Early in December last year, Tony escorted some members of the media on a dive/snorkel in the shark exclusion net at Fish Hoek beach. To remind you, this net is a highly visible barrier in the ocean, designed to keep sharks and humans apart, and both species alive. It was specifically designed not to catch anything, unlike the gill nets that are deployed by the Sharks Board off the KwaZulu Natal coast. This is what the net looks like from underwater:
This is what it looks like on the surface. The day was quite grey and dreary when we dived it, but the yellow buoys along the top of the net are highly visible. At the end of the day the net is retrieved, and if the weather and sea conditions permit, it is deployed again in the morning.
Here’s the view on Scarborough beach looking north, towards Misty Cliffs (the mist is visible in the distance). There’s a little river flowing over the beach into the sea, just visible to the left of the boardwalk.
One Tuesday in early December, Tony escorted some members of the media – Murray Williams of the Cape Argus, and Bruce Hong of Cape Talk radio, on a dive along the inside of the shark exclusion net at Fish Hoek beach. It was just before the start of the school holidays, and since the net has been trialledmultiple times by now and is working well, it’s a good time to raise awareness of the additional beach safety and – importantly – peace of mind that the net offers. I tagged along as photographer.
Over-under view of the exclusion net at Fish Hoek
The net at Fish Hoek beach is a world first. It has a fine mesh that is highly visible underwater, and is designed not to catch anything – unlike the shark gill nets in KwaZulu Natal. The net is put out in the morning and retrieved at the end of the day, but only when sea conditions allow it. The south easterly wind can bring huge quantities of kelp into Fish Hoek bay which would foul the net, so when there is a strong south easter the net cannot be deployed.
If you’re a water person, please educate yourself on how the net works, and its intention, and share it with your friends. Even now, nine months after the trial started, I hear uninformed comments from people who have not bothered to do any reading about the net, and assume it’s the same kind of net as the ones in Durban. It’s not. The whole idea is that nothing – no sharks, no humans, no klipfish – gets hurt. Shark Spotters and the City of Cape Town have been very clear on this from the start. I had a bit of a rant about this late last year.
Murray dives down to check out the exclusion net
I digress. We went to the beach, got suited up, and went to check out the net. It was spring low tide, so at its southernmost end we were in about 2 metres of water. The net is high enough that when the tide comes in and the yellow floats rise with the water level, it simply unfurls further downwards, making an unbroken curtain. The lower portion of the net rests on the sand, with two parallel weighted lines to ensure that it lies flat. You can see that in the photo above Murray is gripping one of these leaded lines, and that there is a fairly large amount of net waiting on the sand for higher tides.
The divemobile ready for action
Entering the water watched by some schoolboys on an outing
Monwa, superhero
Your photographer
Batman on the surface
The net hangs down like a curtain and rests on the sand
Murray and Monwa discuss the net
We stuck close to the net, and didn’t see much marine life on the sandy bottom. I spotted a large sand shark (when I say I “spotted” him, I mean that I almost landed on top of him). We were mutually surprised, and he zipped away into the bay, sliding neatly under the bottom of the net. I also saw a box jelly cruising along the net. Given my recent history with box jellies, I kept clear! The sea floor in the area where the net is deployed is level, sandy and free from rocks. There’s more life on the catwalk side, where beautiful rock pools wait to be snorkelled.
We were accompanied by Monwabisi Sikweyiya, who is the Field Manager of Shark Spotters. He is a hero and I always feel a bit star-struck when I see him (although he has no idea why – he probably just thinks there’s something wrong with me). He swims along the net regularly – someone does each time it is deployed, actually – to make sure that it’s released properly and hanging straight down.
After the dive
Swimming inside the net is completely voluntary. When a shark is seen in Fish Hoek bay the Shark Spotter still sounds the siren and the flag is raised to clear the water. The Shark Spotters team are still waiting to see how a shark will respond to the net when it swims close enough to be aware of it. So far none of the local sharks have come close to the net, as the summer season when sharks move inshore has only just started. Tony was half hoping that we’d be swimming along inside the net, look out through the mesh – and blammo! – see a great white shark. But we had no such luck, if that is the right word.
You can read the article that Murray Williams from the Argus wrote after the dive, here.
I’d suggest you read through my write up of Dr Barnett’s talk last November. There’s a lot of background information on these beautiful animals in that post.
