Category: Beach

Article: Scientific American on why whales beach themselves

Here’s a timely link to a Scientific American article about why certain kinds of whales beach themselves. The article references a mass stranding in 2009, of 55 false killer whales that took place on Noordhoek beach. An interview with a neuroethologist (she studies animal behaviour and how it is controlled by their nervous systems) and expert in marine mammal auditory processes says:

I have to provide the caveat that strandings we know going back to Aristotle, meaning they may be a natural phenomenon. That raises an interesting question: If you have an animal and it is stranded and you insist on returning it to the sea, are you harming the population? If they are sick or diseased, what are we doing to that population pool? I’m not advocating that we don’t rehabilitate animals, if we can. We should understand causes of stranding, but we also have to accept the fact that strandings may be in many cases natural phenomenon.

Wikipedia lists some likely causes of mass strandings. The whale that beached itself at Strandfontein in the third quarter of last year was in extremely poor health, and this was most likely part of its process of dying.

The scene outside Bertha's Restaurant on Sunday
The scene outside Bertha’s Restaurant on Sunday

On Sunday 24 March, a pod of twenty false killer whales beached themselves on Noordhoek beach. (It was originally thought that the whales were pilot whales.) The NSRI and the City of Cape Town as well as teams of veterinarians and other experts (both assisted and obstructed by members of the public) worked with the whales for hours, during which time several died, one swam away, and five were released out of Simon’s Town. One released whale swiftly beached itself outside Bertha’s Restaurant in Simon’s Town around lunchtime yesterday,  where Tony and I caught a glimpse of NSRI members holding it with its nose towards the sea while waiting for assistance. Another three of those whales beached themselves on Long Beach, Simon’s Town, late on Sunday night and had to be euthanased.

NSRI volunteers holding the false killer whale's blowhole above water
NSRI volunteers holding the false killer whale’s blowhole above water

A situation like this is very upsetting for humans, as it is difficult to see otherwise majestic and highly intelligent creatures lying helpless out of their natural element. It is not surprising that emotions ran high at Noordhoek beach on Sunday. Unfortunately these mass strandings – which, the vast majority of the time, are natural events caused by ill-health or magnetic anomalies of the earth’s crust – usually do not end well.

One doesn’t expect children to realise the gravity and probable outcome of a stranding (in fact, I don’t think children should be allowed anywhere near stranded marine mammals – it is far too upsetting and highly unlikely to end the way the Free Willy movie does). Those who work with marine animals and the ocean, however, would (or should) be well aware of how unlikely it is that any significant number of the whales would survive. I think it is unfair to suggest that the City of Cape Town, NSRI, and veterinarians on duty would euthanise the whales as a convenient way out, or because they were tired of trying to save them. In light of this, some of the behaviour at Noordhoek last Sunday was frankly embarrassing. Nan Rice of the Dolphin Action Protection Group delivered a justified slapdown of the parties involved in a letter to the Cape Times published on 26 March.

For a mind-expanding look at why our efforts to assist stranded marine mammals could be completely misguided, I wish you could all listen to Whale Song by Not the Midnight Mass. I’ve been looking for a video or the lyrics since I first heard it performed in concert. If I find it, I’ll share it. It’s both beautiful and thought provoking.

Read the full Scientific American article here.

Trial deployment of shark exclusion net at Fish Hoek beach (part II)

The net lies in the calm water after a successful deployment
The net lies in the calm water after a successful deployment

Here’s the rest of the set of photographs I took on Friday 22 March of the shark exclusion net being deployed for the first time at Fish Hoek beach. There’s a press release about the net here (or here – read it). If you’d rather flick through a facebook album of photos, there’s one here.

For your edification, I reproduce the FAQ part of the press release, which answers some common concerns about the net:

Q. Where will the net be placed?
A. The net will be placed in the corner near Jagger’s walk, enclosing the space (approximately) between the City of Cape Town Law Enforcement offices and Jagger’s walk, including the area in front of the Galley Restaurant. It will extend approximately 300 metres out to sea.

