Shark Banner

by Ian Robertson

From time to time sharks and shark attacks have gained headlines in Western Australia and elsewhere. This page has been prepared to introduce commonsense and fact into an often emotional debate.

  1. The ocean is a wilderness and we must accept its inherent risks when entering it. 
  2. The risks posed by sharks are minimal, compared to other ocean-related risks, and the shark-related risks can be further reduced by taking some basic precautions – see below.
  3. Electronic deterrents are available and are likely to be much more effective than any blind killing of sharksl.
  4. Most shark culls target sharks of reproductive age – hardly conservation. Shark culling is an anthropocentric approach typical of the 1960s, which we should have out-grown by now.
  5. Survival of a hooked shark, even if set free, is questionable.  It has already been demonstrated that some sharks are attacked, killed or injured while hooked, which is unacceptable,
  6. The not insignificant funds directed at a shark cull would be better spent reducing our road toll and dealing with alcohol and drug abuse.  More lives might be saved.
  7. Sharks have an important role in the eco-system, as any predator, so it is unwise to disturb its balance.
  8. Shark fishing and deliberate killing and torturing of sharks is deplorable. This activity only serves to attract sharks to beaches where the public swim, enhancing risk to others.

Below is some common sense on sharks from my experience over many decades as a scuba diver .  I hope this appeals to those with a rational turn of mind.

Fear of sharks and other sea monsters has been with us for a while. In fact, fear of being eaten is a basic survival instinct. The story and later the film ‘Jaws’ has brought this fear into sharp focus onto the Great White Shark, demonising it.  This is a comparatively rare shark but it can grow large and it can be lethal. Let’s examine this fear and see if it is altogether justified. Later, you may like to look closely at how much this fear has diminished your activities in the ocean and the fun you have from diving and other ocean sports.

Fear per se generally arises from the unknown; i.e ignorance. Reduce ignorance, replace it with understanding and respect, and much of the fear evaporates. This is what separates rational modern man from the superstitious and the primitive. Ill-informed political and media hype is of little worth and only fosters squalophobia.

Potentially dangerous sharks
Some quite specific large shark species over about 2.5 - 3 metres are potentially dangerous to humans. They are dangerous in that they can do harm: whether they will is quite another matter, depending on conditions, hunger, opportunity, their safety, and mainly food preference. Most sharks feed on fish, rays, smaller sharks, octopi, squid, crustaceans, turtles and birds. Divers are not on that list. That said, any large shark and most small ones should be treated with respect. Among ‘dangerous’ shark species are: -.

The bull shark (Carcharhinus leucas). This potentially aggressive, omniverous shark is found inshore in tropical, warm, temperate seas (Sydney to Perth) and is the only species that penetrates far into fresh water, gaining some notoriety in the Swan River. It matures at 2 m, reaches over 3 m, is unpredictable and can harass spearfishermen. However, many of us, and most diving schools, dive in Perth’s Swan River, without even a nibble. There have been very rare attacks there on swimmers.

Bull Shark

The solidly built Bull Shark. Photo by Brook Ward.

The tiger shark (Galeocerdo cuvier) has a particularly big mouth, matures at 3 m and reaches 6 m. This relatively warm water shark is particularly active at night, coming close inshore and near the surface. It is an indiscriminate feeder (scavenger) and appears very confident. It has characteristic vertical stripes and a long, very straight upper lobe to its tail. The stripes fade with age. Numerous divers have seen them without being threatened. I have had two such encounters. They are curious (this is not aggression!) and might come in for a look.

Tiger Shark

The Tiger Shark. The stripes become less defined with age. Note the round black eye and the straight upper tail lobe. Photo by Jim Abernethy.

The rare oceanic white tip (Carcharhinus longimanus) is a warm-water, open-ocean shark. It matures at about 2 m and reaches 3 m. Its back is bronzy grey and is paler underneath. It has characteristic very large, rounded, white tipped dorsal and pectoral fins and can be very persistent. It is seldom seen.

Oceanic White tip

The Oceanic White-tip. Note the rounded dorsal and pectoral fins with white markings. Pilot fish are common with this shark. Photo by Masa Udioda.

The great white shark (Carcharodon carcharias) is as poorly understood as it is rare. Although it has a global distribution, it prefers cooler waters of the Great Australian Bight, southern South Africa and N California. In common with the Mako (Isurus oxyrinchus), it has a heat exchanging circulatory system, allowing it to maintain a body temperature above that of the ambient seawater. Thus, it is very active and has a substantial need for ‘high energy food’. It is born at about 1.3 m, eats mainly fish, rays and other sharks until it reaches 3 m, when it is big enough to include blubber-rich marine mammals (seals, sealions, whale calves). It sexually matures at 3.5-4.0 m and can attain 6.0 m. Its back is slate blue-grey to grey-brown with a white underside and the boundary between the two is marbled and very distinct. It has a characteristic crescent-shaped tail driven by substantial musculature in its thick caudal keel. It is a substantial shark that can accelerate in a moment from a gentle cruise to full charge. It hunts by surprise, cruising the bottom until it spots a likely target silhouetted against the surface. Surprisingly, it is generally quite circumspect, often curious and targets its prey accurately.

