Today’s society is more educated about sharks and shark behavior than our forefathers. In the 18th, 19th, and much of the 20th century we thought of sharks as mindless eating machines – consuming anything available. Whalers would witness sharks consuming carcasses, as did many other fishermen. Sailors noted sharks following the smaller boats across the ocean, always present when bad situations occurred.
During World War II the U.S. Navy was moving across the Pacific and a deeper understanding of sharks was needed to keep servicemen safe. The sinking of the USS Indianapolis pushed the Navy into a larger research program to determine how to repel sharks and better understand what made them tick. After the war funding for such research continued. One of the leading researchers was Dr. Eugene Clark, who eventually founded the Mote Marine Laboratory in Sarasota with the intention of developing a better understanding of shark behavior. Dr. Clark frequently appeared on the Undersea World of Jacques Cousteau educating the public about how sharks function and respond to their environment. All with the idea of how to better reduce negative shark encounters.
In the 1970s Peter Benchley wrote Jaws but included a marine biologist as one of the key characters who would provide science insight into how sharks work. The film was a cultural phenomenon. I remember standing in a line that wrapped the cinema twice to get in. This was followed by more funding for shark research and a better understanding of how they work. This was then followed by a popular summer series known as “Shark Week”, which remains popular to this day. Many of the old tales of shark behavior were disproved or explained. The idea of a mindless eating machine was replaced with a fish that actually thinks and responds to certain cues. People began to realize that shark attacks are quite rare and could be explained if we understood what happened leading up to the attack.
We now understand that sharks are fish, in a class where the members have cartilaginous skeletons (they lack true bone). They are one of the most perceptive creatures in the ocean, using their senses to detect potential prey and that there are signals that can “turn them on”. On the side of their bodies there is a line of small gelatinous cells that can detect slight vibrations in the ocean – from up to a mile away. The ocean is a noisy place, and it appears that sharks respond to different frequencies. I like to use the analogy of yourself being in a large student cafeteria. Everyone is talking and it is very noisy. Then someone calls your name. Somehow, amongst all the background clatter, you hear this and respond to it. Studies suggest that sharks do the same. With all of the noise moving though the ocean, sharks hear things that catch their attention and then move towards the source.
Blacktip sharks are one of the smaller sharks in our area reaching a length of 59 inches. They are known to leap from the water. Photo: Florida Sea Grant
As they get closer their sense of smell kicks in. Everyone has heard that sharks can detect small amounts of blood in large amounts of seawater – remember “Bruce” from Finding Nemo? It is true, but they do have to be down current to pick up the scent and they will now focus their search to find the source. Some studies suggest other “odors”, such as the urine of seals, might produce the same reaction that blood does. All may lead to shark to think a possible meal is nearby.
Eyesight is not great with any creature in the sea. Light does not travel well in water – but sharks do have eyes and they do see well (one of the old tales science disproved – that sharks are basically “blind”). However, because of the low light, they do have to be close to the target to get a visual. Some studies suggest that sharks are detecting shadows or shapes they may confuse as a potential prey, bite it, and then release when they discover it was not what they thought it was. This idea is supported by the fact that many who are bitten experience what is called “bite and release” – and they turn and swim away. It is also known that sharks have structures in the back of their retinas that act as mirrors, collecting what light is available, reflecting it within the eye, and illuminating their world. They believe they see pretty well at night – better than us for sure. The image they see may appear to be a prey item and may be what is producing the vibrations and odors that they detected.
The Scalloped Hammerhead is one of five species of hammerheads in the Gulf. It is commonly found in the bays. Photo: Florida Sea Grant
And they have one more “sixth sense” – the ability to detect weak electric fields. The shark’s mouth is not in position to attack prey as they move forward. It is on the bottom of their head and, one of the old tales, was that sharks must swim over their prey to bite it. Video taken during the filming for Jaws showed that the shape of the shark’s head changes at the last moment of an attack. The entire head becomes distorted to get the mouth in the correct position for the bite. The “eyes roll back” – as the old fishermen used to say – and the jaws move up and forward. At this point the shark can no longer use its eyes to zero in on the target. However, they have small cells around their snout called the Ampullae of Lorenzini that can detect the small electric fields produced by muscle movement – even the prey’s heartbeat – and know where they are. But – they must be very close to the prey to detect this.