Q. Will the net be permanently in place?
A. No. The net will be deployed and removed on a daily basis. It was determined that leaving the net unsupervised at night would pose an unacceptable risk for entanglement of marine life, such as whales or dolphins. This arrangement will mean that the net is supervised at all times, thus allowing the net to be removed should whales, dolphins, or other animals be deemed to be at risk.

Q. How long will the trial last?
A. The City has received permission from the National Department of Agriculture, Forestry and Fisheries, and the Department of Environmental Affairs to trial the net under a research permit. This permit is valid until the end of January 2014, after which the programme will be evaluated and a longer term approach developed.

Q. What type of netting will be used, and why was the mesh size chosen?
A. The net is made of thick HDPE twine, with a small mesh, 45mm X 45mm in size. The mesh is hung “on the flag” i.e. in a square configuration. This mesh size and configuration significantly reduces the risk of entangling large marine animals, as well as small fish.

Q. Is the exclusion net like the shark nets in KwaZulu-Natal? Why can’t the KwaZulu-Natal shark nets be used here?
A. No, this net is different from the KwaZulu-Natal nets. The shark nets in KwaZulu-Natal are essentially large-meshed gill nets that entangle and catch sharks, reducing the local shark population and thus reducing the risk of shark attack in the vicinity of protected beaches. The City of Cape Town has committed to ensuring that marine life – including sharks – in our coastal waters are protected; nets similar to those used in KwaZulu-Natal would not be acceptable in light of that commitment.

Q. How safe will swimming be when the net is deployed?
A. It is important to note that the aim of this net is create a safer swimming area. The City of Cape Town cannot guarantee the safety of anyone using the netted area; use of the area will be at the swimmer’s own risk. However, the City is of the opinion that the safety of swimming at Fish Hoek beach will be improved, and that the presence of the net will considerably reduce the risk to swimmers.

Q. Will people be able to surf/kayak/body board/operate watercraft within the netted area?
A. The netted area will be primarily for the use of swimmers. No motorised or non-motorised watercraft will be allowed within the netted area. Inflatables will be permitted. Body boards will be allowed within the netted area; however at peak times users may be asked to leave if they are posing a risk to other water users in the netted area.

Q. What hours/days will the net operate?
A. It is intended that the net will ultimately operate according to the same hours as the Shark Spotters, i.e. 07:00 to 18:00 in summer, and 08:00 to 17:00 in winter months. This is to ensure that the net is supervised at all times. This will remain subject to change during the start of the trial period while different configurations and procedures are being tested. Additionally, deployment of the net will always be subject to weather conditions which may necessitate that the net is deployed later than expected or removed earlier than expected each day. It is not possible to determine ahead of time which days the net will operate on and for how long it will operate each day – this decision will be made daily based on weather and sea conditions. However, the net will be available to be deployed every day, and the deployment crew will be on standby daily to ensure this.

Q. Will swimmers be required to leave the area if a shark is spotted?
A. Initially, the normal provisions of the Shark Spotting Programme will remain in place. If a shark is spotted in the area, the siren will sound and all users within the netted area will be required to leave the water. This is to ensure the safety of the public. This decision will be reviewed at a later stage, after research on the response of sharks to the net has been completed and analysed.

Q. Will whales/dolphins/seals/sharks/fish get trapped or entangled in the net?
A. The City is taking every step to reduce the risk to marine life. In addition to the small mesh size, and the decision to remove the net at night, the netted area will be under constant supervision by the Shark Spotters. This will allow the Shark Spotters to take action should marine mammals approach too closely to the net, including removing the net, or gently herding the animals with a boat. It is not believed that sharks are at risk of entanglement, due to the small mesh size. It is possible that there may be some entanglement of small fish, but this is not likely.

Q. What will the impact of the net be on the trek fishers?
A. The trek fishers have been extensively consulted as part of this project. The City believes that the net is not likely to have a significant impact on the ability of the trek fishers to operate in the area. Additionally, the Shark Spotters have contracted the trek fishers to assist with deploying and removing the net on a daily basis, due to their familiarity with the area and their ability in handling nets. The net may be removed at times to facilitate fishing, but will be returned once this is completed.

