Newsletter: Long swim

Hi divers

Weekend dive plans

Sunday: Boat dives from False Bay Yacht Club to Roman Rock

We are out on the boat tomorrow for a False Bay crossing – a swim – from that side of False Bay to this side. I won’t be swimming. It’s for a good cause and if you want to show support visit the Mad Swimmers facebook page. I don’t expect to be done much before nightfall so we will skip Saturday and launch on Sunday.

It’s been a while since dived the Northern Pinnacle at Roman Rock so that will be the first dive, and the second will be the ledge and channel slightly south of the pinnacle.

Moon jelly at the Two Oceans Aquarium
Moon jelly at the Two Oceans Aquarium

City Nature Challenge – go go go!

It’s the iNaturalist City Nature Challenge this weekend (starting tomorrow), and there are events for citizen scientists of every persuasion – check out the iNaturalist facebook page to find an event near you.

We hope you’ll use your time underwater to record some species and log them as soon as you’re on land again, but other very cool sounding events include rock pooling with ocean rockstars George and Margo Branch on Monday late afternoon (details here), and, if Monday is tricky, there’s a tidal pool bioblitz on Saturday afternoon that promises to be a lot of fun (details here).

If this is all Greek to you, check out last week’s newsletter for some links and more detailed background info.

regards

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

Diving is addictive!

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Newsletter: Total eclipse

Hi divers

Weekend dive plans

No diving

Moon jellies
Moon jellies

We are headed to the Tankwa Karoo for some star (and moon) gazing this weekend, so I won’t be launching. Will see you all next week!

Shark Spotters app

The Shark Spotters mobile app has been nominated for an award for best use of tech by an NGO, and your help with voting would be much appreciated by the team. Go here to vote. It’s a lot of multiple choice votes but five minutes of your time would mean a lot! You can find links to download the very useful Shark Spotters app 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!

A Day on the Bay: Freedom Swim 2016

Maryna and Table Mountain
Maryna and Table Mountain

A day early in April was the date for the annual Freedom Swim, a 7.5 kilometre open ocean cold water swim from Murray’s Bay harbour on Robben Island to Big Bay near Blouberg. As we have in several previous years, we provided boat support for a swimmer.

This entails providing a straight course for the swimmer so as to minimise the distance swum, and keeping an eye on them to ensure that they don’t get too cold or show any other symptoms of hypothermia or distress. It requires communication with race control by radio, and a bit of boat and swimmer dodging in the early stages of the race when the water is thick with activity.

There was a 3.5 metre swell on the day, which made the ride out to the island a bit bumpy. As soon as we were in the shelter of the island, however, the sea was flattened as the swell diverted around the island. The water remained calm until we got quite close to shore, at which point the swell picked up. The final stretch from the rocks at Big Bay to the beach must have been very hairy for the swimmers!

Our swimmer, Maryna, swam in a wetsuit. She was part of the Lighthouse Swim relay team we supported last year. The water was relatively warm (13-16 degrees) clear at the island, and we could see kelp and quite far down into the sea. Great red streaks of water, probably an algae bloom, were filled with sea jellies (which stung Maryna, but she continued strongly). These were replaced by murky green water close to the shore, where the swell had lifted the sand particles into the water column.

It was a good day out, and always a pleasure to see Table Mountain in its majesty from the water.

Newsletter: So you think you can swim

Hi divers

Weekend dive plans

Saturday & Sunday: Boat or shore dives on both days

We spent Saturday morning shadowing a swimmer doing the Freedom Swim from Robben Island to Big Bay… Around 7 kilometres in 14 degree water that at times looked like brown onion soup filled with jellyfish. The swimmers are a brave and dedicated bunch and I admire them. Our swimmer did the crossing in just over two hours, but some of the swimsuit folks spent 5 hours in the water, bravely swimming into a humping current.

Swimming across Table Bay
Swimming across Table Bay

Dive conditions

The forecast looks like a piece of cake for the weekend… Light winds, not much swell and warm sunny skies. False Bay, however, looks a little off, colour-wise, and there are large colour fronts scattered across much of the bay. There is no certainty on where they will go with the light winds over the next couple of days so it is going to be a matter of making the “call to action” early each morning.