Understanding all of this gives scientists, and the public, a better idea of how sharks work. What “turns them on” and how/when they will select prey. One thing that has come from all of this is that we do not seem to be high on their target list.
The Great White shark. Photo: UF IFAS
The International Shark Attack File is kept at the Florida Museum of Natural History in Gainesville. It has cataloged shark attacks from around the world dating back to 1580. The File only catalogs UNPROVOKED attacks. With provoked attacks – those occurring while people are grabbing them, or fishing for them, or in some way provoked an attack – we understand why the shark bit the human. It is the unprovoked attacks that are of more interest. Those where the person was not doing anything intentionally to invite a shark bite, but it happened.
One thing we can tell from this data is that unprovoked attacks are not common. Since 1580, they have logged 3,403 unprovoked shark attacks worldwide. Considering how many people have swum in the ocean since 1580, this is a very small number. Note, the File is only as good as the reports it gets. In the past, many unprovoked attacks were not reported. But in our modern age of communication, it is rare that such an attack does not make the headlines today.
The Bull Shark is considered one of the more dangerous sharks in the Gulf. This fish can enter freshwater but rarely swims far upstream. Photo: Florida Sea Grant
Of these attacks 1,640 (48%) have occurred in the United States, followed by 706 in Australia. Many have explained this by the large levels of water activities people in both countries participate in. In the US Florida leads the way with 928 unprovoked attacks (57%), most of these (351 – 34%) are from Volusia County. This may be due to breakthrough emergency communications with Volusia County and thus more reports. Many of the reports are minor, small bites from small sharks such as blacktips, but unprovoked none the less. There are 26 unprovoked attacks logged from the Florida panhandle – 3% of the state total – and most of these (n=9) were from Bay County.
When looking at what people were doing when attacked, most were at the surface and participating in some surface water activity such as surfing, skiing, boogie boarding, etc. This is followed by surface swimming or snorkeling.
This brings us to the attacks this summer in the panhandle. There have been a lot of questions as to what may have caused them. They are still assessing the situation before and during these attacks to try and determine why they happened. As we have mentioned, we have learned a lot about sharks and shark behaviors over the last 50 years and several hypotheses are open for discussion. We will see what the investigators learn. Until then, the International Shark Attack File does offer a page on how you can reduce your risk. There is “Advice to Swimmers”, “Advice to Divers”, “Color of Apparel”, “Menstruation and Sharks”, “Quick Tips”, “Advice to Spearfishers”, and “How to Avoid a Shark Attack”. Read more on these tips at https://www.floridamuseum.ufl.edu/shark-attacks/reduce-risk/.
This is not a word that most visitors to the beach want to hear. However, shark attacks are actually not that common and the risk is very low. People hear this every year on shark programs, but it does not seem to make them feel any better. Here is what the International Shark Attack File says (as of 2020)…
–Since the year 1580 there have been 3164 unprovoked shark attacks around the world.
Let that sink in for a moment… 3000 unprovoked attacks on humans in the last 440 years.
Now consider the number of car accident victims that have occurred in the last month within the United States. See what they are getting at? Let’s look at more…
–Of the 3164 reported unprovoked attacks (yes… these data only include what was reported) 1483 were from the United States… 47% of them. This may be due to the fact we are “water people”. The other top countries are Australia, South Africa, and Brazil, all “water people” as well.
–Of the 3164 reports 851 were from Florida (27%). This is the number of reported shark attacks in our state since the Spanish settled it. This comes out to 2 each year – though the data shows a sharp increase in attacks starting in the 1970s (most have occurred since then).
–Of the 3164 reports 25 were from the panhandle region (0.8%) and 7 from the Pensacola Bay area (0.2%).
Let that sink in for a moment. Seven reported attacks from the Pensacola Beach area since the time DeLuna landed here in 1559… 7.
And lets once again consider the number of vehicle accidents that will occur in the bay area today.
These numbers have been posted before. Yet people are still very worried when the hear sharks are in the Pensacola Beach region. When attacks occur, they are big news. The International Shark Attack File does give trends and suggestions on what to do. But as many say, sharks are the least of your worries when you are planning a day at the beach.