Q. Who will manage the net?
A. The Shark Spotters will manage the net for the City. The City has extended its existing Memorandum of Agreement with the Shark Spotters in order to allocate the additional responsibility.

Q. Were specialists consulted in the design of the net?
A. Yes. A number of experts were consulted, including the KwaZulu-Natal Sharks Board, the National Department of Agriculture, Forestry and Fisheries, and the Department of Environmental Affairs, as well as trek fishers, City engineers, and coastal engineers in the private sector.

Q. Has this approach been used anywhere else in the world?
A. No. Exclusion nets have been used successfully in Hong Kong and more recently in the Seychelles, however these are fixed nets that are not removed daily. This is a globally unique project that is being monitored by a number of governments around the world – if it proves to be successful, it is possible that it may be replicated in other countries.

Q. How will this trial be evaluated?
A. The net will be the subject of an ongoing scientific investigation, which will look at a number of aspects, including: Ecosystem impacts and the potential for marine animal entanglements; the logistical viability of daily deployment and retrieval; impacts on the trek net fishers; behaviour of the net under a variety of weather conditions; and public response to the net and use of the area. The decision to continue the operation of the net on a more permanent basis after the trial period has ended will be based on an assessment of these variables, in conjunction with the National Department of Agriculture, Forestry and Fisheries, and the Department of Environmental Affairs.

Trial deployment of shark exclusion net at Fish Hoek beach (part I)

Breaking dawn, minus the vampires
Breaking dawn, minus the vampires

A shark exclusion net has for some time been planned for Fish Hoek beach. The net will not kill sharks and other marine creatures like the ones in KwaZulu Natal do, but rather forms a close-meshed barrier that aims to keep sharks out, swimmers in, and everyone alive. For reasons outlined here, the process of designing and building the net has been a fairly lengthy one, and something that neither the City of Cape Town nor the Shark Spotters wanted to be hasty about.

It was therefore a happy day last Friday (22 March) when the first trial deployment of the net was conducted at Fish Hoek beach. The net is a world first, and it will take a couple of practice attempts by the parties involved (the City, the trek net fishermen who will do much of the work to deploy the net, and the Shark Spotters who will monitor it) before it’s a smooth process. The net will be put out each morning (given suitable conditions) and removed in the evening.

The net in its trailer
The net in its trailer

On Friday I spent the morning on the beach, watching the process, enjoying the beautiful calm weather, and taking photos. I spoke to a number of community members – mostly elderly people who come down to Fish Hoek every morning for a swim – and they were unreservedly enthusiastic about this “historic” project.

There is a press release regarding the net here. I suggest you read it. There’s an album of photos on facebook, here.

A Day on the Bay: Naval exercises at Long Beach

Date: 7 March 2013

Approaching the beach
Approaching the beach

Sometimes you don’t even need to get on the boat to see something entertaining. Earlier this month, while working with Advanced students at Long Beach, we were privy to some very entertaining activities. The SA Navy was conducting a training exercise involving disembarkation from a boat, running up the beach, and assuming a combat stance.

Ready to disembark
Ready to disembark

They carried on for hours. Clare and I ate dinner at the beach around 7pm that evening, and they were still busy. In fact we were asked to leave at one point because it had “become an operational area”.

Ready for combat in the parking area
Ready for combat in the parking area

Newsletter: Boat racing

Hi divers

The weather has not been too kind this week if you are a diver. For anything else the mild winds, sunny days and pleasant evenings have made for a nice week. Ocean wise, not so much. Last weekend was blown out completely and despite the shoddy weather the divers that did head out on a boat from Hout Bay returned very quickly. Monday was flat calm and pleasant but the viz was not great. We did a seal trip to Duiker Island and the viz was 6 – 8 metres, and the water was cold.

 

Happy snorkelers at Duiker Island
Happy snorkelers at Duiker Island

 

During the week we have been in False Bay with some places having 2 metre visibility (Photographer’s Reef) and others 6 metres. Long beach today was 3-4. The navy were doing training and there were boats buzzing over us all through the dive and lots of armed soldiers running around on the beach and on and off the boats. They were still busy after seven o’clock this evening. Diving at Long Beach without a buoy is a risky pastime.