I have both shore dive and boat dive students ready to go, so will do either shore or boat based on what it looks like when we wake up, early, on both Saturday and Sunday.

Text, Whatsapp, email or carrier pigeon you desires for the weekend and I will add you to the early morning wake up call list…

Photo exhibition

If ever you had the urge to show a friend the beauty of the underwater world that you enjoy, now is your chance. Haul them off to the Two Oceans Aquarium and show them some of the stunning creatures captured on camera at a wide range of dive sites scattered along Cape Town’s shores. The photo exhibition runs for two months and is included in your entry fee to the aquarium. Read more about it 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: The Atlantic on jellyfish locomotion

Cross-disciplinary co-operation in the sciences can lead to striking results (it occurred beautifully between mathematics and computer science late last year). In this instance, The Atlantic covers a breakthrough in our understanding of jellyfish locomotion, made by a mechanical engineer.

Moon jelly
Moon jelly

John Dabiri and his team injected dye into the water around a moon jelly as it swam. Like Gandalf’s smoke rings, the jellies created rings of water behind them, moving down their tentacles as they swam.

The team later showed that the moon jellyfish actually produces two vortex rings for every beat of its bell. While the first one travels backwards, a second one rolls back into the bell itself, speeding up as it goes, and sucking water into the center of the jellyfish. This allows the animal to recapture some of the energy it spends on each swimming “stroke,” and pick up speed even when it’s making no effort. For that reason, the moon jellyfish is the most efficient swimmer in the ocean.

Read the full article here – highly recommended.

Compass sea jellies in False Bay

Compass sea jelly, photo by Jerrel
Compass sea jelly, photo by Jerrel

On one of the relatively few days this past winter (early in August) when we had really good visibility, the western side of False Bay was full of compass sea jellies. I filmed some of them from the boat while Jerrel and Nick completed their dive. Watch out for the “shark” at the end!

Bookshelf: The Unnatural History of the Sea

The Unnatural History of the Sea – Callum Roberts

The Unnatural History of the Sea
The Unnatural History of the Sea

Conservation biologist Callum Roberts has spent years researching the history of the last 1,000 years’ exploitation of the sea by human beings. The result, The Unnatural History of the Sea, is a stunning and detailed illumination of the scale of destruction we have wrought on our oceans. I had been under the impression that the development of industrial-scale fishing capabilities (factory ships, flash freezing, gill nets and the like) in the mid 20th century was what prompted the most egregious overfishing practices. This, however, is an example of baseline creep, in which successive generations look back at the conditions of nature experienced by the previous generation, and mistake them for pristine.

Humans have been harvesting marine life for over 1,000 years, moving from the freshwater ecosystems of Europe’s rivers and lakes after denuding them of all significant fish life through astonishingly aggressive (and familiar-sounding) fishing practices such as stringing nets across the entire width of rivers when fish returned to spawn. Siltation of the rivers caused by deforestation on their banks, and the development of better fishing equipment, also contributed to the move to marine fishing.

Millions of sea turtles and whales used to roam the oceans. To put that in perspective, there are under 15,000 southern right whales alive today (we think they’re recovering well – haha), and approximately 200,000 breeding green sea turtles. Numerous sea turtle rookeries, where the animals return year after year to lay eggs, are now lost to memory, after their breeding populations were completely wiped out during the 16th and 17th century by explorers and settlers in the New World. Entire seal and otter populations were hunted to extinction for their pelts. Hunters and fishermen often took far more than they needed, killing for amusement, squandering the abundance and leaving carcasses to rot or tossing excess fish – already dead – back overboard. After perusing logbooks, letters, diaries and other documents, Roberts remarks that rarely did the explorers, settlers and merchants remark on any aspect of the natural beauty of the creatures they saw on their travels, and if they did it is immediately followed by instructions on how to kill and prepare the animal, and what it tastes like.