Now that we have said all of that, they are truly amazing animals.
They are fish but differ in that their skeletons lack hard calcified bone – they are cartilaginous. There are 25 species in 9 different families in the Gulf of Mexico. Many are completely harmless – 13 of the 25 have been reported to have had unprovoked attacks somewhere around the world – the white, tiger, and bull sharks leading the way. Several rarely come close to shore.
Sharks lack a swim bladder and thus cannot “float” in the water column the way your aquarium fish do. Some, like the nurse and angel sharks, rest on the bottom. Others, like the white and blue sharks, swim constantly to get water flowing over their gills.
Because of this, they are very streamlined with reduce scales. They actually have modified teeth for scales – called placoid scales. Their fins are angular and rigid (as are other open water fish) and some can swim quite fast – makos have been clocked at over 30 mph for short distances. Many have seen video of large white sharks exploding with a burst of speed on a sea lion and actually leaping out of the water with it.
Many species do lay eggs, but others keep the eggs within and give live birth after they hatch. One species, the sand tiger, produce four embryos within the mother. The first to hatch consumes the other three!
The teeth of sharks are famous. Rows of them, some pointed, some are serrated, all are designed to cut and swallow. The tiger shark has a serrated tooth that is angled like a can opener. They can use this to “open” sea turtle shells – adding them to their rather large menu. They “shed” these frequently – placing a new sharp tooth where the dull old one was – and will go through tens of thousands of teeth in a lifetime.
The sensory system is one of the most amazing in the world. Tiny gelatinous cells along their sides, called the lateral line, detect pressure waves from great distances. Splashing, thrashing movements made by fish can be detected a mile away – and get their attention. As they approach the sound their sense of smell kicks in. It has been said that a shark can detect one drop of blood in thousands of gallons of water – and it is true. However, the sharks must be down current of the victim to detect it. Their eyes are much better than most think. They have “crystals” within their retina that act as mirrors reflecting light that enters. Imagine turning on a flashlight in a dark room. Now imagine doing this if the walls and ceiling were mirrors – you kind of understand how they can actually see pretty well even in the low light. That said, light does not travel well under water, so they rely on their other senses more. And as if that were not enough. They have small gelatinous cells around the head region that can detect small electric fields. When a shark bites, it must close its eyes and – as the fishermen say – “roll back” out of the head. At this point the shark is basically blind and cannot see the target it is trying to bite. However, if you move out of the way, the weak electric fields produced by your muscles in doing so can be detected by these cells and the shark knows where you are.
Cool – and scary at the same time. Let’s meet a few of these amazing fish in our area.
The nurse shark. Notice the barbels (whiskers) on its head. Photo: NOAA
NurseShark
This is one of the bottom dwelling sharks that appear harmless – and they are – but if provoked, they will bite. They have less angular fins, or a brownish-bronze color, and really like structure – they are found on our reefs. They posses a “whisker-like” structure called a barbel. These are common on other bottom fish, like catfish, and possess chemo-sensory cells to detect prey buried in the sand. They are not as common here as they are in the Keys, but they have been seen. They can reach lengths of 14 feet.
Blacktip sharks are one of the smaller sharks in our area reaching a length of 59 inches. They are known to leap from the water. Photo: Florida Sea Grant
Blacktip – Spinner
These are grouped together because (a) they resemble each other, and (b) they are both common here.
They are both stream-lined in shape and have blacktips on their fins. Actually, spinner sharks have more fins tipped-black than the blacktip. The anal fin of the spinner is tipped black, but this is not the case for the blacktip. The spinner gets its name from the habit of leaping from the water and spinning very fast as it does so. Both are quite common in the Gulf and the bay. They reach about eight feet in length and unprovoked attacks are very rare.
The Scalloped Hammerhead is one of five species of hammerheads in the Gulf. It is commonly found in the bays. Photo: Florida Sea Grant
Hammerheads
This is a creepy group – check out the head. It is one that many people fear, and unprovoked attacks have occurred. The reader may not know that there are more than one kind – five species actually. They have a tall dorsal fin which sometimes extends above the water when swimming near the surface – the classic “shark is coming” look. Their heads are aerofoil shaped and there are several possible explanations for this. 1) It is more aerodynamic, making it easier for this ram-jetter to swim, using less energy to do so. 2) It is a battery of sensory cells. By swinging the head back and forth, as they do, it is an advanced radar searching for prey, possibly finding it before other sharks do. There are stories of hammerheads arriving first. 3) It is also believed they use their electric sense to detect buried prey – the shape making this easier to find and expose them. It could very well be that all of these could explain the shape.