Running a seal snorkeling trip
Running a seal snorkeling trip

The weekend

The wind tomorrow will have some effect on False Bay and might clean it up a little but there will still be a 4 metre swell cruising into the Bay. The swell is more southerly than westerly so I think its going to be a hard call.

It’s the Argus Cycle Tour this Sunday so we will be totally boxed in, here in the deep south, and won’t leave home at all. My feeling is that it’ll be a dry weekend once again.

Green water at Strandfontein
Green water at Strandfontein

Training

I have both SDI and Padi Open Water students diving, a Rescue and a Divemaster course so it’s been good being busy. However I did have an engine failure on the port motor of Seahorse that is going to take a while to fix. The boat dives we plan will then be on one of the other charter boats for a few weeks.

Travel

Don’t forget our Durban trip from 14-18 June – contact me if you’re interested. Clare and I are going to the Red Sea in October (dates to be finalised in the next few weeks) and wouldn’t mind some familiar faces on the boat. If you want more information on that trip, let me know as well.

regards

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

Diving is addictive!

Friday poem: The Shark

The scientific name of the white shark is Carcharadon carcharias. The Carcharadon part comes from a Greek word, Karcharos (in the poem below) which means “sharp”. For a poet who lived from 1836 to 1920, this is a remarkably prescient poem, as in its final line the poet exhorts the shark to “learn of Man, to fight” in order to survive.

The Shark – William Henry Venable

Captured! Along the beach those shouts reveal
The fisherman exultant victor! Hark!
The Karcharos, from out his crystalline, dark
Blue lair by rud of flesh and lurking steel
Bewrayed, hath ravined down with his last meal
Death as a gobbet. On the hot sand, stark,
He gasps and shudders agonizing. Mark!
With horrible grin those bloody jaws appeal
Unto his gloating murderers.—No more
Those serried ranks sextuple of fanged white
Shall scare the shallows and appall the shore,
Never again wreak havoc and affright,
Ranging the Gulf Stream, weltering in gore;—
Poor Shark! Man-eater! learn of Man, to fight.

Lecture: Alison Kock on Shark Spotters

The Save Our Seas Shark Centre in Kalk Bay held another marine speaker series this November, and Tony and I attended a couple of the talks. One which we enjoyed was given by Alison Kock, research manager at Shark Spotters. Shark Spotters is a beach safety program that Capetonians are rightly very proud of – there’s more about it on the Shark Spotters website, here and here. Alison’s talk focused on some updates as to the research that is going on in False Bay, and extensions of the spotting program.

Updates on the shark spotting program

Between 2004 and 2012 the shark spotters have made more than 1,400 sightings of white sharks, 60% of which resulted in beach closures. The sharks are either resting, passing by, or searching for prey (other sharks, rays, fish) when they come inshore in summer. For spotting to be effective, at least 40 metres of elevation is required from which to observe the beach. The beaches in False Bay differ, in that sightings at Muizenberg resulted in a beach closure only 30% of the time, while at Fish Hoek the beach was closed 80% of the time. This is because of the nature of the surf and sharks’ behaviour at the different beaches.

At Muizenberg, the backline is some 300 metres off the beach, and the majority of the time sharks are cruising along behind the backline or further off the beach. The beach is only closed when sharks enter the surf zone – 74% of the time they are simply swimming past the beach. When a shark is behind the surf zone, the red flag is raised (for High Shark Alert) but the beach remains open.

At Fish Hoek, 61% of the sharks remain behind the breakers, but this is a mere 50-100 metres from the beach. 68% of the sharks are swimming past, but their proxmity to the beach means that more beach closures take place than at Muizenberg. The lookout location at Fish Hoek is on the mountainside, 110 metres above the beach.

