The tree in our driveway has a tiny green bud containing a new leaf. Despite the cold this week, I declare spring.
False Bay is quite surgy after some large swell this week, but I hope it’ll have settled down enough by Sunday for some reasonable diving. I’ll only make the call on Saturday afternoon; please let me know if you’d like to be notified of any developing plans.
Table Mountain from Rietvlei Nature Reserve
Beach cleanups
There are at least two happening this weekend:
The regular new moon beach cleanup at Surfers Corner, Muizenberg beach, organised by The Beach Co-Op (info on facebook) on Saturday at 9am
There’s a fascinating update this week from Shark Spotters on False Bay’s white sharks (spoiler: they’re awol but we’re not quite certain why yet) – read more here.
The Seabird’s Cry: The Lives and Loves of Puffins, Gannets and Other Ocean Voyagers – Adam Nicolson
The Seabird’s Cry
This is such a wonderful book that I read it twice within the span of six months. In between my two readings, during the northern hemisphere spring, Tony and I visited Pembrokeshire in Wales. This is not the home of Mr Darcy, but rather the location of several islands on which seabirds breed. Seeing puffins, gannets and shearwaters in all their glorious breeding plumage animated Nicolson’s descriptions of their precarious lives. (I do plan to share some photos and details of that visit in future posts.)
Early in this book, Nicolson points out that seabirds are the only creatures on earth that are at home in the water, on land, and in the air. To most of us, albatross are perhaps the most familiar pelagic seabirds – Carl Safina’s Eye of the Albatross both introduced and immortalised these extraordinary ocean wanderers for a popular audience. Nicolson devotes a chapter to each of ten species of seabird, including albatross, and writes with such extraordinary lyricism that at at times it’s possible to mistake this book for something other than popular science.
This blurring of boundaries is quite intentional, and completely revelatory. Rather than sounding pretentious or foolish, as most of us would if we tried to channel Seamus Heaney while summarising scientific papers and interviewing researchers, Nicolson achieves a remarkable feat of science communication. He speaks of the wonder that comes not from ignorance, but from knowledge and understanding, and how powerful a thing it is to know the facts of these animals’ lives.
If the idea of trying to join the worlds of science and poetry (or literature, or culture) grabs you, you may enjoy this video of a conversation on the subject between Adam Nicolson and Tim Birkenhead, a professor of ornithology.
Seabirds are in trouble worldwide, more threatened than any other group of birds. They are facing – amongst others – challenges wrought by changing ecosystems as the climate warms and industrial fishing robs them of their prey. To help them, we need to act, and action comes after seeing and understanding. In this book Nicolson makes an appeal to a part of us other than the rational, fact-collecting, logical entity, and asks us to empathise with these strikingly “other” creatures. I urge you to read this book.
Why so quiet? What have we been doing? Working, mostly. Trying to stay alive. And a bit of reading, and some beachcombing. Enter this is marvellous little book from fish fundi Rudy van der Elst (A Field Guide to the Common Sea Fishes of South Africa).
Chapter by chapter, van der Elst describes the types of debris that one might find on a beach. After a brief orientation chapter covering the ocean current regime around South Africa, relevant regulations, safety, beach ecology, tides, pollution and more, we launch into a tour of washed-up treasures.
Predictably, many of the items to be found are organic in nature – plants, invertebrates of various types, eggs and egg cases, fishes, birds, and shells. There are also items such as oceanographic devices, tags from marine animals, fishing equipment, cyalumes, buoys – some of these (such as tags) should be returned to their owners, and others should be removed from the vicinity of the ocean (such as discarded fishing nets and lines).
The chapter on marine animals (resting, nesting and stranded) is exceptionally useful and it is almost for this alone that I’d like to put a copy of this book in every home in every coastal town in the country. Seals, whales, turtles and seabirds can end up on the beach, sometimes in difficulty and at other times not. It can be hard to tell, and well-meaning members of the public can unwittingly cause great harm while trying to assist. A list of useful contacts in this regard appears at the end of the book, such as the Two Oceans Aquarium and the SPCA (region-specific).
The final two chapters cover miscellaneous “treasures” such as fossilised sharks teeth, sea glass, logs, and actual treasure, as well as beachcombing through the ages in South Africa. Here we learn about tidal fish traps, coastal caves, and other historical coastal dwellers who made their living from the sea.