Many of the larger sharks are heavily scarred by encounters with prey, each other and mating. Definitely the scarred 'Lion of the Ocean'.

Great White Shark

The Great White Shark. Note the sickle-like tail, the massive, deep gill-slits, the colouring and the round black eye. Image copyright Tammy Gibbs.

Other sharks
However, there are many, many others that are far less intimidating (see Sharks and Rays of Australia by Last and Stevens, 1994, published by CSIRO). An example is the cute Port Jackson Shark (Heterodontus portusjacksoni), which we often see off Rottnest. This little fella feeds mainly at night on shellfish and sea-urchins, hatches at 230 mm, matures at 750 mm, reaches 1.5 m and is mainly found lying up in caves during the day. The harmless  but spectacular spotted zebra or leopard shark (Stegastoma fasciatum) hatches at 200 mm, matures at 1.7 m and may reach 2.3 m.  In tropical waters it is often resting on a sandy bottom. With a slow approach, you can get within two metres for a picture.

Port Jackson Shark

The cute Port Jackson Shark amid wreckage of the Key Biscayne oil rig. Photo by Ian Robertson.

Leopard Shark

The harmless Leopard Shark is often seen resting on the sand between tropical coral bommies. Photo by Ian Robertson

Those that have been to Aqwa have seen their collection of grey nurse sharks and sandbar sharks in the main tank and many divers have been in the tank safely with them, despite their fearsome appearance. Wobbegongs are sharks too, that are often seen in the Perth area. Although they are shy, don’t pull a wobbys tail or you might get a few unexpected lacerations! Leave a resting shark be! So, get to know them and be able to recognise them; take an interest!

Wobbegong Shark

The Wobbegong Shark is seen resting on the bottom in temperate or tropical waters. It should be treated with respect as it can be unpleasant if provoked. Photo CC-BY-NC-ND by Richard Ling

Encounters with potentially dangerous sharks – what to do and what not
Don’t flee, this may be seen as an opportunity and don’t flap those hands or appear injured. Keep calm, move slowly, bunch up the team and try to look like a ‘big’ target; a very good reason for buddy diving. The shark will probably take a quick look, identify you as ‘not food’ or 'too difficult' and just go about its business elsewhere. Try to identify the shark. This fleeting glimpse is by far the most common scenario. When diving, a good lookout is essential; don’t get too focussed on the small stuff. This may possibly result in more shark sightings.

Down-thrust pectoral fins and/or an arched back are signs of aggression and possibly territorial behaviour. Move out of the way and if the shark persists, go back to the boat. This is not uncommon behaviour in the handsome silvertip shark (Carcharhinus albimarginatus), which can reach 2.7 m. They are often found on tropical reefs close to very deep water and are known to make short rushes towards divers.  Persistent circling indicates interest in some food you may have or they think you have, which they detect with a very sensitive sense of ‘smell’ - let them have it and get out of the way – they generally lose interest and go away quite quickly. Overt aggression is uncommon.

Silvertip Shark

The handsome Silvertip Shark. Note the white markings on the trailing edges of all fins. Photo by Ian Robertson.

Charging Silvertip

An excited Silvertip Shark.. Note the down-thrust pectoral fins. This is more show than anything else - it makes for excellent photo opportunities. Photo by Ian Robertson.

Sharks in company can be bold. Being ‘buzzed’ can be quite un-nerving but is fortunately extremely rare. Keep your head, keep the team bunched up and go back to the boat slowly and deliberately. Sometimes returned aggression helps – a sharp bang on the nose with a camera or stick when push comes to shove. Above all, keep hands and arms well tucked in. Generally the shadow of the boat and boat ‘noises’ are intimidating to the shark and it will move off and patrol at a distance.

The Great White Shark
It frequents our WA shores more often when whales are in passage. Very occasionally some quite large ones come close in-shore to feed. They like to patrol the ‘bubble line’, which divides water disturbed by the surf from clearer water further out. Fish leaving the poor visibility of the surf zone are surprised and caught. The ‘bubble-line’ is also frequented by surfers. In the early morning or near sunset, the sharks are looking for a feed and their slate grey or brown dorsal camouflage is most effective.

Surfers can be mistaken for seals and this leads to a very few close encounters and, occasionally, a very rare attack. Surfers need to wisely assess and accept the risks they are taking, avoid poor light conditions, those grey days with an ‘oily sea’, and heed warnings from shark patrols, rather than expect their fellows to make the ocean safe for them. The sea, including its margins, is a wilderness and needs to be treated and respected as such. Fortunately, diver encounters with great white sharks are extremely rare. In almost all unintended encounters, the great white may come in for a look and just go. Some enthusiasts have even deliberately snorkeled with them, but they are unpredictable and this is not recommended.