Shark exclusion net at Fish Hoek

Fish Hoek is to be the site of a trial shark exclusion net that will be tested in the next month or two, all going well. It’s important to understand that this is an exclusion net, not a gill net, and the team in charge of the trial have been mandated to design and construct a net that will not lead to bycatch of any marine species. The aim is not to kill sharks and reduce the population, thus reducing the chance of interactions with people (this is what the Durban nets do), but rather to build a “wall” in the sea to keep them out of a specific area of Fish Hoek Bay in order to make it safe for swimming.

The other important thing to remember is that nothing like this has ever been done before.  Owing to the strength of the wind and swells that we experience in Cape Town’s summer, and the presence of large amounts of kelp in False Bay which can foul the net, the net will only be deployed on calm days and will be removed overnight. The net has been designed and is being constructed at the moment, but the process of deploying and removing it (to be handled by the trek fishermen) will be a learning experience initially. If the initial prototype has flaws, the City of Cape Town is determined to iron them out and make it work. It would be courteous and generous of the media and other observers to recognise that this is a world first, and to allow for an initial period of change and possible disruption as the net is tested and refined.

New spotting locations

Earlier this year, Caves at Kogel Bay (on the eastern side of False Bay beyond Gordon’s Bay) was added as a spotting beach. This is a popular surfing location and the water is relatively deep as much of the coastline in that location is rocky cliffs. There have been numerous sightings there since spotting commenced, confirming that this site seems to be on a route that white sharks take in and out of False Bay.

Monwabisi Beach on the northern end of False Bay is the site of up to 10 drownings per year, owing to dangerous rip currents that are, in part, a result of artificial structures constructed for swimming (see the satellite image below). Shark Spotters is adding Monwabisi Beach to the list of regular beaches that have spotters on duty. This is an exciting development and will be particularly important if the proposed oceanfront development along Baden Powell Drive takes place.

[googlemaps https://maps.google.com/?ie=UTF8&ll=-34.074071,18.687294&spn=0.006185,0.009645&t=h&z=17&output=embed&w=425&h=350]

SharkShield research

South African researchers collaborated with scientists in Australia to test the effectiveness of SharkShield, a portable device for use by surfers and divers and intended to repel sharks with a magnetic field. The South Africa researchers towed a seal decoy at Seal Island with the SharkShield attached, while the Australians tested it in natural predation situations. They found that the device does not attract sharks (this I imagine would be the absolute minimum functionality required before one even considered using it!). The device repelled some sharks, but not all of them, and its effectiveness depended on the shark’s state of mind. The range of its effectiveness was found to be about 2 metres diameter from the object. The full research study is available here.

Safety tips

Sign at the end of Fish Hoek beach
Sign at the end of Fish Hoek beach

Alison concluded her talk with some shark safety tips, of which it’s good to remind oneself of once in a while (specially in summer):

  • Be aware of your surroundings. The presence of dolphins, bird activity, or fishing may indicate that white sharks will be in the area. Don’t let the cute dolphins distract you and get your guard down!
  • Check out recent sightings. Visit the Shark Spotters facebook page, and make sure you understand the flag system and read the signs at the beaches you visit.
  • Don’t swim at night, in low light (sunrise and sunset), or in murky water (such as at a river mouth) or poor visibility.
  • Stay in shallow water. Three quarters of shark activity at our beaches is behind the backline.
  • Avoid high risk times and areas when you go swimming.
  • Stay in groups – don’t get separated or swim out far beyond the other water users.

Dive sites: HNMS Bato

Christo (behind water droplet) enters the water at the end of Long Beach
Christo (behind water droplet) enters the water at the end of Long Beach

I have wanted to dive HNMS Bato for some time, but the 450 metre walk down Long Beach to reach the entry point for the wreck deterred me. The 450 metre walk back to the parking area enthused me even less. A full set of diving gear weighs at least 25 kilograms, assuming a 6-7 kilogram weight belt, and one isn’t particularly mobile in a wetsuit. Christo has dived this wreck a few times on his own, and one breezy Saturday, feeling strong, I joined him.

