A long period 3 metre swell arrives tomorrow, drops on Saturday and then builds again on Sunday. I am planning two launches early on Saturday morning as I have several students to certify. We will meet in the car park at False Bay Yacht Club at 8.00 am. Destination unknown and weather dependent. If you’re keen on a magical mystery tour, drop me an email, text or Whatsapp.
Maritime archaeologist John Gribble is speaking at the auditorium of the South African Astronomical Observatory on Wednesday 17 August, 4.30 for 5.00 pm. His talk is entitled “From Shipwrecks to Hand Axes: An Introduction to South Africa’s Maritime and Underwater Cultural Heritage” and is described as follows:
South Africa’s maritime and underwater cultural heritage is surprisingly diverse and extremely rich. Although shipwrecks are the most obvious elements of this rich heritage resource, there are a range of pre-colonial maritime heritage resources that are less well known. This talk will introduce South Africa’s maritime and underwater cultural heritage, highlight the archaeological importance of this resource, and touch on a few examples of interesting, local historical wrecks.
There is no need to book, the event is free to the public.
I’ve been out several times this week and we’ve found clean, green and brown water in False Bay during this week’s dives. We’ll do double tank dives on both days of the weekend, starting early. I haven’t picked sites for the weekend as we will go looking for clean water when we launch. If you want to be on board, you know what to do.
Things to do
A Pint of Science is a series of evening science talks from Monday to Wednesday next week, combined with the exciting prospect, for enthusiasts, of beer. The talks will be held at the Empire Cafe in Muizenberg and Sgt Pepper in Long Street. Tickets are R35. Visit the website and see if anything takes your fancy.
As a fourth and final (perhaps) installment to our guide to ocean-related MOOCs for the curious armchair scholar, here is a list of offerings from provider edX, including one about SHARKS. All about sharks!
I have only just discovered edX, so (unlike Coursera, Future Learn and Open2Study) I have not done any of these courses, and don’t speak from experience. The format looks similar to Coursera, so you can pay to get a “verified certificate” for the course, or just choose to audit it (like a Scientologist… bad joke, sorry), which doesn’t cost anything. Like Coursera, edX has an app so you can work (on certain mobile-friendly courses) on your iPad or Android tablet.
Two courses that are focused more specifically on climate and related science are:
Climate Change: The Sciencefrom the University of British Columbia in Canada doesn’t have any current or future sessions scheduled, but you can still view the course material. This course not only covers climate, science, but aims to equip you to evaluate climate science, and to communicate facts about the climate to others.
Let me continue to encourage you to use your spare time to pursue the subjects and ideas that interest you even if you have spectacularly missed your calling in life. It is a great time to be alive! I have heard about this thing called the Internet, that apparently contains almost all of human knowledge. Including a bunch of MOOCs.
Among the first MOOCs I did were these two from Open2Study, an Australian course provider.
The final MOOC I want to mention is one I haven’t done, but Georgina and Kate have (and found it fascinating – I trust their judgment). The United Nations Environment Program (UNEP) has launched a MOOC on marine debris. You can find more information about it here. The MOOC ran until December 2015, but one hopes it will be repeated!
Coursera is not the only provider of MOOCs. In fact, providers are legion. Future Learn is another provider, owned by the Open University, with an emphasis on European (mostly British) institutions as course providers. I have enjoyed a couple of their courses and can see a few more that interest me!
Don’t use these courses as a cudgel to beat yourself with. If you sign up for one and circumstances intrude and prevent you from finishing it within the allotted time, don’t be alarmed. The learning is meant to be for your own enjoyment, and the material will either remain accessible to you as a past student, or you can re-enroll for a future iteration of the course.
MOOC stands for Massive Online Open Course. These courses are available over the internet, allowing theoretically unlimited class sizes. Courses typically comprises a mix of short video lectures, supplemental reading material, assignments and/or quizzes. Many MOOCs are offered free of charge.
