The Ecological Importance of Sharks

Sharks are often portrayed as fearsome predators, but they play a vital role in maintaining healthy marine ecosystems. As apex predators, sharks are at the top of the food chain and help to regulate the populations of other marine species.

One of the most important roles that sharks play in marine ecosystems is controlling the populations of other predators, such as smaller sharks and marine mammals. By preying on these animals, sharks help to prevent them from overexploiting their own prey species, which can have cascading effects on entire marine ecosystems.

Sharks also play a crucial role in regulating the populations of mesopredators, which are smaller predators that feed on smaller prey species. By controlling the populations of mesopredators, sharks help to prevent these species from becoming too abundant and causing imbalances in the ecosystem.

In addition to their role as predators, sharks also help to maintain healthy marine ecosystems through their role as scavengers. By feeding on dead and dying animals, sharks help to remove these carcasses from the ecosystem, which can help to prevent the spread of disease and other negative impacts on the ecosystem.

Sharks also play a role in nutrient cycling in marine ecosystems. By consuming prey species and excreting waste products, sharks help to recycle nutrients back into the ecosystem, which can help to support the growth of other marine organisms.

Finally, sharks play a crucial role in maintaining the health of coral reefs, which are one of the most important ecosystems in the world. By controlling the populations of herbivorous fish that graze on coral, sharks help to prevent these fish from overgrazing and damaging the coral. This, in turn, helps to maintain the structural integrity of the reef and the diverse ecosystem it supports.

In conclusion, sharks play a vital role in maintaining healthy marine ecosystems. As apex predators, they help to control the populations of other predators and mesopredators, regulate nutrient cycling, and maintain the health of important ecosystems such as coral reefs. By recognizing the ecological importance of sharks and working to protect them, we can help to ensure the long-term health of our oceans and the many species that rely on them.

References:

Ferretti, F., et al. "Ecological role of sharks in a changing world." Advances in Marine Biology 78 (2017): 201-257.

Heithaus, M. R., et al. "Top predators as ecological engineers: effects of mesopredator control on coral reef structural dynamics." Ecology 87.12 (2006): 3460-3468.

Worm, B., et al. "Global patterns of predator diversity in the open oceans." Science 309.5739 (2005): 1365-1369.

Modern Shark Myths

When taking people into sharks’ natural habitat, many of whom for the first time, the One Ocean Diving crew tends to hear misconceptions about these animals daily.

“I think the most common misconception is that ‘If I’m out surfing a shark is going to eat me,’” said Mariah Meyer, a shark safety diver, “which is not not true, but the likelihood of that happening is so slim.”

At the One Ocean office, most of the initial customer questions fall into this category. What is the safety record? How often do people get bit?

The answer is simple. 100%--no one has ever gotten bit. A lot of that has to do with the extensive training the divers go through. But also, no shark is the mindless killer many seem to think they are.

In fact, sharks are aware predators that are constantly searching for other aware predators in the water. It’s hard to ambush something that is focused and combative. Sharks are seeking to maintain their social hierarchy and have learned how to spot potential threats to it. Sharks can hear a bird splash on the surface a mile away and can see about as far as humans. So, posture, focus, and behavior in the water will alter how sharks behave around you.

Shark culling efforts globally—wiping whole populations of sharks so more people are comfortable in certain areas—implies that some people think they would be safer if sharks didn’t exist.

This is simply not true. Sharks maintain healthy fish populations by eliminating the slow, weak, and sick of the school. Since 70% of the earth’s oxygen comes from the sea, sharks are vital in keeping ecosystems across the globe healthy which in turn benefits humans’ overall well-being.

While shark attack statistics are a constant regurgitant, it seems news stories sensationalizing attacks gain much more retention. People are less likely to die from a shark than by not only a dolphin, but also their pet dog, significant other, the car ride to their shark dive, the boat ride out of the harbor, or two lightning strikes.

“You’re more likely to die from a coconut hitting you on the head then to get bit by a shark,” Mariah said, “which is crazy.”

While less than ten people are killed by sharks annually, the recorded number for shark deaths by humans is 100,000,000. Assuming most shark deaths occur off any census, this could put the actual number well over 200,000,000.