Burnt edges of the deck
Burnt edges of the deck

Unlike the area of Long Beach along the pipeline, this is a very infrequently dived site. The Bato was a Dutch (the “N” in “HNMS” stands for “Netherlands”) warship that caught alight and sank on 8 January 1806, after being used as a floating battery. She lies in relatively shallow water – less than 5 metres deep at high tide – so we took extra weight with us to ensure that we could stay on the wreck.

The wreck is thus over 200 years old, and was partially burned before she ran aground and sank, so you should manage your expectations accordingly. That said, large areas of decking are visible, as well as rivets, studs, and some holes in the wood where some of these have rusted away. Much of the wreck must lie under the sand, and the entire remaining structure, which is not more than a metre off the sand at its highest point, is covered with a dense layer of kelp and sea lettuce. Diving her is thus an exercise in patience: one hangs (sometimes made difficult by surge) in a spot, and waits for the kelp to move away to reveal what’s underneath.

Copper sheets with holes for rivets
Copper sheets with holes for rivets

There are many large pieces of crumpled copper sheeting sticking out of the sand. I was also intrigued by what looks like ballast stones on the wreck site. There are “runways” of pebbles (each about the size of two fists) lying lengthways in amongst the wreckage. I wonder whether these are part of the ballast that was in the bottom of the ship, or whether it’s just suspiciously regular patterns of river stones that have washed into the sea off the beach.

One of HNMS Bato's cannons
One of HNMS Bato’s cannons

It goes without saying that you shouldn’t try to remove anything from this wreck – it is over 60 years old and thus protected. In any case, if you have piratical tendencies, it has been thoroughly worked over, so nothing that remains is portable. The cannons from the wreck (luridly painted) stand outside the Simon’s Town post office or on the jetty outside Bertha’s (which is just below the post office).

I don't know what this indentation is but it looks interesting!
I don’t know what this indentation is but it looks interesting!

The marine life on the wreck is intriguing. We have seen large numbers of large pyjama catsharks there, sleeping under the deck in a space that is about 40-50 centimetres high off the sand. A torch is required to fully appreciated the creatures that live in this space. There are also beautiful cushion stars, orange clubbed nudibranchs, two tone fingerfin, and some schooling hottentot that like to hang about above the kelp. Both times I have dived here I was distracted by the wreckage itself, trying to identify what the different pieces of the ship that remain were used for. I expect that on future dives I’ll appreciate the animals inhabiting the structure even more.

Some longer pieces of wood remain
Some longer pieces of wood remain

Dive date: 10 November 2012

Air temperature: 22 degrees

Water temperature: 17 degrees

Maximum depth: 4.5 metres

Visibility: 5 metres

Dive duration: 55 minutes

White Sharks – Population Monitoring, Policy and Review (part II)

This post follows on from my review of Global Perspectives on the Biology and Life History of the White Shark. That book (a collection of scientific papers) is divided into three sections, and I’m going to highlight papers that I found particularly interesting in each of the sections.

Here’s the first series of posts I did, on Biology, Behaviour and Physiology:

Here’s the post I did on Migratory Patterns and Habitat Use, and here’s the first post on Population Monitoring, Policy and Review.

White shark interactions with humans

Shark Spotters: A Pioneering Shark-Safety Program in Cape Town, South Africa – Kock, Titley, et al

This paper made me so proud! It is a detailed description of the Shark Spotters program that is run at several popular surfing and swimming beaches around the Cape Peninsula. The program was introduced in 2004, and strikes a wonderful balance between beach safety and protection for the sharks. An added benefit of the program is that a rich set of data describing shark movements at Cape Town’s bathing beaches is collected and suitable for analysis.

Here’s a taste of the sort of data gathered by the spotters between November 2004 and December 2009:

  • Average duration of a shark sighting is about 20 minutes, with maximum duration of 4 hours.
  • Muizenberg had the highest number of sightings in the data set, while Strandfontein, only 8 kilometres away, only had one sighting.
  • The beaches with the lowest number of sightings are those with the lowest elevation points from which the spotters work, and the ones with extensive reef systems nearby.
  • Clovelly and Glencairn, both adjacent to beaches with high sightings (Fish Hoek and St James), and with good elevation points, had very low numbers of sightings recorded.
  • 97% of the sightings were made in summer, peaking in October and December.
  • 74% of sightings were of sharks behind the surf zone in calm, deeper water. The rest of the sharks were in the surf zone.

