Reposted from http://southernfriedscience.com/2009/05/10/four-things-everyone-needs-to-know-about-sharks/
Four things EVERYONE needs to know about sharks
While I could talk forever about why sharks matter (I am, as frequent readers know, literally writing a book about the topic), there are a few things that I would like for everyone to know. I do mean EVERYONE. I know that my blog posts reach a pretty small percentage of the world’s population, but some of you guys are pretty passionate about protecting the oceans. Please tell a friend. Please tell your parents. Please tell your children. Please tell your teachers, please tell your students, please tell your classmates. You get the idea… I really would like for EVERYONE to know these few important facts about sharks. I fervently believe that sharks are threatened today because the majority of the world doesn’t know that they are important, and not because the majority of the world wishes them ill, and that public education on a massive scale is key to saving these animals. I can’t do it without you.
1) Sharks do not represent a serious threat to human beings. Yes, some people have died as a result of shark encounters, and any human death is a tragedy, but it is important to keep in mind the relative risk of a shark attack. Of the over 500 species of sharks worldwide, fewer than a dozen have ever been known to kill a human. In an average year, over 650,000 Americans die as a result of heart disease, giving me a 1 in 5 chance of dying of heart disease in my lifetime. In an average year, over 550,000 Americans die from cancer, giving me a 1 in 7 chance of dying from cancer in my lifetime. In an average year, over 40,000 Americans die in car accidents, giving me a 1 in 84 chance of dying in a car accident in my lifetime. In an average year, 1 American dies from a shark attack, giving me a 1 in 3,748,067 chance of dying from a shark attack in my lifetime.
Again, any human death is a tragedy, but when you have a 1 in 5 chance of dying from heart disease and a 1 in 4 million chance of dying from a shark attack, should we really be so concerned about the threat to us that sharks represent?
Millions of Americans spend time in the oceans each year. Sharks have been evolving incredible sensory systems, part of what makes them such incredible hunters, for over 400 million years. They can also swim a great deal faster than we can. If they wanted to attack humans, a lot more than one American a year would be killed by a shark. Sharks are simply not a serious threat to us.
2) Sharks are important to the health of the oceans. Without them, many ocean ecosystems, including several that are vital to the economy, are in danger of collapsing. This collapse would have devastating ecological and economic consequences… and some of these consequences have already started to happen. In addition to providing natural selection pressure and allowing only the fittest to survive by preying upon the weakest, sickest, and smallest fish, sharks are also important to marine ecosystems in other ways.
In the Outer Banks of North Carolina, tiger shark populations have declined over 97% since 1972. One of their prey items, the cownose ray, has skyrocketed in population without tiger sharks to eat them. These cownose rays eat scallops… and with so many more rays, the scallop population of the Outer Banks has all but collapsed. This is bad news not only for the numerous other organisms that eat scallops, but also for the thousands of people who used to work as scallop fisherman.
A similar event took place in Tasmania. Massive declines in shark populations led to an increase in octopus populations, since there are so many fewer sharks preying on them. These octopus eat, among other things, Tasmanian rock lobsters. The Tasmanian rock lobster fishery is now almost completely gone.
A more complex shark decline related ecosystem destabilization, this one taking place in coral reefs, has led to a decrease in algae-grazing parrotfish populations… and a huge increase in algae. Algae in the Caribbean is starting to take over reefs, killing coral. Coral reefs are home to thousands of unique species of fish and invertebrates, and they generate billions in ecotourism dollars worldwide. This algae takeover is one of the biggest threats facing coral reefs, and food chain destabilization as a result of shark population declines is one of the biggest causes of algae takeover. Losses of sharks are directly related to the destruction of coral reefs.
3) Sharks are in serious trouble. Many shark species have declined in population over 90% in the last 25 years.
Bycatch is one of the biggest threats facing sharks. While fishing for other species, sharks are caught by accident and are killed.
Another major threat facing sharks is finning. Sharks of many species are caught, their fins are cut off, and the still-living rest of the shark (far less valuable than the fin) is dumped overboard to bleed to death or drown. This brutal and unsustainable practice provides material for shark fin soup, a Chinese delicacy associated with celebration. The fins, which are made of cartilage, add absolutely no flavor or nutritional value whatsoever to the soup. By some estimates, over 100 million sharks a year are killed for their fins.
4)Human beings are better off with sharks than we are without sharks, and we are in danger of losing them forever… but you can help! The absolute most important thing that you can do to help, you are already doing just by reading this. Learn all you can about sharks, their ecological and economic importance, and the threats they face. Pass on what you have learned to others. Public education will help far more sharks than these guys ever will. The more people that know about this, the better off sharks will be!
All photographs of and by the author