark being in the area. Dolphins, rays and schools of fish can draw white sharks, while sunfish (and even seals) may be mistaken for a shark when viewed from a distance by an untrained observer.

There’s also information on what facilities are available at the beach, and a short video for each beach, usually taken each morning, showing the prevailing conditions.

All this information is available for all the Shark Spotters beaches, not just your home beach, and you can view a different beach by selecting it from the list that appears under your home beach on the home screen.

Digging into the app, you can find a detailed list of all the recorded shark sightings, and in the settings you can turn notifications of sightings on or off according to your preference. I have them switched on, because I like to be reminded of a world outside the office.

The further menu options, shown above, give you access to a large amount of data about the Shark Spotters program, the exclusion net at Fish Hoek beach, how the flag system works, great white sharks, and more. Most of the menu options also provide links to more detailed information online, if you want to know more.

You can download the app for iOS here, for Android here, or use the download links from the Shark Spotters website. The app is completely free of charge, but Shark Spotters is funded by the City of Cape Town, Save Our Seas Foundation, and other generous sponsors, including individuals. Shark Spotters welcomes donations. Click here to donate.

Bookshelf: Manta

Manta: Secret Life of Devil Rays – Guy Stevens & Thomas Peschak

I found this book to fill a significant gap in my manta ray knowledge, which was (to be honest) virtually nonexistent. Author Guy Stevens is founder of the Manta Trust and a Save Our Seas project leader, and has spent 15 years in the Maldives studying these enormous, charismatic elasmobranchs. The Manta Trust co-ordinates global manta research efforts, with the aim of protecting and conserving mantas and their relatives.

The photographs in this book are by Thomas Peschak, co-founder of the Manta Trust, with whose extraordinary work you should be familiar. (If not, look here, here and here.)

Everything you might want to know about mantas is here, without being glib about the fact that there is still much we do not understand about these animals. The text covers their biology, life histories, threats to their survival, an identification guide, and numerous accounts by field scientists who study mantas and devil rays. (It was hard not to be envious reading some of the day-in-the-life bits!)

This is a beautiful, substantial book. Get it here.

Farewell (for now) to the short tailed stingrays

This my the final video (for now) of short tailed stingrays (Dasyatis brevicaudata) swimming under the boat on a sunny February day in between dives.

[youtube=”https://www.youtube.com/watch?v=N1Sw21CYMAo&w=540″]

The IUCN Red List has these rays as of “least concern”, but they are protected in Western Australia because of their tourism value. There are locations in this region where tame stingrays interact with visitors; much like the rays at Struisbaai harbour.

More stingrays under the boat

We spent quite a bit of time with the short tailed stingrays (Dasyatis brevicaudata) between dives this past summer. Here’s another short video of one under the boat in shallow water.

[youtube=”https://www.youtube.com/watch?v=ERlIQJvAxvg&w=540″]

These rays can grow to over two metres in diameter and weigh a few hundred kilograms at their maximum. They are a popular target for fishermen.

Stingray in the sunshine

Here’s another view of one of the short tailed stingrays (Dasyatis brevicaudata) in the sunshine last month. Surprisingly little is known about these animals. They’ve been studied in Australia and New Zealand where they are also found, but not much work has been done to learn about them here.

[youtube=”https://www.youtube.com/watch?v=rI5h-L6Wzi0&w=540″]

If you have watched the original BBC Blue Planet series (if you haven’t, why not?) you will have seen the massive aggregations of these rays that form at the Poor Knights Islands off New Zealand. I wonder if there are any similar aggregations off the South African coast that we don’t know about?

Watching stingrays from the boat

We visited this beautiful short tailed stingray (Dasyatis brevicaudata) near Millers Point between dives one day in mid February. They’re commonly seen during the summer months, when water temperatures in False Bay are between 16 and 22 degrees celsius.

[youtube=”https://www.youtube.com/watch?v=iHz6Ar-XejQ&w=540″]

I find them to be more curious about the boat than they are when we see them during dives. Then, they’re most often resting or eating on the sand, and after a short time they swim away.

Newsletter: High hopes

Hi divers

Weekend dive plans

Saturday: Meet at the False Bay Yacht Club Parking at 9.00am for a double tank dive

The south easterlies are not ready to leave yet for the winter, but they are giving us a break right now. The forecast is for strong westerly wind tomorrow which will, if it blows, clean up False Bay rather nicely for some good visibility on Saturday. There is a 3 metre swell arriving on Saturday but I think it will be fine for a dive or two, and the tides are in our favour.