We’ve found some awesome things on the beach, from shipwrecks to goose barnacles to rare crabs. Beachcombing is an accessible hobby that requires nothing but time, observation skills, curiosity, and a beach to stroll on.
This is a beautifully illustrated, comprehensive little volume that deserves to come with you on your beach holiday. It’ll prompt more careful examination of the flotsam and jetsam on your local beach, and, probably, more early morning low-tide visits to find the best pickings!
Seaweed Chronicles: A World at the Water’s Edge – Susan Hand Shetterly
Seaweed Chronicles
This is one of the best kinds of popular science book. It reads so easily that by the time you’ve absorbed enough material to attain a diploma in phycology (the study of seaweed), you also feel as though you’ve met and befriended a varied cast of individuals whose lives revolve – in various ways – around slippery marine algae.
It’s written by an American author, and the book centres squarely on the coast of Maine in the United States, obviously much loved by the author. It’s not clear initially that the geographical focus of the book is so narrow; some readers may want to know this in advance. While reading, I was grateful for the perspective that a Veld and Sea seaweed foraging course gave me on our local seaweeds.
Vignettes of seaweed-centred lives, from foragers turned businesspeople, to scientists, to shepherds whose flocks feast on seaweed during their coastal sojourns, introduce us to a cast of characters illustrating the many uses and commercial possibilities of seaweed, as well as the management and conservation challenges associated with its harvest. Seaweeds are pivotal in coastal ecosystems, providing vital habitat and sustenance. This isn’t just a science book (which some may find frustrating). It’s as much about the people as about the seaweed – but you will learn some science from it!
There’s a good review here at the New York Journal of Books.
Get the book here if you’re in South Africa, otherwise here.
The weather forecast predicts that we are soon to be lashed with 50 km/h winds, a 7 metre swell, and no small amount of rain. It seldom is as bad as the forecasts claim, however the swell size and direction will hammer False Bay. Despite Sunday’s weather looking peachy, I don’t think the ocean will be, so we will plan for a dry weekend… It is winter after all.
Shark Spotting at Fish Hoek beach
Shark Spotters supporters program
We are proud to announce that we have signed on as official supporters of Shark Spotters. We are Silver partners, and for larger businesses there are higher levels of support on offer. (We are hoping to encourage some of the other dive centres to consider supporting Shark Spotters, too…) Individuals can also sign on to the supporters program, or donate in many different ways.
We’ll write a blog post with more information soon – but in the mean time, we’re very happy to be contributing to the important work of Shark Spotters. If you’d like to as well, visit their website to find out how to lend your support, or drop me an email and I’ll connect you with the right people.
Last week we met Smith’s swimming crab (Charybdis smithii), a rare visitor from the tropics that arrived in the southern reaches of False Bay during the third week of January 2019. We found some adult individuals at Long Beach, well inside False Bay, on 3 March.
Juvenile Smith’s swimming crabs at Kommetjie
At the same time that fishermen were reporting adult Smith’s swimming crab off Cape Point, a huge number of tiny red crabs washed up on Long Beach, Kommetjie. There were great piles of them, but we only managed to visit a day or two later on Friday 18 January.
Juvenile Smith’s swimming crab at Kommetjie
We had to hunt a little, but after a while we found the crabs – now only a few remaining, but most of them very active and vital. Opinion from George Branch is that these are most likely the final larval stage of Smith’s swimming crab, and the same warm conditions wit anomalous westerlies that brought their adults to the peninsula, brought the juveniles.
Juvenile Smith’s swimming crab at Kommetjie
This conversation (facebook group, may be closed) suggests that the juvenile Smith’s swimming crabs were also seen on Milnerton Beach around the same time as they appeared on the beach at Kommetjie.
I took a couple of short videos of the tiny crabs, which show them in motion on the wet sand.
Apologies for the loud wave noise and less than perfectly steady camera work. Read more about these pelagic crabs, exceptionally infrequent visitors to our shores, in this post.
One of the things I love about False Bay, and about Long Beach in particular, is the tendency for creatures from all over South Africa’s coastline to end up here, often tropical marine life that got caught in the warm Agulhas current, and then within the circulation of False Bay, ending up just behind the Simons Town harbour wall.
Smith’s swimming crab (Charybdis smithii)
Thus it was, early in March, that we discovered several adult specimens of Smith’s swimming crab (Charybdis smithii) at Long Beach when we went for a dive. One or two were already dead, and the rest were struggling either on the sand, or in the shallows, looking unhealthy. The water temperature at the time was about 17 degrees.