This paper is absolutely fascinating, with ample illustrations including an example of the record sheet used by spotters while on duty. It includes an honest assessment of the strengths and limitations of the program. If you can get hold of a copy I’d encourage you to read it!

Responding to the Risk of White Shark Attack: Updated Statistics, Prevention, Control Methods, and Recommendations – Curtis et al

According to the authors, the recommendations in this paper

are intended to help reduce sensationalistic, irrational, or ineffective responses by decision makers and benefit the beach going public as well as vulnerable white shark populations.

Since 1839 white sharks have been implicated in 346 unprovoked attacks on humans, of which 102 were fatal (the highest number of fatalities of any species). Most shark bites are attributable to more common sharks such as the bull shark, the white shark is most frequently cited where the species involved is identified without doubt. There has been an increasing trend of attacks during the last century as recreational use of the ocean by swimmers and surfers increased along with human populations on the coastline and the development of warmer and warmer wetsuits and other gear that allows people to spend longer periods in the water. Over the same period the fatality rate from white shark bites has declined significantly owing to improved medical care and faster emergency response times.

Of particular interest to me was the South African data in this paper. White sharks have been implicated in incidents in three of the four coastal provinces: KwaZulu Natal, the Eastern Cape, and the Western Cape. Between 1990 and 2009 there were 120 shark attacks in South Africa (about 6 per year), of which 15% were fatal. White sharks were involved in 47% of the bites, and 67% of the fatal incidents took place in the Western Cape, the centre of the white shark’s distribution in South Africa. The Western Cape has 10 of the country’s 13 Cape fur seal colonies, many of which are close to the coast. These colonies are important feeding grounds for white sharks.

White shark bites in the Western Cape took place throughout the year, with (this surprised me) 51% occurring between April and July. Of the victims, 39% were snorkeling or free diving (spear fishing), 30% were surfing, 15% were surf-ski riders beyond the surf zone, and 9% were scuba divers. The Eastern Cape attacks were all on surfers except for one, and peaked in July. This area is thought to include the pupping grounds for white sharks off Southern Africa.

Sharks attack humans for defensive purposes, or because they are hungry. The second motivation is the more common, and there is evidence to suggest that white sharks do not spend extended periods of time identifying their prey as a potential food item before striking, but rather attack first and if it is unpalatable do not complete the predation. Most attacks on humans involve a single bite, and very rarely does the white shark consume its entire victim.

The authors go on to review exhaustively the various responses possible to shark bites on humans, both lethal (such as hunts, culls and nets) to nonlethal (Shark Spotters leading to beach closures, barriers, tagging and research aimed at control, education and procedures to prevent shark bites). The authors also give advice on dealing with the media after an incident, and conclude with the following recommendations to reduce white shark-human interactions:

  1. Study the area and its sharks
  2. Develop a protocol to be followed after shark incidents
  3. Educate the public about high risk areas, times to use the water, and behaviours (such as spearfishing)
  4. Avoid public shark hunts. There is very little evidence that these activities are effective.
  5. Conserve white shark populations as far as is practical.

Friday poem: No Place Like Home

Stephen Cushman celebrates the connection to family, both blood relatives and marriage connections.

No Place Like Home – Stephen Cushman

My ocean’s the one bad weather blows out to. To face the other, waves all driven by prevailing winds, I have to turn my back on my family. May they forgive this westward spree, my losing my head to ravens that ride the thermals in circles, to the shrub-covered bluffs of coastal scrub and chaparral, to coons in the avocado trees; may they not worry that I see signs warning Great White Shark Area, Rutting Elk May Be Aggressive, and Hazardous Surf, or that one night two quick earthquakes burped through the ground; and may they repeat, when I return slightly burned from the land of poppies, all the lessons they ever taught me about ordination in the ordinary.