The main reason for this is shark fin soup, but bycatch and culling, as well as other shark products, play a major part as well. Shark meat can be found in many brands of pet food. Squalene, shark liver oil, lives in many cosmetic products.

Sharks are much more often killed than discovered dead. So, that shark-tooth necklace you found in the gift shop? If it’s white, the shark was likely killed for its teeth. If it’s brown, or fossilized, it was likely found.

Another often-heard misnomer is that human blood gives sharks cravings, and they can smell a drop from miles away. In truth, they can smell it in about an Olympic-sized pool, still pretty impressive, and it does not make them want to eat people.

A common analogy One Ocean divers use is to imagine walking down the street and catching the scent of a food vendor. It will likely make you hungry. But if you enter a Bath & Body Works, you will smell perfume or scented lotion, maybe even find it pleasant, but you won’t crave drinking it.

Finally, there must be plenty of sharks, right? Well, if the shark-death statistics didn’t already spoil this one, no.

The Marine Mammal Protection Act was established in 1972 to prevent marine mammal species from declining beyond the point where they ceased to be a significant functioning element of the ecosystems they take part in. Since it was enacted, no marine mammal species has gone extinct in U.S. waters. The act has also stopped the decline of many marine mammal populations and have led to the recovery of several, such as humpback whales, gray whales, gray seals, and California sea lions.

Unfortunately, there is no such widespread protection for sharks. Since 1972, the general population of sharks globally has dropped by up to 90%, putting many individual species on endangered lists.

Being aware (as if you are in the water with sharks) of what you are purchasing can make all the difference. Buying fish from a local market as opposed to commercial fisheries, avoiding shark products in general, and also—swimming with sharks! Supporting a shark tourist industry proves even greater value to their presence in some areas.

Take it from someone who swims with sharks every day:

“People tell me that I’m going to get bit by a shark and die, which, first of all, is terrible thing to say to someone, so please don’t say that to people,” Mariah said. “Second of all, if the shark wanted to kill me, it would. If it wanted to bite me, it would. But they don’t. I am continuously in the water with these animals day after day, and have been 100% safe.”

Declining Shark Populations

Sharks have been swimming in the oceans for more than 400 million years, but in recent decades their populations have declined dramatically. Since the 1970s, some populations by more than 90%.

There are a number of factors that have contributed to this, including overfishing, habitat loss, climate change, and bycatch.

Overfishing is one of the biggest threats facing shark populations. Sharks are highly valued for their meat, fins, and other products, and are targeted by commercial fishing operations around the world. The practice of shark finning, which involves removing the fins and discarding the rest of the shark, has had a particularly devastating impact on shark populations.

Habitat loss is also a significant factor. Many shark species rely on specific habitats, such as coral reefs, seagrass beds, and estuaries for feeding, breeding, and resting. These habitats have been degraded and destroyed by human activities such as coastal development, pollution, and climate change.

Climate change is another major threat. Rising sea temperatures and ocean acidification can have a range of negative impacts on marine ecosystems, including changes in the distribution and abundance of key prey species. This can lead to reduced food availability for sharks and other predators, which can ultimately impact their survival and reproductive success.

Bycatch, the accidental capture of non-target species in fishing gear, is also a major issue. Sharks are often caught as bycatch in a variety of fishing operations, including longlining and gillnetting. This can have a significant impact on shark populations, particularly for species that are already vulnerable due to other threats.

Despite the many challenges, there is still hope for conservation. Efforts to reduce overfishing and regulate the shark fin trade have gained momentum in recent years, and a number of countries have implemented measures to protect shark populations. Additionally, habitat restoration and conservation initiatives can help to create more suitable habitats for sharks and other marine organisms.

By raising awareness of the threats facing sharks and taking action to protect their habitats and reduce overfishing and bycatch, we can work toward securing a brighter future for these iconic and important species.

References:

Dulvy, N. K., et al. "Extinction risk and conservation of the world's sharks and rays." Elife 3 (2014): e00590.

Baum, J. K., et al. "Collapse and conservation of shark populations in the Northwest Atlantic." Science 299.5605 (2003): 389-392.

Worm, B., et al. "Global catches, exploitation rates, and rebuilding options for sharks." Marine Policy 40 (2013): 194-204.