Electronic Deterrents

Electronic shark deterrents (e.g Shark Shield) are available and generally repel predatory sharks within a 5 metre radius. This is a wise and logical choice for surfers, swimmers or divers who might wish to operate on their own or in remote locations. They are deterrents and nothing more. They are ideal for those who want to further mininise a mininal risk and are common-sense in places frequented by these sharks, particularly near seal colonies. They only work if carried, charged up and switched on of course!

Shark Shield

Electronic shark deterrents in use. Photo by Ian Robertson.

Deliberate exposure
Some tropical reefs have very large populations of small sharks. These generally are grey reef sharks (Carcharhinus amblyrhynchos), white tip reef sharks (Triaenodon obesus) and black tip reef sharks (Carcharhinus melanopterus) and these can become quite used to divers. They are generally small (1-2 m) and go about their business patrolling the reef, looking for sick, injured or unwary fish. They can come quite close (2-5 m), flick a slitted eye over the diving group and swim on. Enjoy this opportunity to watch them in their element! They are beautiful and graceful.

Grey Reef Shark

A typical Grey Reef Shark. Note the black markings on the trailing edge of the tail fin. Some have a small white tip to the dorsal fin. They congregate where the current is strong and swim effortlessly there. Photo by Ian Robertson.

Whitetip Reef Shark

A typical Whitetip Reef Shark. Note the square form of the head and the white markings on the dorsal and tail fin. Shy and often found resting on the sand or under ledges during the day but are bold at night. Photo by Ian Robertson.

Blacktip Reef Shark

A typical Blacktip Reef Shark. Note the black markings on the tips of the fins and the black and white on the dorsal fin. Shy and generally found in very shallow water. Photo by Ian Robertson.

Some reefs host huge shoals of hammerhead sharks at certain times of the year. These are there for their own purpose - mating, migration or whatever - and ignore watching divers. Some tour operators even deliberately feed sharks, or attract them with the smell of food, and this can be quite a show. Cage diving is an option for deliberate exposure to the large, dangerous ones (great white, tiger and oceanic white-tip). Cage diving can be successfully achieved without messing the water with burley.  Naturally occurring whale carcases could be utilized for this to establish shark tourism, so promoting understanding and generating income. Deliberate exposure is an excellent antidote to squalophobia!

Dangerous conditions
Shark activity can increase in twilight conditions (dusk and dawn) and even small white-tip reef sharks become quite bold. This is their feeding time, so expect this. Night or late evening dives in the tropics should be in protected lagoons, rather than adjacent to very deep water, where the larger sharks are more common. Those grey evenings or early mornings near favoured hunting grounds of great white sharks should be avoided.

Line fishing, gutting fish and throwing the bits overboard or carrying bait in your BC or catch bag will attract sharks and make them agitated. When diving is in progress and well before it starts, discourage all line fishing or related activities from the boat. Going spear-fishing? Good luck mate! Bleeding and struggling fish attract sharks like a magnet and the catch can become disputed property.

Minimising the risk
You are not part of a shark’s normal diet. When a mob of divers enters the water, blowing noisy bubbles and frightening the fish, most sharks run a mile. Dive in good visibility, and be wary near sources of food (seal colonies and fishing activities) or when near the surface. The lone diver, or a diver separated from the group, is a bit more at risk than a watchful buddy pair.

I’d give diving a much, much lower shark rating than surfing or spearfishing. Attacks on even these slightly higher risk fellas are comparatively rare – similar to being struck by lightning – so why the need for squalophobia? Those that prefer to reduce risks still further can buy a reliable electronic shark deterrent, which even works on the great white shark.  For a nil risk, stay out of the water!

For swimmers and surfers, shark patrols by aircraft or drone and shark detection by smart-buoy are a help but not perfect. Shark barriers are better but cannot be everywhere. The silhouette of a surfboard from below looks much like a great white which might explain the ferocity of attacks on surf boards - territorial defence. I would think that an electronic deterrent when surfing in a remote location is a sensible precaution.

What definitely doesn't work is shark culling by drum-line. Some 60 tiger sharks were recently unnecessarily killed off the WA coast. These provide a minimal threat. No great whites were caught!

Am I or was I squalophobic?
I saw my first shark at age 15, while spearfishing off the Mozambique coast in 1956. It was a white-tip reef shark. We gave each other a considerable fright; it went one way and I the other and that was the end of it. I definitely was squalophobic!

Later encounters were in the Red Sea, where I spent a few magic moments photographing sharks, appreciating their beauty. My turning-point was a cage dive with a 4 m Great White off Gansbaai, S Africa (see link). That, and the education I was given by the very experienced tour operators, completely reversed my view of sharks. This was reinforced by a visit to the Neptune Islands in South Australia with the Rodney Fox group for some even better cage diving. Experiences with smaller sharks were off the Maldives, Palau, Truk, Indonesia, Papua New Guinea, Ningaloo and the Rowley Shoals.

I like to think that my fear has now been replaced by admiration and respect – even wonder! Enjoy your shark encounter, when it occurs, most other divers do! With a little common sense and risk minimisation, we can all share the ocean with these magnificent creatures - as we should.