Cowshark with a small external tag
Why tagging studies need to be done
Here is an explanation, in relatively simple terms, of why cowsharks are tagged for scientific research. Tell your friends.
We don’t know much about sevengill cowshark behaviour and habitat use in South Africa’s waters. Actually we know almost nothing.
Because we don’t know for sure where they mate, give birth, and rest, we don’t know how best to protect them.
We can’t protect every bit of coastal water and every species of fish. Because why? Because we live in the real world, where there are extensive commercial interests, finite amounts of funding, and a lack of resources and will to police things.
We can’t go on suspicions and gut feel when deciding which areas and species to protect. This is because there are extremely limited resources (see above), and designating a certain area an MPA or a no-fishing zone needs iron-clad justification. Just try and tell an angler that he can’t fish somewhere, without giving a reason.
Scientific research provides us with facts, on the basis of which wise and informed decisions can be made.
The way to find out, scientifically, where sevengill cowsharks go, and what they do there, is to tag them. There is no other way to find out what they do when they’re not swimming around you at Shark Alley. The ocean is (ahem) quite large.
Once we know where they go, we can find out how to protect them. The most important sevengill habitats to conserve are those related to reproduction. The fact that Shark Alley is in an Marine Protected Area isn’t enough: the sharks don’t give birth there, and there is almost no policing of MPAs in South African anyway. A baby sevengill is about 45 centimetres long. Have you ever seen one less than a metre long at Miller’s Point? I thought not.
If you enjoy diving with the sevengills (from the shore or a boat), if you enjoy photographing them and winning photo competitions with your images, if you make money from taking other divers to see these sharks, or if you’re in favour of making the best effort to get the maximum results with the very limited conservation resources that are available in South Africa, then I hope you can see that this is vital research for the future of the species.
What sort of tags are used?
There are two types of tags suitable for use on sevengills. The primary one is acoustic tags, which send out a ping every two minutes. Receivers placed in False Bay and around South Africa’s coast (many of them part of the Ocean Tracking Network) register and save these pings when a shark is close enough (up to 500 metres away in deep, still water; significantly less in shallow, noisy areas). The data is downloaded from the receiver after retrieving it from its position in the sea.
Acoustic listening device
Acoustic tags are about the size of your little finger and are surgically inserted into the shark’s abdomen. The procedure takes approximately two minutes and the incision heals remarkably fast (as animals that bite each other during mating, it’s in a shark’s best evolutionary interest to be a fast healer). Their battery life is measured in years, so a tagged shark can provide data over multiple reproductive cycles. This is how large scale movement patterns are picked up, much like the white shark research in the US that I wrote about recently. This enables scientists to identify what the sharks use different areas for.
The other type of tag that has been used on three of our local sevengills so far is a pop up archival tag (PAT). Meaghen McCord explained these tags to us when she talked about her research on bull sharks in the Breede River. These tags are applied externally and programmed to release from the shark and float to the surface after a certain number of days. On the surface, they broadcast their location and start transmitting some of the data that they’ve collected. The full suite of data, including diving depths, is only accessible if the tag is physically retrieved.
What results have been obtained so far?
So far seventeen female cowsharks have been tagged with acoustic tags. The tagging was done in March, at Shark Alley. Blood and tissue samples, from which hormone levels can be obtained (to indicate a readiness to mate, or pregnancy, for example), were also taken.
Three PAT tags were deployed. One popped up after 48 days far out to sea on Agulhas Bank, the other came off after 88 days between Gordon’s Bay and Pringle Bay, and the third came off after 136 days close to Silwerstroom Beach on the West Coast, just before Langebaan. The cowshark whose tag popped off on Agulhas bank had spent most of its time at depths between 10 and 60 metres. The West Coast shark had spent the bulk of its time between 10 and 40 metres’ depth. The False Bay shark, interestingly, recorded most of its time at depths of between 40 and 60 metres – pretty much the maximum depth you can get in False Bay. So it didn’t just hang out at Shark Alley while in False Bay!
More detailed results will be made available on the Shark Spotters blog. It’s early days yet!
How you can help
Go and like the Spot the Sevengill Shark – Cape Town page on facebook. Then get your camera out and go for a dive, or dig through your photo library. The researchers are looking for photographs of sevengills taken from above, with the following accompanying information: the date, the shark’s gender (males have two external claspers, females have smooth abdomens), and the location. Software and some human intervention (when the computer falls over) will be used to identify sharks by the markings on their bodies. This will enable the researchers to build a database of shark individuals, and to track their presence at the known aggregation sites visited by recreational scuba divers.