The first hint that this unusual and rarely-seen visitor had arrived on our shores was a series of social media posts, from January, in one or two of the fishing groups I follow on facebook. (These are excellent places to keep tabs on what’s happening in parts of the ocean I might not routinely visit, and there’s a wealth of knowledge and experience among the members.) Here’s a conversation between local fishermen about seeing large numbers of adult Smith’s swimming crabs just off Cape Point (also facebook). You can also see some photos of one of the crabs from Sea-Changehere (facebook), taken on 22 January in False Bay.
Smith’s swimming crab (Charybdis smithii)
At the same time as these social media posts, there was an influx of small, red crabs on the other side of the Cape Peninsula, at Long Beach in Kommetjie. (But more on that in another post.) Two Oceans says that Smith’s swimming crabs were first described in False Bay in 1838, and then again in 1978, 1983, and 1993. This facebook thread suggests that they may have been last seen off Muizenberg around 2005-2006.
Smith’s swimming crab (Charybdis smithii)
I read more about Smith’s swimming crab in two papers: this one (Romanov et al), from 2009, and this one (Van Couwelaar et al) from 1997. The more recent paper updates many of the findings of the earlier one. Both teams of scientists behind these papers used trawl data from pelagic cruises to learn about the distribution and life history of these crabs.
Smith’s swimming crab is a pelagic crab that spends the vast majority of its one year, monsoon-driven life cycle in the water column. They are endemic to the western Indian ocean, and are usually found in the area bounded by the Arabian sea (which is west of India) and the latitude of Dar Es Salaam in Tanzania (about 7 degrees south of the equator), and from the east African coast, across east to the Maldives. They may congregate in huge patches, larger than tens of square kilometres, and may reach a biomass of more than 130 kilograms per square kilometre. These swarms are densest between June and September. During July, their concentration can peak at more than 15,000 individuals per square kilometre.
Smith’s swimming crab (Charybdis smithii)
The crabs congregate on the seafloor of the continental shelf during the months of September to December, mating late in the year. No adult crabs are usually seen between April and June (Van Couwelaar et al speculate that the adults die after breeding), at which time, after metamorphosis, the swarms again become apparent in the western Indian ocean. The crabs grow to about 7.5 centimetres carapace width.
The crabs seem to perform a diel migration, moving deeper in the water column during the day (down to 350 metres’ depth), and returning to the surface at night. They swim continuously and are voracious predators in order to support the high metabolic demand created by this constant activity. They are able to regenerate all their limbs except for their swimming legs (Van Couwelaar et al deduced this in much the same way as Abraham Wald decided which parts of World War II bombers to reinforce – no crabs with partially grown swimming legs were caught in their trawls).
These crabs are important prey for yellowtail, as for other pelagic fish species such as blue sharks, yellowfin tuna and bigeye tuna. The fishermen of False Bay observed that they made excellent bait.
Smith’s swimming crab (Charybdis smithii)
So what brings Smith’s swimming crab this far south? False Bay is way out of their range. This paper (Chapman, 1988) suggests that prior arrivals of these crabs on our shores have co-incided with weaker than usual summer south easterly winds (which has definitely been a feature of late 2018 and the start of 2019 – we had a gloriously wind-still summer for the most part) and the westward movement of warm water containing the crabs. We did have a spell of unusual westerly wind just prior to these crabs’ arrival.
A fascinating 1984 paper by George Branch describes a temperature anomaly during the summer of 1982-83. This particular Cape summer was characterised by very little of the typical south easterly winds, leading to reduced upwelling, and relatively high sea temperatures (Duffy et al, Effects of the 1982-3 Warm Water Event on the Breeding of South African Seabirds, 1984). The exceptionally warm water on the south and west coasts of South Africa caused mass strandings of some tropical animals (such as portuguese man ‘o war), mortalities of others (such as black mussels), changes in abundance of some species, and extensions of some species’ geographic range. For example, an exceptional number of juvenile turtles washed up on the beaches of False Bay, several months before the usual start of the usual turtle stranding season (which is, very loosely speaking, March-July). Prof Branch records that large numbers of healthy, adult Smith’s swimming crab washed up at Cape Hangklip, and smaller numbers at Boulders Beach, Strand, Milnerton and Blouberg. About 62% of the crabs were female, and many of them survived in aquaria for some time after stranding.
In short, it seems that we had our own little temperature anomlay, however brief, in early 2019, and the pulse of warm water brought with it these rarely seen (in Cape Town) crabs. What luck to spot this unusual visitor!