Natural marine spectacles such as the sardine run off the Eastern Cape coast of South Africa were once far less remarkable and unusual than we find them today. The migration of herring from the Arctic down to the latitudes of the United Kingdom between May and October each year drew thousands of basking sharks (now we get a news article when four are seen in one day) and other predators, and their spawning left eggs lying on the sea floor in layers up to two metres thick. Roberts says that great white sharks also feasted on this bounty of fish, and mentions that there are too many detailed reports of white sharks up to nine metres long from the 18th and 19th century to discount all of them as false. (The maximum recorded length of a white shark in modern times is approximately six metres.) Today white sharks are seen so rarely in European waters as to create a great fanfare when one of them is spotted.

The point is that the oceans used to support far, far more life and abundance than we are able to conceive of today. Herring used to be so abundant in the seas around Scandinavia that they held up shipping. Pods of dolphins didn’t number in the thousands; they numbered in the hundreds of thousands. Whales were seen in similar numbers, surrounding boats, rubbing against them, and drenching them with spray from their blowholes. Ships navigated towards land by following the sound of countless sea turtles swimming towards the beaches they laid their eggs on.

This is a crushing, shocking book. While reading it I frequently felt myself assailed with despair and regret at how long the over-exploitation of marine resources has been underway, and how much we have lost. Bottom trawling dates back to the 14th century, and already then there were complaints (to Edward III of England, in 1376) about its indiscriminate destructiveness. Scientists visiting newly-discovered (they think) sea mounts have found their once thriving slopes reduced to fields of rubble, littered with discarded trawl nets and other fishing gear debris.

The sections on fishing in the deep sea and on trawling are devastating. Roberts contends that there is no such thing as a sustainable deep sea fishery, as the target species are so long-lived and slow growing (and unknown to science), with unknown population sizes, that there is no sustainable number of fish that can be removed without risking the species’s ability to survive.

Finally, Roberts offers some solutions to arrest the awful, seemingly inevitable slide towards ocean barrens populated only with sea jellies and urchins. The steps Roberts outlines in order to save and recover the world’s fisheries are simple to state, but will be challenging to implement:

  1. reduce present fishing capacity (i.e. number of boats, level of sophistication – this is not referring to reducing quotas)
  2. eliminate risk-prone decision making (i.e. use science, and act only when you have the facts – don’t use hope or gut feel as a decision making tool)
  3. eliminate catch quotas and instead implement controls on the amount of fishing (i.e. how much effort can be expended)
  4. require people to keep what they catch
  5. require fishers to use gear modified to reduce bycatch
  6. ban or restrict the most damaging catching methods (e.g. trawl fishing)
  7. implement extensive networks of marine reserves that are off limits to fishing

He advocates the use of Marine Protected Areas (MPAs) – scientists estimate that it is necessary to protect 20-40% of the world’s oceans in order to save fisheries for the future. Strangely, to someone who lives here and doesn’t think much of our collective will and ability to police MPAs, especially when fishing is allowed in many of them, South Africa is actually a world leader and has protected a larger proportion of her territorial ocean than many other countries (the world total is about 1.2% of the oceans, with only 0.01% of the world’s oceans designated “no take” zones, according to Wikipedia). The benefits however, even of poorly policed marine parks, are significant.

I am not sure I share Roberts’s optimism that the situation can be reversed or arrested – passages from this book come to me at odd moments, leaving me nauseated at the greed, waste and ignorance that we have displayed as a species, against the life of the sea.

There’s an interview with Roberts that I found interesting, and reviews at American Scientist and the Washington Post.

You can get a copy of the book here or here, otherwise here if you’re in South Africa.

Movie: Sphere

Sphere
Sphere

Sphere is a B grade horror/psychological thriller from the late nineties. I remember borrowing the Michael Crichton novel that it is based on from the library as a teenager, and being terrified by it. The book had a cool pale green green cover with a silver sphere on it, and a nice font – I recall these factors influencing my decision to read it at the time.

The mostly excellent main cast play scientists sent to investigate a large, spherical object that the US Navy has discovered lying on the ocean floor, encrusted with 300 years’ worth of coral (deep water coral, one assumes). Samuel L. Jackson plays a mathematician, which makes me happy. The scientists install themselves in an underwater habitat close to the sphere, and try to figure out what the spherical object is. The answer is surprising and, when the scientists think about it, not promising for their future health and happiness. The conclusion of the film is quite intellectually satisfying, if not spectacular.

