Ocean News

Red Sea Shark Attacks in Perspective

8th December 2010

Tragedy has befallen the Egyptian Red Sea resort of Sharm el Sheikh: between November 30th and December 5th five incidents of snorkelers being bitten by sharks were reported, the most recent of which proved fatal. Shark attacks in the area are incredibly rare, especially so many in such a short space of time, causing widespread speculation as to what might have triggered these events. Here we aim to provide some information to help answer some of the many questions being asked by the media and members of the public.

What are oceanic whitetip sharks?

The species responsible for the attacks in Sharm is believed to be the oceanic whitetip shark, due to sightings of one in the area shortly before the first attacks, however this remains unconfirmed and few other details on the sharks involved are available. The oceanic whitetip is a large open water shark that can be found in tropical and warm temperate seas. Although usually encountered over deep water they do sometimes come close to shore. These sharks tend to have quite a varied diet due to the sparse distribution of prey in the open ocean (it’s not too dissimilar from hunting in a desert), but display a preference for bony fish such as tuna and mahi-mahi. They are also frequently associated with mammal carrion, in particular whale carcasses. It is thought that these sharks require only infrequent meals, and that in some areas feeding on the occasional whale carcass might be sufficient to keep them going for a while. Oceanic whitetips tend to be very bold and inquisitive sharks, likely associated with it being worth investigating any potential food source when meals are few and far between. It should be noted that oceanic whitetip sharks are a completely different species to the whitetip reef shark, since there appears to have been some confusion between the two in the press.

How common are shark attacks?

Despite how it may seem from this sudden cluster, shark attacks occur very infrequently, especially considering how much time so many people spend in the sea. Using data from the International Shark Attack File over the past 10 years, there has been an average of 64.6 attacks per year around the globe, 7.3% of which proved fatal. To put the relative risk of fatal shark attacks in context (using data from the past decade in the USA) the risk of death by drowning is approximately 3,000 times greater; the incidence of fatalities from boating accidents is over 300 times greater; and fatalities caused by domestic dogs are almost 30 times as frequent.

How severe are most shark attacks?

As mentioned, only a small proportion of shark attacks result in loss of life. Researchers at the University of Florida have formulated a scale to grade the severity of shark bites, similar to that used for categorising burns. The scale, termed the Shark-Induced Trauma (SIT) Scale, assigns scores to clinical findings (such as blood pressure, location and depth of injury, damage to the organs and death) in order to designate a value between 1 and 5. For instance, an abrasion to an extremity would simply score a 1 on the SIT scale, whilst a large bite to the thigh that severs the femoral artery and is subsequently life threatening would score a 5. In Florida, dubbed by press as the ‘shark attack capital of the world’, shark attacks that only result in small lacerations account for more than 90% of injuries.

Why do sharks bite people?

Unfortunately it’s very difficult to determine why people are bitten by sharks as it happens so infrequently and there is rarely reliable information on the conditions at the time. However, there are a number of theories as to why sharks might bite people, particularly in the context of the present attacks in Sharm el Sheikh.

One possible reason is simply out of curiosity. Sharks, and many other marine species, may investigate unknown objects in the ocean to determine what they might be and whether they might be edible. This might be particularly true of opportunistic open water sharks that encounter food only infrequently, such as oceanic whitetips. Without any hands to feel, sharks may use an investigatory bite to gather more information about unknown objects; their mouth is essentially an exploratory tool. This is consistent with most shark attacks not going further than a single bite and why so many shark attacks rate lowly on the SIT scale. However, what may just be a curious nip for a shark can be incredibly severe for us, with subsequent blood loss being the most frequent cause of death, as opposed to actually being ‘eaten’ by a shark.

Despite sharks’ incredibly sensitive senses, it is possible to make mistakes, resulting in one school of thought being that some attacks are the result of mistaken identity – confusing people with their normal prey. For instance it is thought that snorkelers splashing about at the surface might resemble the silhouette of a turtle or seal, the image of which might trigger an initial strike whilst the shark still has the element of surprise. Again this is consistent with most attacks consisting of only a single bite; upon realisation of the mistake the shark moves elsewhere. However, mistaken identity is likely more of an issue in areas of poor visibility, such in estuaries, as opposed to the clear waters of the Red Sea.

It is also possible that sharks that attack people might be acting in a defensive manner. Some sharks display aggression when approached in apparent defence of their personal space, which can be particularly pronounced if the shark feels vulnerable (e.g. if the reef limits its options to move away, or indeed if it might be pregnant).

It is often suggested that feeding of sharks may condition them to associate people with food and thereby increase the risk of attack. Whilst the feeding of sharks in Egyptian waters is illegal, there are unconfirmed reports that it still takes place to please paying guests. But the issue is more complicated than it might seem, since, for example, what cues sharks may associate with the baiting depends very much on how it’s being performed and the species involved. For instance, a study from Seal Island, False Bay demonstrated that sharks responded less, and some altogether, to boats conducting baiting and chumming if they obtained only few food rewards, even though the sharks were still recorded in the area by under water monitors. This demonstrates that in this instance white sharks often ignore these chumming conditions.

In addition, some studies have suggested that the effects of baiting are localised within a small area where the activities are performed, indicating that for safety reasons and as a precautionary approach controlled baiting of sharks should only be conducted where normal recreational diving or snorkeling does not take place. Nonetheless, given that baiting of sharks in the Red Sea is infrequent at best and any influence is likely to be localised, feeding of sharks in the area is unlikely to have played a significant role in encouraging these attacks.

Why so close to shore?

Although open water sharks do on occasion come near the shore, it has been suggested that something may have changed to prompt a sudden concentration of attacks such as these off Sharm. One theory is that a depletion of open water fish stocks from overfishing may be driving sharks elsewhere in search of prey, including near inshore reefs. At present this seems unlikely to be the sole reason, since it has been demonstrated that sharks adopt search strategies to maximise their encounter rates with natural prey distributions, and so the sharks tend to go where their natural prey does.

It is possible, however, given their opportunistic nature that some sharks may have been drawn in from their normal range by an unusual abundance of food availability in the area. At least a day before the first attack, there were reports of livestock carcasses floating at sea and washing up on beaches, discarded at sea having died aboard a vessel transporting cattle and sheep for sacrifice during the festival of Eid al-Adha last month. The presence of these carcasses, drifting in from deeper water, provides a feasible (but unconfirmed) explanation both to why the sharks might be spending more time inshore than usual and why these attacks have been happening at this particular time: curious, opportunistic sharks drawn in to the shallows by the scent of carrion. If this were the case, it might be indicative more of an isolated series of events as opposed to signs of long term change.

Why are sharks important?

Oceanic whitetips used to be one of the most abundant shark species in the oceans, but data suggest that through overexploitation some of their populations have experienced declines in excess of 99%. Sharks are top predators and play a vital role in maintaining balance in the marine ecosystems on which we all rely as a source of food, income and even oxygen. Their removal can trigger unpredictable trophic cascades that can negatively impact entire marine ecosystems, as well as the communities that depend on them. To find out more about why sharks are important, be sure to visit our page on Predator Loss.