All about sharks

It’s that time of year again, when the Discovery Channel reels us back in for Shark Week. At a time when everyone has sharks on their minds, we thought we’d provide 7 NSF-supported discoveries about some of the ocean’s best-known predators.

Credit: Wikimedia Commons

1. Sharks don’t hunt humans. Most shark bites happen because typical shark prey is close to shore, where people are swimming. The majority of bites are investigatory bites that involve the shark releasing the person, then swimming away. Sharks sense and experiment with their mouths.

2. Sharks follow their food. Water temperature, food supply and, occasionally, reproductive conditions bring sharks closer to shore. Some telltale signs of shark areas include small fish near the surface, or large numbers of seabirds diving into the water to feed. It’s a good idea to stay clear of these areas.

Credit: Kelly VonDrehle, IODP

3. Sharks are the envy of engineers. Sharks are among the oldest living species, with an evolutionary history dating back 400 million years, predating the dinosaurs. During that time, sharks have evolved into the lean machines that they are today. Engineers are fascinated with the qualities of shark skin, made of tiny, V-shaped scales called dermal denticles. They hope to mimic its sleek, drag-reducing qualities. Bioengineered shark skin could be used to improve the performance and agility of aircraft and submarines.

4. They can sense your electric field. Hollywood does a great job showing sharks’ ability to smell blood, but that’s not the only sense these predators use. In addition to smell, sharks rely on vision, feel (using special organs called lateral lines that sense water movement) and electroreception, a sort of “sixth sense” that allows them to detect the electrical fields of living things. Researchers have found that different shark species favor different senses. When one sense is blocked, they switch to another.

5. Great white sharks get old: Male great white sharks live to around 70 years old and females reach about 40 years old. Similar to humans, sharks show their age through physical properties, such as their ear bones and vertebrae. These body parts develop layers of tissue, just like annual growth rings in trees. Scientists use radiocarbon dating to accurately predict age.

Credit: ©J. Sparks, D. Gruber and V. Pieribone

6. Some sharks glow in the dark: Catsharks give off a bright green glow deep underwater. Recent research has shown that these sharks can adjust the amount of light they give off in order to make themselves more visible to neighbors of the same species. By using different cameras that replicate the sharks’ view, researchers have found that they communicate through light variations.

Photo credit: Florida International University

7. They are critically important to the health of the world’s oceans: When factors such as heat waves destroy seagrasses, sharks become critical for ecosystem health. Where sharks rove seagrass beds, dugongs and other shark prey species steer clear. That keeps seagrasses — which grazers like dugongs and other marine animals eat — from being decimated. Without enough sharks, the grazers could devour the underwater grass beds, researchers have found.

Sharks are incredible species. NSF-funded scientists have found that some properties in shark immune systems and skin could provide patterns for how to better protect human immune systems. Their existence not only protects ocean ecosystems but improves human existence.

Unfortunately, shark species are vulnerable to fishing pressures. But while sharks have long lifespans, they are also slow to reproduce, meaning it can take years and even decades for rebuilding the population.

Enjoy Shark Week and remember the important role these species have in marine ecosystems. Behind the jaws these fish really are, “friends, not food.”