SHARKs! Changing Fear to Fascination

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SHARKs! Changing Fear to Fascination

Sat, 08/08/2020 - 10:07
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Article and Photography by ALICE MARY HERDEN and BRITTANY HALL-SCHARF, Marine Agent II UF/IFAS Extension Hernando 

 As the brackish waters from the coastal edge of Hernando County flow ever so smoothly into the salty waters of the Gulf of Mexico, that transitional blend of life turns into an oasis of mysterious creatures. Unfortunately, the fear of what is living in the vast unknown such as sharks gets a bad reputation.

With just one glance of a shark’s sharp teeth, one must assume that these predators are actively searching for their next human meal. Many media sources have embellished this horror, thus furthering the misunderstanding of these fascinating fish.

When asked to name a shark species, many people will quickly proclaim the “Great White Shark!” While images of this white shark are often featured on posters or video trailers, this shark is not an accurate representation of the vast majority of sharks swimming in the world’s oceans, nor is the word “great” even included in its real name.

SHARK EDUCATION

Did you know that there are approximately 540 different species of sharks living in our oceans today? Compared to the 33,000 species of bony fishes, the species diversity of sharks is quite small. Scientists believe that half of the shark species live their entire lives at depths greater than 200 meters. A depth much deeper than any human can swim.

Most species of sharks in the world may only grow up to three feet in length- not nearly the size of the “apex predators” often highlighted on television. Their skeleton is composed of cartilage, a substance much lighter than bone, and they use fatty oils stored in their liver to control where they swim within the water column.

Sharks use specialized organs, called gills, to breathe. As they swim, water passes through the mouth and is forced over the gills. Dissolved oxygen in the water is taken up by tiny vessels and transported around the shark’s body. This process requires many sharks to keep swimming to breathe.

Sharks process their watery world using an array of senses! Seven to be exact.

Sound. Because sound travels through water at a much faster rate than on land, scientists believe this may be one of the first senses a shark applies to detect prey. Sharks use their inner ears to track wounded fish from 800 feet away.

Smell. Although their nares look like human nostrils, sharks do not use them to breathe. By pulling water in through these openings, sharks engage their olfactory senses to process chemical gradients for long-distance navigation and to detect scents produced by prey or potential mates.

Pressure. Using a specialized organ called a lateral line that runs tail to snout, sharks create pressure maps of their surroundings. This sense aids in navigation and allows sharks to detect movements around them.

Sight. Because light does not penetrate the water well, and sharks live at various ocean depths, visual capabilities differ among shark species. Sharks that live in deeper depths also use a reflective layer of cells behind their retina to see in lower-light conditions.

Electroreception. Ampullae of Lorenzini, a complex electro-sensory organ, allows sharks to detect Earth’s magnetic fields, temperature, and muscle contractions in prey. These receptors are located around the mouth and face and are thought to help sharks accurately migrate long distances.

Touch. Sharks do not have hands and fingers to feel what is around them; thus, they are left to use their teeth to explore. Sensory nerves are embedded in the shark’s teeth, mouth, and skin that allow them to experience touch.

Taste. Although sharks do not use their sense of taste to find food, they will often conduct a test bite to determine if something is appetizing. If they decide it is not food, the shark will simply spit out the object. Scientists believe this is why many shark attack victims survive the encounter.

The shape and size of a shark’s jaw and teeth vary by species. Their teeth, composed of calcium phosphate, are arranged in rows along the jaw. When a tooth falls out or becomes worn, a new tooth will rotate forward and take its place. This is why sharks’ teeth are found around the world.

Although shark species traversing today’s ocean waters have gone through millions of years of evolution, their cartilaginous bodies have made documenting evolutionary transformations somewhat difficult. Cartilage degrades rather quickly, leaving only their teeth behind. Scientists study the fossilized teeth and scales, called dermal denticles, to identify and describe sharks of the past.

RESEARCH AND FORENSIC

There are 12 species of sharks commonly found swimming in Hernando’s coastal water. However, when the waters become colder in the winter months, very few species will remain.

“Some sharks, like the blacknose and sharpnose, will migrate offshore during the winter,” said Dr. Dean Grubbs, Associate Director of Research of the Florida State University Coastal and Marine Laboratory in St. Teresa, FL. “Other species will migrate north in the spring and south in the fall. We’ve tracked blacktip and lemon sharks we tagged down in the keys who migrated up to Florida’s panhandle.”