We will meet at the False Bay Yacht Club Parking at 9.00am. We’ll double tank it and choose the sites once we’re out there. Let me know if you want to be on board.

Giant short tailed stingray at Millers Point

I had a couple of good days on the boat this week, the highlight being watching this huge giant short tailed stingray on a flat calm day.

Water

We shared a blog post about diving during a drought this week. Check it out! Also, the WWF’s fourth Wednesday Water File was published yesterday, and it’s very pertinent. It’s all about toilets. Read it here.

regards

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

Diving is addictive!

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Biscuit skate on a night dive

We came across this small biscuit skate (Raja straeleni) while doing a night dive at the jetty in Simon’s Town, on the occasion of Diversnight 2017. They are found in the eastern Atlantic ocean all the way down to 700 metres depth, grow really slowly, and are frequent bycatch from hake trawling operations off the South African coastline. SASSI says don’t buy it. The species is data deficient on the IUCN Red List.

[youtube=”https://www.youtube.com/watch?v=CG2aXF-TaZg&w=540″]

These skates have thorn-like stings along part of their tails, and this one seems to have a whole lot else going on in the tail region which looks as though it would help him camouflage among seaweed. (None of the biscuit skates pictured in our fish identification books have quite such fancy tail-gear.) Also watch how he flicks sand over himself for additional disguise when he stops moving.

Also, they can jump – perhaps a little known talent… Once, while Clare was on duty at the aquarium, a small one leaped right out of the shallow ray pool that used to be next to the touch pool, and landed on the floor. It was a quiet Sunday afternoon. A quick manhandle and he was replaced in his pool (and that exhibit was moved soon after)!

Diving in the I&J Ocean Exhibit at the Two Oceans Aquarium

The I&J Ocean Exhibit is the largest tank at the Two Oceans Aquarium, and has been open since mid-2016. It features a full 10 metre long tunnel, and is home to Yoshi the turtle, two green turtles, bonito, musselcracker, a guitarfish, some rays, and several other species. Watching the animals being fed at 12pm on a Sunday is a highlight of my monthly shift at the aquarium.

I needed to dive in the tank, and Tony and I were lucky to be escorted by the wonderful Angie, who has been a Divemaster at the aquarium for several years. The dive is easy: the tank is shallow, warm, and the visibility is to all intents and purposes limitless. Angie pointed out that in an out of air situation, we’d just do a CESA to the surface. (This makes the aquarium perhaps the only location you’d use this skill in its pure form…) The animals aren’t dangerous, but they need to be respected, and the soft acrylic windows pose a particular challenge as a careless bump with some dive gear would scratch them from the inside.

The green turtles are special. Bob was found in poor shape on the beach at De Hoop when he was the size of a dinner plate, and after several months in intensive care, regurgitated a quantity of plastic, including ribbons and balloons. Now, he is friendly and very attached to humans – he especially loves to have his shell tickled, and wriggles from side to side in appreciation. As a result of the amount of time he spent in veterinary care, he will stay at the aquarium for his own safety.

Sandy was most likely struck by a boat propellor near Witsand at the mouth of the Breede river. The scars are visible on her carapace in the photo above. She was recently discovered to be definitely female (turtles are tricky). She’s not quite as interested in humans as Bob is, but she was mesmerised by her tiny reflection in Tony’s camera lens, and approached closer and closer to examine it.

In addition to the turtles, Tony enjoyed the fantastic giant guitarfish, and spent much of the dive looking for it. The rays are like puppies, full of youthful exuberance and energy. The schooling fish mostly keep out of the way of the divers, near the surface of the tank, but are a treat to be close to.

We last dived in the aquarium a couple of years ago. The kelp forest, which was an enormously enjoyable dive, is currently closed for renovations but will be re-opening soon. The new shark exhibit will also be open for dives soon (it is already open for looking at, with nine ragged tooth sharks in residence). Meanwhile, the Ocean Exhibit provides more than enough diversion on a day that doesn’t offer good enough weather for a sea dive.

Dive date: 29 April 2017

Air temperature: 30 degrees

Water temperature: 24.8 degrees

Maximum depth: 6.1 metres

Visibility: 15 metres

Dive duration: 36 minutes

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.