Coursera is one of the largest providers of MOOCs, offering top quality classes from a range of universities, including many excellent ones. Through Coursera I have learned about chicken husbandry, animal behaviour, R programming, maps and map making, statistics, machine learning and some marine-related topics. Here is a selection of Coursera offerings that you might enjoy if you are interested in the ocean and, more broadly, the environment:
Marine Megafauna from Duke University is about large ocean creatures – turtles, whales, sharks, seals, penguins – and what they reveal about the ocean. As part of the course we read scientific papers and extracted data and conclusions from them. This is an excellent skill to learn.
Ocean Solutions from the University of Western Australia is concerned with the resources of the ocean and how we can use them to mitigate water and food scarcity, cope with climate change, and use them to source sustainable energy.
Introduction to the Arctic: Climate from the University of Alberta is the first of a planned series of MOOCs about the Arctic. It deals with the various environments that make up the Arctic, how climate systems operate there, and the impacts of climate change on this sensitive region. If you do this one, I suggest playing the lecture videos at 1.5x speed to preserve sanity.
Some of these courses have set start dates; you can either enroll and wait for the date to roll around, or, if the next starting date is undetermined, sign up to be notified when it is announced. Other courses are self-paced, so you can sign up whenever you want to and work at your own pace. Coursera has a fantastic app that functions extremely well (at least on my iPad) for learning on the go.
Coursera is not the only provider of MOOCs – I’ll share some others in a later post.
The first, hosted by the staff of the Two Oceans Aquarium, was about safe and ethical handling protocols for sharks and rays. Scientists apply tags, take samples and measure animals in order to learn about them, and some contact is inevitable. It is vital to do all the work as quickly as possible, and with as little stress to the animal as possible. I didn’t attend this workshop, but comments from participants indicated that it was extremely useful and practical, with a hands-on section conducted outdoors.
The second workshop, hosted by the team from the Save Our Seas Shark Education Centre in Kalk Bay, was about science communication, which is dear to my heart. I tweeted quite a lot of detail from this workshop (keep reading…), and it was fantastically useful.
The final workshop was hosted by the Save Our Seas Foundation and its CEO Michael Scholl (also known as “the drone guy”!), and dealt with automated identification of sharks from the shape of their dorsal fins – FinPrinting! I didn’t attend this workshop either, and would be interested to hear more about it.
As for the first and second day of the symposium, I created a storify timeline that compiles tweets and images from the day. You can view it here, or read through it below.
Collaboration between scientists leads to amazing things, like the massive acoustic tracking system that covers the entire south and east coasts of South Africa.
You can tell a lot about what an animal is doing, without necessarily being right next to the animal all the time, with some clever technology and mathematics (yay maths!)
There are tiger sharks that are partially resident off Ponta do Ouro, Mozambique. They are being tracked and studied. Something to bear in mind next time you visit!
Sharks that cross borders (e.g. tiger sharks, great white sharks) are hard to conserve and face huge risks when they move out of protected areas.
False Bay’s great white sharks are incredibly well understood (great work has been done in the last 5-10 years), and at the same time the more we know, the more questions there are!
We are beginning to get a better understanding of sevengill cowsharks in False Bay and research is ongoing. Plus, did you know there’s a huge sevengill population around Robben Island?
Many of the shark and ray populations around South Africa’s talks are not comprised of separate groups of animals (e.g False Bay’s white sharks, Gansbaai’s white sharks and so on), but interbreed all along their range. This means you can’t protect one aggregation site and expect the species to survive and thrive – you have to think about threats along the entire range of the animal. This was a common theme in the genetics talks (which is a difficult subject to explain to peasants like me).
Juvenile hammerhead sharks aggregate in Mossel Bay at certain times of year! (This wasn’t the point of what was an excellent talk, but I was excited to hear it.)
Earlier this week I had the great privilege of attending the 3rd Southern African Shark and Ray Symposium, which was held from 7-9 September at the Blue Horizon Estate above Simon’s Town. I am not a shark scientist (these days I am probably best described as a lapsed mathematician) but have an interest in the subject so I went to listen. If I had to provide some bite-sized takeaways from the first day of the symposium, jotted down without applying any of the science communication principles I learned at the workshop yesterday, it would be these:
Shark mitigation – avoiding negative interactions between humans and sharks – is HARD and a lot of smart people are working on the problem.