Regardless of their size or how long they hang out in a specific area, sharks fill different roles within an ecosystem throughout their lives. Many sharks swim around our world’s oceans, snacking on small shrimp, fish, and crabs. Even a fierce bull shark feeds on small fish in its juvenile life stage.

“You will often hear sharks referred to as apex predators. Most sharks are not apex predators,” Grubbs explained. “They each feed on a different piece of a very complicated food web, and removing them can destabilize the whole ecosystem. Sharks are a very important piece of the puzzle.”

Sharks are a target for overfishing because they grow slowly, take quite a few years to reach maturity, and have very few offspring. They are also slower to recover once they are overfished. Proper management is vital to the persistence of shark populations, and Grubbs’ lab is dedicated to learning more about different species patrolling the waters off Florida’s coast.

But what about Florida being known as the shark bite capital of the world? You can use a test to figure out if there are sharks in the water around you.

“If you stick your finger in the water and it tastes like salt, there are sharks in the water,” said Grubbs. “Sharks are always out there, and it is rare that one intentionally bites a person along our coastline.”

Grubbs further explained that shark bites in Florida are often driven by large migrations of Blacktip sharks along white sandy beaches. These sharks are hunting for small fish hiding in the murky surf zone. Unfortunately, vast densities of people also populate these coastal areas, and the swimmers forget to remove shiny objects, such as jewelry before they venture out into the water. This contrast may attract a shark, and the swimmer is mistakenly bitten. These encounters often result in minor injuries.

Bull sharks are usually the culprit if a significant injury is involved. They exhibit an exaggerated side-to-side swimming pattern as a warning display when swimmers or boats get to close.

 “Everyone likes sandbars, including sharks and spotted seatrout. These types of habitats funnel schools of fish along the edges making a great place for sharks to find a meal. When a person gets bit by a bull shark, they most likely did not see the warning display made by the shark prior to the attack,” Grubbs said.

Tyler Bowling, Florida Museum of Natural History’s Florida Program for Shark Research’s Program Manager, has been intrigued by sharks since he was two years old.

 “I fell in love with NatGeo programs about the seas, and the sharks were my favorite part. I was just fascinated about all their adaptations and how intricate they were,” Bowling said.

Bowling also contributes to the International Shark Attack File, a comprehensive database of all known shark attacks. (https://www.floridamuseum.ufl.edu/shark-attacks/) His team tracks vital elements, such as location, time of day, and provocation. This collective information helps other marine biologists have a research outlet to understand shark behavior better.

“My personal research, as well as my managerial role (at the Museum), centers a lot around attacks around the world,” Bowling said. “Basically whenever there is a bite, whether it be here in Florida, Australia...we conduct an investigation. We can look at and say, the bites in this area of the world most likely come from this type of shark. This helps us figure out the best safety procedures for that area.”

Across the state on the East Coast of Florida, New Smyrna Beach is a sweet spot for shark bites.

“We get double digits of unprovoked bites there, usually on surfers from small sharks,” Bowling said. “We are trying to figure out what environmental factors bring these sharks in close to shore during the times when people are out surfing.”

Bowling’s research involves understanding how environmental factors may or may not contribute to shark bites. But there is another approach to scientific research; forensics.

Different species of sharks have various forms of teeth, as well as biting behaviors. Some sharks will pull as other species will thrash side to side. Bull, tiger, and white sharks have distinctive bites, but the classic small sharks like blacktips and spinner sharks are somewhat similar in their teeth formations.

“We are getting into identifying shark species based on residual DNA in the bites of people,” Bowling said. “We published a small paper on identifying a shark species from a tooth fragment that was in a victim, and now we are working on saliva residue.”

GETTING UP-CLOSE

While many of us are unable to get up-close and personal with sharks, there is another way to view these amazing creatures of the waters.

Associate Curator, and shark enthusiast Eric Hovland and one of the original marine biologists of the Florida Aquarium, grew up in Wisconsin, surrounded by freshwater. His family often would travel to coastal waters during the summer, and there he formed the term, “Salt in my veins.”

Inspired by Jacques-Yves Cousteau, he pursued his career as a marine biologist.

“It just became ingrained in me that I needed to be by the ocean. I felt that I was in the right place.” Hovland said.

The Florida Aquarium exhibits a few sharks that thrive in our coastal waters. It’s one of the best opportunities to learn about the variety of coastal marine life and the chance to be in a similar environment like that of sharks.

