There are more than 500 species of sharks swimming in the world’s ocean. Yet when most people think of these cartilaginous fish, a single image comes to mind: a large, sharp-toothed and scary beast. That generalization does sharks a huge disservice, as they have far more variety than that. They range in size from the length of a human hand to more than 39 feet (12 meters) long; half of all shark species are less than one meter (or about 3 feet) long. They come in a variety of colors (including bubble gum pink), and some feed on tiny plankton while others prefer larger fish and squids. They are found in just about every kind of ocean habitat, including the deep sea, open ocean, coral reefs, and under the Arctic ice.
Wherever they live, sharks play an important role in ocean ecosystems—especially the larger species that are more “scary” to people. Sharks and their relatives were the first vertebrate predators, and their prowess, honed over millions of years of evolution, allows them to hunt as top predators and keep ecosystems in balance.
But sharks are in trouble around the world. Rising demand for shark fins to make shark fin soup, an Asian delicacy, has resulted in increased shark fishing worldwide; an estimated 100 million sharks are killed by fisheries every year. Sharks are accidentally caught in nets or on long line fishing gear. And because of needless fear spurred on by films such as Jaws, the instinct for some is to hurt or kill sharks that come near—such as the controversial shark culling in Australia. (This is despite the fact that you are more likely to be killed by a lightning strike than bitten by a shark, and more likely to be killed by a dog attack than a shark attack.) Combined, these actions have decreased many shark populations by 90 percent since large-scale fishing began.
All of this puts these incredible animals—and the ecosystems in which they play a role—in jeopardy. To protect them, communities and companies around the world are enacting science-based fisheries management policies, setting up shark sanctuaries, and banning the practice of shark finning and the trade of shark fins.
@WhySharksMatter - Twitter account from David Shiffman, marine biologist studying shark feeding ecology and conservation.
Shark management in the U.S. - an overview from the National Oceanic and Atmospheric Administration (NOAA)
The Conservation Status of Pelagic Sharks and Rays: Report of the IUCN Shark Specialist Group Pelagic Shark Red List Workshop (PDF)
Global Status of Oceanic Pelagic Sharks and Rays: A Summary of New Scientific Analysis from the Lenfest Ocean Program (PDF)
Sea Monsters: Prehistoric Creatures of the Deep by Michael J. Everhart
Demon Fish: Travels Through the Hidden World of Sharks by Juliet Eilperin
Sharks of the World (Princeton Field Guides) by Leonard Compagno, Marc Dando and Sarah Fowler
Patterns and ecosystem consequences of shark declines in the ocean - Francesco Ferretti, Boris Worm, Gregory L. Britten, Michael R. Heithaus and Heike K. Lotze
Vision in elasmobranchs and their relatives: 21st century advances - Tom Lisney, et al. (subscriction required)
Long-term change in a meso-predator community in response to prolonged and heterogeneous human impact - Francesco Ferretti, Giacomo C. Osio, Chris J. Jenkins, Andrew A. Rosenberg & Heike K. Lotze
Cascading top-down effects of changing oceanic predator abundances - Julia K. Baum and Boris Worm (PDF)