In “Ocean Soul,” world-renowned National Geographic photographer Brian Skerry says, “It’s been said that sharks have remained unchanged for hundreds of millions of years because they are perfect and that no further evolutionary change is necessary.”
Sharks have certainly reached the top of the food chain as the ocean’s apex predators. Apex is a word of Latin origin meaning peak or tip. In ecological terms, apex is used to describe an animal that has no natural predator within its ecosystem—terrestrial examples include wolves and cougars.
Although humans might find them terrifying, apex predators are crucial for maintaining healthy ecosystems. Sharks, for example, play a vital role in balancing ocean food webs. They aid in population control of smaller predators, so that prey species are able to exist at healthy levels. They also regulate the behavior and abundance of prey species, protecting habitat like seagrass beds and coral reefs from overgrazing, and promote biodiversity by preventing any single prey species from monopolizing resources.
Sharks also tend to prey on weak or sick members of a species, so as to minimize their caloric hunting expense. This natural tendency towards efficiency promotes healthier populations by advancing the transmission of strong genes, as weaker genes are taken out of the gene pool.
Despite the enormous amount of good we know sharks do for ocean ecosystems, humans hunt sharks for their meat, especially their fins. Sharks can also become collateral damage to commercial fishing for other species—accidental net entanglements or hooking often prove lethal. According to a 2013 report published in “Marine Policy,” humans killed approximately 100 million sharks in 2000, and 97 million in 2010. Annually, humans kill between 63 and 273 million sharks.
What happens when the oceans begin to feel the loss of sharks? Populations of smaller predator species boom, stressing habitats and depleting populations of prey species. These changes can be very detrimental to the fishing industry. For example, depleted great white shark populations have been linked to the boom in gray seal numbers in New England, and the voracious appetite of the seals may be harming the recovery of overfished cod. In North Carolina, a decline in large sharks because of overfishing led to an increase in cownose rays, one of the sharks’ prey species. Cownose rays eat shellfish, and so an increase in their population caused the bay scallop fishery to collapse.
Clearly, apex predators like sharks are absolutely critical to maintaining healthy marine ecosystems. The role of apex predators is better understood today than ever before, and now that we know how vital their role is, it is time to protect and respect the ocean’s top predators.