The City of Cape Town is a world leader in shark mitigation efforts, along with Shark Spotters. They really think about the problem, and care about both people and sharks.
If you are not blessed with high coastal terrain and surface-swimming sharks (which would permit a shark spotting program like Cape Town’s one), other shark mitigation measures are in the pipeline… From orca-patterned surfboards (and wetsuits?) to shark exclusion nets to large-scale electrical repellent cables.
The KZN Sharks Board catches a lot of sharks, rays and other animals in their gill nets and drum lines, and this is upsetting and far from ideal. But they facilitate an incredible amount of scientific study, too – their catches do not go to waste.
The KZN Sharks Board is committed to finding measures other than gill nets and drum lines to keep bathers safe, and they are actively working on the problem (refer to the electrical shark repellent cable I mentioned above).
Sometimes scientific research doesn’t look the way you expect or imagine. Ruth Leeney of Protect Africa’s Sawfishes spent months on the ground interviewing Mozambican villagers in the far north of the country to assess the population status of sawfish in Mozambique. She collected data that no one else could have obtained by other means!
Smaller, less charismatic sharks, like catsharks, need more love. There are also whole families of sharks that divers don’t see (such as dogfish) and hence aren’t really aware of. They are caught prolifically as by-catch and not much is known about them. But some smart people are working on this!
There are motivated, talented scientists working hard in South African government departments to protect our marine resources and making recommendations to manage them sustainably. (There’s also many a slip ‘twixt cup and lip, but they are trying very hard.)
Technology – be it cameras, software, or tags – is enabling great leaps in our understanding of what’s out there, which will enable us to protect and conserve things better.
Ocean acidification as a result of climate change could affect sharks directly, by actually wearing away their denticles (tooth-like structures on their skin). Denticles protect sharks and help them to swim faster.
I’ve been appallingly tardy in writing about this talk, but recent events in False Bay have reminded me that my notes have been sitting waiting for me to attend to them for several (ahem) months. My diary indicates that the series of talks that it was part of was held in November 2012. Dr Barnett has in fact left South Africa and returned during the time it’s taken me to get to this task. Sorry.
Broadnose sevengill cowsharks (Notorynchus cepedianus) are part of the order Hexanchiformes, which comprises six species. This is a primitive order of modern sharks with six or seven paired gill openings (most sharks have five). Four species are cowsharks, and the others are deep water sharks.
Surprisingly little is known about sevengill cowsharks, but Dr Barnett contends that they should be an extremely important apex predator. They are found worldwide, but not (so far) in the north Atlantic. There are far more of them than there are white sharks, and they eat the same sort of things: fish, rays, seals, and other sharks. Their role in coastal ecosystems is very important.
They are found in coastal waters of countries including (but not limited to) Australia, South Africa, Argentina, and California. There are known nursery areas at the latter two locations. Only one pregnant female has been dissected. She was carrying 82 pups (for context, white sharks bear 2-10 young, hammerheads about 50, whale sharks up to 300, and most other shark species 2-40). Their reproductive cycle is thought to be about two years in length. It is not known at what age these sharks reach sexual maturity.
Sevengill cowsharks are on the IUCN Red List as data deficient (not enough is known about their conservation status). The IUCN Red List website page about the sevengill is informative. They are a target species for recreational fisheries (we often see specimens with hooks stuck in their mouths when we dive at Shark Alley), and a low value bycatch species for commercial fisheries in South Africa. There are several semi-commercial fisheries elsewhere that target them. There is some evidence that the fisheries in California and Namibia are not sustainable.
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For some time, Dr Barnett has been studying the sevengill cowshark population found in the south eastern corner of Tasmania, in the system of bays that makes up the Derwent River estuary. The water here is turbid and there is a wedge of salt water that moves up and down the river with the tide. The river is at most 40 metres deep, and Norfolk Bay is about 20 metres deep. The winter water temperature in the area is 8-13 degrees, and in summer the maximum water temperature is 21-22 degrees. Much like False Bay (except for the river)!