This isn’t really a horror movie, although it does have a bit of gore and a lot of tension. The wisdom of middle age gave added perspective when Tony and I watched this a few months ago (I forgot to publish this post). At times I was forced to grab Tony’s arm with sweaty palms, but as many times I was able to chortle quietly as a mysterious underwater creatures (squid! jellyfish! sea snakes!) menaced various members of the crew of the underwater habitat. As in Sharknado, it wasn’t hard to see who was going to be eliminated next.

Shakespeare it isn’t. Grab your bowl of popcorn and leave your skepticism at the front door.

Get the DVD here if you’re in South Africa, otherwise click here.

Bookshelf: The Extreme Life of the Sea

The Extreme Life of the Sea – Stephen R. Palumbi & Anthony R. Palumbi

The Extreme Life of the Sea
The Extreme Life of the Sea

Father and son team Stephen and Anthony Palumbi tackle the ocean superlatives in this entertaining, easy to read volume. The Extreme Life of the Sea is riddled with pop culture references (many of which whizzed right over my head), but in between these the Palumbis conduct a tour of the most notable parts of the ocean food web. They pause at the creatures that are smallest, largest, oldest, most tolerant of heat and cold, fastest, strangest, first to evolve, and least changed since the dawn of time. The pace is rapid, but despite this the authors manage to be both interesting and detailed where necessary.

There is a recurring element of storytelling as the Palumbis introduce new creatures (they cover approximately 200 species in just over 200 pages), and I can imagine a relatively young reader with a scientific bent deriving great enjoyment from these interludes as well as from the rapid fire facts that follow each lyrical species introduction. Albatross, whales, sea jellies, worms, and giant squid line up one after the other, demonstrating their particular adaptations to the environment in which they live. Billions of microbes and viruses duke it out beyond the range of human vision. I was dazzled by how different all marine life is from humans, and how ridiculously varied.

The final chapter treats “future extremes” – the extremes we will be left with as global warming and our current fishing practices run their course. As the authors point out in concluding this chapter,

… over the long term the oceans don’t need saving. People need saving. people will need to live through the next hundreds or thousands of years when the oceans are no longer the pantry of the world, no longer safe to swim in or sail across, toxic and wracked by ever-stronger storms… The fate of the oceans has become our fate too, and we are out of easy ways to ensure that the future of the ocean is secure.

Reviews at the Washington PostThe IndependentThe Guardian, and Scientific American, if you crave more.

You can get a copy here or here. If you’re in South Africa, here.

Comb jelly on the brunswick

Ocyropsis maculata immaculata under the boat
Ocyropsis maculata immaculata under the boat

We did a beautiful May dive on the Brunswick in crystal clear, cold water, and upon rolling off the boat were greeted immediately with a fairly large group of highly structured jelly like animals, pulsing along as if on a mission to somewhere. They were hard to photograph (my best effort is above) so I took a short video of one of them.

The JellyWatch facebook page helped with identification – they do not appear in any of the marine ID books we own. This species is probably Ocyropsis maculata immaculata, a type of comb jelly that is widely and quite abundantly distributed (although WoRMS doesn’t show it as occuring off the Cape). Apparently (says wikipedia) they use their lobes to escape from danger, clapping them together in order to create a water jet that propels them backwards. They are open ocean animals, which suggests that the lovely clean water we were enjoying right at the north western end of False Bay had been brought in by an upwelling from the deep sea outside the bay, driven by the north westerly winds we’d been having.

They are ctenophores, and instead of stinging cells they have sticky cells called colloblasts that they use to catch food. Every website I’ve looked at mentions what “voracious predators” they are! Other ctenophores that we see locally are comb jellies and sea gooseberries. (More pictures of comb jellies around the Cape Peninsula can be seen here, here and here.) All of these species have little disco lights running along their bodies; this is in fact light being refracted off their eight rows of cilia, which are used for locomotion.