“We have come so far not just myself but also the conservation work we’re doing to protect the coral reefs. To tell great stories about the need to protect our environment, the turtles that we rescued by the hundreds and then another main story and a big pillar of conservation is protecting sharks,” Hovland said. “One of the best ways we do that is to help build their brand and help people better understand. If we help them understand it, that fear can turn into fascination, and that’s how it worked for  me.”

The Shark Swim program at the Florida Aquarium brings you up close to a variety of marine life that many may not experience. These experiences could intrigue younger or even older generations to learn more about shark ecology, research, and conservation efforts.  

“All the sharks are worthy of our protections and understanding, and even the scary ones,” Hovland said.

SAFETY TIPS

Most shark attacks occur when a human is mistakenly identified as prey. However, there are some preventable measures you can take to lessen your chances of a shark encounter.

Buddy System. Sharks may become curious to areas where swimmers are creating a significant amount of movement, such as intensive splashing. Having a buddy system may be intimidating for sharks, and if assistance is needed, help is close by.

Remove jewelry. Underwater, shiny objects look like fish. In fact, artificial lures used by fishermen incorporate flashy materials to mimic wounded fish.

Do not swim where others are fishing. Cut bait may entice sharks to the area.

Pay attention to your surroundings. Schools of baitfish swimming by might be the target of a hungry predator. Sharks also utilize deep cuts along sandbars to hunt and move into coastal areas.

Do not swim at dusk or dawn. Visibility in the water is poor during these times.

Learn how to identify sharks. Some shark species look similar to one another.

Remember, shark attacks on humans are rare. Reports of stepping on stingrays, jellyfish stings, and car accidents greatly outnumber the number of shark attacks every year.

LEARNING MORE

Reeling in a shark can be an exciting adventure. But before you go, know the rules! The National Oceanic Atmospheric Administration and the Florida Fish and Wildlife Conservation Commission have valuable information for those who enjoy shark fishing.

https://www.fisheries.noaa.gov/topic/atlantic-highly-migratory-species

https://myfwc.com/fishing/saltwater/recreational/sharks/

https://learningmyfwc.remote-learner.net/course/view.php?id=40

Visiting museums and aquariums, reading field guides and books, or simply volunteering with a reputable program are all ways to learn more about these fascinating fish. Co-existing with these misunderstood creatures is key. Public knowledge and awareness is an essential stride to ensure the conservation of the world’s oceans and animals who rely on it.

COMMON SHARKS

“Roughly 80% of the shark species we find off Hernando’s coast are the bonnethead, blacktip, and Atlantic sharpnose shark,” Grubbs said.

Bonnethead Shark (Sphyrna tiburo)

Bonnetheads are one of the smaller species of hammerheads and are easily distinguished by their spade-shaped heads. These warm-water coastal sharks migrate with the seasons and are often attractions at aquariums. They primarily feed on crabs and use their oddly-shaped heads like a metal detector to find their food hiding below the sediment. The Ampullae of Lorenzini enable the sharks to sense electromagnetic disturbances given off by the hidden prey.

Atlantic Sharpnose Shark (Rhizoprionodon terraenovae)

The Atlantic sharpnose is extremely abundant in Florida’s coastal waters and often mistakenly referred to as sand sharks. The adults are gray with small, white spots along their sides and fins, and only grow to be three feet long. Atlantic sharpnose sharks love to eat shrimp and fish and are frequently caught by fishermen.  

Blacktip Shark (Carcharhinus limbatus)

Like the Atlantic sharpnose, the blacktip shark is known to leap out of the water when it is caught. Blacktip sharks are one of the larger shark species in the area growing to six feet in length. Because of its black-tipped fins, it is often confused with the spinner shark. However, the anal fin on the blacktip shark does not have the black marking that the spinner shark does. Blacktip sharks like to feed on schools of fish in coastal waters and will occasionally eat other sharks.

Additional species found in Hernando’s waters are the Blacknose shark (Carcharhinus acronotus), Nurse shark (Ginglymostoma cirratum), Tiger shark (Galeocerdo cuvier), Great Hammerhead (Sphyrna mokarran), Scalloped Hammerhead (Sphyrna lewini), Lemon shark (Negaprion brevirostris), Finetooth shark (Carcharhinus isodon), Bull shark (Carcharhinus leucas), and Spinner shark (Carcharhinus brevipinna). To learn more about these sharks, visit:

https://edis.ifas.ufl.edu/sg062

https://www.floridamuseum.ufl.edu/sharks/education-resources/

 

 

 

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