The estuary is a shark refuge area and also includes populations of soupfin and smoothhound sharks, which pup there. The aim of the study has been to determing the population structure, abundance, diet, habitat use, and predator-prey relationships of the cowsharks.
Barnett fished for sharks using long lines with 50 hooks per line, deploying four lines per night. He tagged and released 457 sharks in total, took biological samples and measurements, determined their sex, and flushed their stomachs to see what they’d been eating. Sixteen percent of the females had mating scars (bite marks). He found more sharks each year in summer, and fewer in winter. Do they leave? Or do they not get caught in winter? Of the 457 sharks tagged, 68 (15%) were recaptured, in the same bay as where they were first caught.
Cowsharks are about 50 centimetres at birth, and after a year they are 70-80 centimetres long. The Derwent estuary is not a pupping or nursery ground, based on the measurement distribution that Barnett observed. He caught 60-100% female sharks (depending on what time of year he fished), averaging about 60% females. In winter he found no males, with a few showing up by spring.
Barnett also set an array of 74 VR2 acoustic receivers 800 metres apart, during the period December 2007 to June 2009. He set them along the boundary of the protected area and at entrances to bays and inlets. For the movement study he tagged 43 animals (31 female) with acoustic tags that communicate with the receivers. The process to implant the tag is a three minute surgery. He found that no Norfolk Bay shark moved to the upper Derwent estuary, and no estuary shark moved to Norfolk Bay. This suggests strong site fidelity. There is some overlap between the populations in late autumn, and by winter most of the sharks (including all the males) left the area. After winter the animals returned to where they were tagged.
Pop up archival tags attached to five males and five females located the makes 1000 kilometres north in Jervis Bay, south of Sydney, and the females closer – slightly offshore, with one visiting a depth of 300 metres. The sharks are more active and in shallower water at night, spreading out more. During the day they spend a lot of time close to the seabed, moving up and down in the water column at night.
Barnett tagged several of the sevengill sharks’ prey species, and determined that the sevengills were only in the bay when their prey items could be found there. The fact that the sharks are not breeding in the area suggests that their habitat use is indeed diet related.
False Bay study (ongoing)
Excitingly, broadnose sevengill cowsharks are the subject of a current study in False Bay involving Dr Barnett and local scientists, making use of the array of acoustic receivers that was originally set to study white shark residency patterns. There are also compatible receivers in Algoa Bay, Mossel Bay, Gansbaai, Port Alfred, Port St Johns and on Aliwal Shoal. At least nine sharks have already been fitted with acoustic tags at Miller’s Point, and a hook was incidentally removed from one shark’s mouth.
Miller’s Point is a unique aggregation site: the researchers aim to determine why. Female sharks that look very pregnant are often observed by divers there. The researchers will use the data from the acoustic receivers to try to determine the sharks’ habitat use in False Bay, their seasonal movements, the population structure and the effects of fishing. This will assisst in managing the species. They will also study their interaction with white sharks (with whom they compete for food), and the cowsharks’ predator-prey interactions with other species. This is important for ecosystem management.
Sevengill sharks have been seen and caught at Robben Island in Table Bay, in Betty’s Bay, and in Gordon’s Bay (at night). It is possible to dive with the Betty’s Bay sharks, if you know where they are! It isn’t known whether there are any at Seal Island, perhaps closely sharing that habitat with the white sharks.
Dr Barnett’s results from his work in Tasmania are fascinating because they shed light on broadnose sevengill cowsharks as a species as well as their specific behaviour in the Derwent estuary. So little is known about our local population that the temptation to try to generalise some ideas from his Tasmanian research is irresistible. I hope that the tagging study currently taking place will increase our understanding of these local celebrity sharks, and that it will assist in managing the species and the places they live so as to ensure that the population continues to thrive. Yay science!