There is a slightly similar citizen science project on sevengills happening in San Diego. It’s very exciting for us to be able to advance the cause of a species that is so charismatic and beloved by the Cape Town diving community.
Grumpy sea has thrown lots of kelp onto Scarborough beach
Scarborough is a conservation village, quite remotely situated on the Atlantic coast of the Cape Peninsula, just north of Cape Point. It’s very unspoiled, and its unique charm is jealously guarded by its residents. If you’re a bird watcher, or are desperate to escape the metropolitan charms of central Cape Town (or the hustle and bustle of Sun Valley, like us), this is a wonderful place to spend some quiet time close to the ocean.
To finish off the deluge of photographs taken while on board the boat while we were on our liveaboard trip to the Red Sea, here are some pictures of the scenery
Pimped out scooter in Hurghada
Private beach at the Marriott
Private island at the Marriott
Shipwreck near the Hurghada marina
Cliffs on the Sinai Peninsula in the Ras Muhammad National Park
Shallow water where the reefs are is lighter in colour
Hazy desert landscape
Liveaboard anchored at a reef
Reef
Liveaboards at the Thistlegorm
Liveaboards at sunset
Special Kate
Clouds at sunset
More sunset
Pink clouds
Hurghada
Boats at the fuelling station in Hurghada
Tony at the fuelling station
Fishing boat
Packing ice on board
The mosque in front of Hurghada marina
This ferry goes across to Saudi Arabia
The mosque in Hurghada
Shipwreck at sunset
Sunset at Hurghada marina
Flying in to Hurghada the reefs are visible from the air
For a change the weather looks good for the weekend. I cancelled last weekend but that was a mistake as the conditions turned out to be good (loud self inflicted slap). The wind won’t be too strong, and the swell is from the south east which means flat sea along the Atlantic seaboard. I would like to dive North and South Paw on Saturday from OPBC and possibly do a double tanker to Justin’s Caves on Sunday. Text or email me if you want to dive.
Last week’s diving
Wild wind and grumpy sea in False Bay has had us on the Atlantic coastline most of this week. We have done a few trips to Duiker Island and spent an afternoon just off Oudekraal. The water is cool and clean.
We did manage a warm(ish) dive in False Bay on Tuesday when we were fortunate to take two media people for a dive along the new shark exclusion net in Fish Hoek. It was spring low tide so we could almost have walked out to the end of the net, but the idea was to get some photos and a positive story out on the merits of the net, the work involved in deploying and retrieving it and the conservation efforts behind it all. An article appeared in yesterday’s Cape Argus – you can read it here and see some photos from the day on facebook.
Over-under view of the exclusion net at Fish Hoek
Sevengill cowshark project
There is a huge amount of work going on to try and establish a photo ID project for the sevengill cowsharks that hang out at Shark Alley. Its a dive most people really enjoy and very little is know about their movements and habits. Please go and like the project’s facebook page and if you have anything to contribute… info, stories etc… please do so! All the information about what is required for the project can be found on the facebook page.
Pool deck at home is complete
Festive season diving
Lots of public holidays and annual leave happening over the next few weeks means we will try and schedule more weekday diving than normal. I will send out text messages if I schedule dives in between newsletters – let me know if you don’t usually get texts from me (and want to), and I will add you to the sms list.
Things are looking so good at home now – we just got the pool deck finished – that I’m looking forward to spending some time doing confined water skills with my Open Water students too!
Long Beach, Noordhoek (not to be confused with Long Beach, Simon’s Town) is the most wonderful beach in Cape Town to walk on. It’s spacious, scenic, dog friendly, and sometimes you can see horses there. It goes on for miles. The water is freezing cold. There are a couple of places to surf, with a Shark Spotter on duty at the Chapmans Peak end. Also, there’s a shipwreck if you walk far enough (just don’t go alone – it’s not safe).
Tony and I watched this team of huskies running up and down the beach just before sunset one beautiful afternoon late last year. I think they are part of Mush It Up Sledding. Beautiful dogs doing what they were born to do: run! In the background some surfers get a few waves in before it gets dark.