There are some lovely pictures of Smith’s swimming crab, healthy and in mid water, taken off Tanzania, here.
Eye of the Shoal: A Fishwatcher’s Guide to Life, the Ocean and Everything – Helen Scales
Eye of the Shoal
This is an absolutely wonderful book about fish. Everything about fish. Helen Scales is a marine biologist and the accomplished author of marine-themed books (I previously wrote about Poseidon’s Steed, her book about seahorses).
Here, Scales delves into the world of an animal whose variety seems almost without limit. Her book overflows with wonders, and interweaves science, adventure and mythology to shed light on the under-appreciated inhabitants of the underwater realm.
Unsolicited (this is almost always the case), I read half of this book to Tony while I was busy with it, and it delighted both of us. We learned about bioluminescent fish, poisonous fish, the sounds fish make, and the colours of their skin. We learned about fish that use tools, fish cognition, and about the state of the science regarding whether fish experience pain. We even learned about moray eels and grouper hunting co-operatively.
As a scuba diver, Scales relates tales of dives on which she observed the behaviours and phenomena she describes, and I was inspired to pay more attention to the activities of the fish we see on dives around Cape Town. They may (almost) all be the same colour, but there are certainly things that they do, and fascinating ways of being, that I am failing to appreciate.
Scales provides a bibliography on her website with links to the open access scientific papers that she used to research the book.
Get the book here (South Africa), here (US) or here (UK).
Sea Change: Primal Joy and the Art of Underwater Tracking – Craig Foster & Ross Frylinck
Sea Change
The Sea Change project may be familiar to you from their large format photographic displays, one of which was for a time along the promenade in Sea Point, and is currently in Lamberts Bay. You may have read about the project, or seen its members – ocean-loving filmmakers, journalists, scientists – diving in the cold water of False Bay year round, without wetsuits. You may even have seen the BBC’s Blue Planet II series, in which the filmmakers, guided by Craig Foster and his fellows, captured an incredible octopus sequence filmed on our doorstep in False Bay.
The Sea-Change book has been a long time in the making, and is the product of hours upon hours upon hours spent in the water, observing the animals that call the kelp forests home. The book contains a story of loss and discovery – that of Ross Frylinck – interwoven with large-format photographs of scenes from the kelp forest, taken by filmmaker and naturalist Craig Foster, a co-founder of the Sea-Change project. Foster also provides the captions.
As a diver, it was immediately clear to me that a great deal of patience and close observation was required to gain the deep understanding that Foster has of the smallest creatures living among the kelp. There is no substitute for time in the water. There is no substitute for swimming slowly, deliberately, and for spending extended time looking at one place. The marks that animals leave on rocks, kelp stipes, the sand, and even on each other’s shells, can tell a story.
I learned a huge amount about animal behaviour from this book, and about the interconnectedness of all the elements of the watery, beautiful world around the Cape Peninsula. The photographs are beautiful and striking, capturing moments that one would be extremely lucky to see during the normal course of things. Diving for more than an hour a day, every day of the year, however, makes such things more commonplace.
Sea Change presents a beautiful opportunity for the wider community of ocean lovers to learn from the unique approach taken by the Sea-Change team (this article gives a good sense of it), and to learn how to understand and observe the animals that surround us when we look beneath the surface of the inshore kelp forests. The project also has something to say about how science happens, and the vital connection between science and storytelling. Identifying animals is fun, but – as any veteran twitcher will tell you – the next level is understanding behaviour. This is a challenge I’m happy to take up.
Get a copy here, or directly from the Sea Change team.
The proportion of the world’s oceans that are fished has recently been the subject of two papers in Science, both of which used the same data set to reach different conclusions. One study concluded that 55% of the ocean is affected by fishing, while a follow up (using the original data set, but at finer resolution) concluded that the number is closer to 4%.
A janbruin emerges from a school of fish at Atlantis
Ed Yong of The Atlantic sets out the disagreement, and explains the subtleties and the points of view on each side of the debate. Far from being an insoluble scientific crisis, the divergent findings show the iterative nature of the scientific process and the manner in which back and forth between scientists leads to progress. It brings to light important questions worth considering, ones that are more important than simply asking the original question of how much of the ocean is fished.
Instead, you have to ask different and more refined questions. How much of that fishing is sustainable? Which species are being targeted? How are they faring? Can they bounce back?
