Is Overfishing Giving Sharks a Taste for Humans?
A series of shark attacks in Australia has fueled the fire under an ongoing debate of whether sharks are increasingly targeting humans. The three attacks took place in January within a 24-hour period in areas near Perth, Sydney, and Tasmania.
Worldwide there are probably 70-100 shark attacks annually resulting in about 5-15 deaths, according to ISAF.
"Humans are next in line on the food chain," veteran shark hunter Vic Hislop is quoted as saying in an AFP article. "It will definitely get worse."
But is the spate of attacks really a sign of things to come, or simply a coincidence? The answer depends on who you ask.
"It's certainly a theory that yeah, if you remove the primary source of food then they're [sharks] going to have to find something else to eat and they might penetrate into different environments to find that food," Rachel Robbins from the Rodney Fox Shark Research Foundation told ABC News.
She pointed out that overfishing in South Australian waters may be causing sharks to swim closer to shore, leading to increases in sightings but not necessarily attacks.
On the other hand, Dr. Wayne Sumpton from the Queensland Department of Primary Industries (DPI) had a different opinion about the recent sightings and attacks.
"There's nothing out of the ordinary. The patterns of shark movements and when they're around are basically the same as it's been since we've been looking at it," he told ABC News. "Sharks do move inshore and they do move around a bit but realistically... more fisherman are fishing in close to shore than out deeper so you'd expect them -- if they're responding to fishing - to be moving away from where the fishing is."
Are Sharks Actually the Ones at Risk?
While sharks’ preferred feeding sources are increasingly being targeted by commercial fisheries, so are sharks themselves. Valued for their meat and fins, yet slow to mature (some sharks take 16 years or more), sharks populations are quickly dwindling.
In fact, studies have shown that shark populations in the northwest Atlantic Ocean have declined by an average of 50 percent since the early 1970s. Further, due to overfishing shark populations around the world have declined by 90 percent, and up to 99 percent along the U.S. east coast.
Already, 126 species of shark are on the World Conservation Union’s (IUCN) endangered list.
"Sharks are definitely at the top of the list for marine fishes that could go extinct in our lifetimes," Julia Baum of the Scripps Institution of Oceanography in California and a member of IUCN shark specialist group told The Guardian. "If we carry on the way that we are, we're looking at a really high risk of extinction for some of these shark species within the next few decades."
How Common are Shark Attacks Anyway?
According to the International Shark Attack File (ISAF) from the Florida Museum of Natural History, there have been 2,199 shark attacks worldwide from 1580-2007. Of them, 994 occurred in the United States (including Hawaii), and 53 of them were fatal.
Though any large shark, roughly two meters or longer in total length, is a potential threat to humans, white sharks, tiger sharks and bull sharks are the three species thought to be the primary attackers of humans.
To put this into perspective, ISAF points out that:
You have a 1 in 11.5 million chance of being attacked by a shark
You have a 0 in 264.1 million chance of being killed by a shark
You are more likely to be killed by lightening, a dog attack, riding a bicycle, or in a sand hole collapse than you are to be killed by a shark
Meanwhile, your annual risk of death during your lifetime for being killed by a shark is 1 in 3,748,067. This is much lower than your risk of:
Heart disease: 1 in 5
Hospital infections: 1 in 38
Car accidents 1 in 84
Accidental poisoning: 1 in 193
Falls: 1 in 218
Excessive cold: 1 in 6,045
Sun/heat exposure: 1 in 13,729
Fireworks: 1 in 340,733
So your risk of shark attack is actually very, very small. And as ISAF points out:
As the worldwide human population continues to rise year after year, so does our interest in aquatic recreation. The number of shark attacks in any given year or region is highly influenced by the number of people entering the water.
That said, if you are one of those people enjoying the water, you can reduce your chances of encountering a shark even further with the following tips from ISAF:
- Swim in groups-sharks are most likely to attack a person who's alone.
- Don't swim too far from shore (you're farther away from help and more isolated).
- Don't go in the water at night or during twilight hours when sharks are most active.
- Leave shiny jewelry at home -- a shark could mistake it for shiny fish scales.
- Don't swim in areas used by commercial or sport fisherman where bait is used often (if there are diving seabirds around, it's likely this is the case).
- Don't swim if you have an uneven tan -- sharks don't like tan lines! (seriously, the contrast could attract them).
- The same goes for bright colored clothing -- sharks may be attracted to it.
- Don't splash excessively or swim with pets (who may thrash around and attract a shark).
- Be careful around steep drop-offs or when between sandbars (these are two areas sharks love).
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International Shark Attack File
Yahoo News January 12, 2009
ABC News January 12, 2009
ABC News Australia January 12, 2009
The Guardian February 18, 2008