This pregnant bull shark has an impressive girth.
Bull Shark
Since the film Jaws the world has turned its attention from solely the white shark – to the bull shark. As you can imagine, it is hard for a shark attack victim to tell you which species bit them – “I don’t know… it was a big gray thing chomping on my leg!” or “It was a great white!” because that is the only one many know. But studies sine the 1970s suggest that the bull shark is an aggressive species and may be responsible for a lot of attacks. Particularly in the estuaries and upper estuaries. Bull sharks are what we call euryhaline – they have tolerance for a wide range of salinities. This shark has been reported in low salinities of the upper estuaries and even into freshwater rivers. One report had them over 100 miles from the coast – they are certainly where the people are.
The extremely long upper lobe of the thresher shark. Image: NOAA
ThresherSharks
These are bizarre looking sharks. Most sharks have what we call a heterocercal tail – different – different meaning the upper lobe of the forked tail is longer than the lower. But the threshers take this to the extreme – the tail can make up almost half of their body length, which can be 20 feet. It is believed that use this extremely long tail to herd and stun baitfish – their favorite prey. They prefer colder waters and records in the Gulf are not common. Those that exist suggest they live offshore and are rarely encountered near beaches. There are no unprovoked attacks reported from this shark.
The massive whale shark. Photo: Florida Museum of Natural History.
WhaleShark
Amazing… heart stopping… what else can you say. Encounters with the largest fish on our planet are rare – but when they do happen you will never forget it – it will be one of the highlights of your life. As the name suggest – these are large sharks, with a mean length of 45 feet but some reporting in at 60 feet. They are easily recognized first by their size, but also their coloration. They are brownish color with beige or white spots in nice rows running across the dorsal side. They swim slowly filtering plankton from the sea – though will occasionally take in a fish. Some reports show them vertical in the water column moving up and down filtering from a school of plankton or tiny fish. They are rarely seen because they tend to dive deeper during the day with the plankton layer – then surfacing at night following the same plankton. They are, unfortunately, sometimes struck by boats while at the surface.
When one thinks of the Emerald Coast, visions of sparkling water, baby-powder beaches, rental houses and high-rises interwoven with seafood and pizza restaurants appear. The coast is dotted with fishing boats, pirate ships and dolphin cruises and the beaches are littered with people. But it is what glides under the water that some people are curious about. “Are there sharks in the water here?” is a question I often get from locals and tourists alike. The answer is yes, sharks call saltwater home.
Sharks evoke a variety of emotions in people. Some folks are fascinated and list shark fishing and diving with a shark on their bucket lists. Others are terrified, convinced that sharks only exist to hunt them and bite them while they take a swim. Unfortunately for the sharks, their appearance plays into this later fear, with sharp teeth, unblinking eyes and sleek bodies. The reality is that most sharks only grow up to three feet in length and eat small shrimp, crabs and shrimp, not humans. But it is true that bull, tiger and great white sharks are all large species that have been known to attack humans.
Of the 540 different species of sharks in the world, there are about twelve that call the Emerald Coast home including Atlantic sharpnose, bonnet head, blacktip, bull, dusky, great white, hammerhead, nurse, mako, sand, spinner, and tiger. They don’t all stick around all year, with some migrating south in the winter, while others migrate north.
Sharks use their seven senses to interpret their environment: smell, sight, sound, pressure, touch, electroreception, and taste. Most shark attacks occur when a human is mistakenly identified as prey. There are some easy measures you can take to reduce the risk.
Swim with others, this may intimidate sharks and allows someone to go for help if a bite occurs.
Remove jewelry as it can look like an attractive shiny fish underwater.
Don’t swim where folks are fishing as bait in the water may attract sharks.
Pay attention to any schools of baitfish in the area that may be attracting sharks.
Do not swim at dusk or dawn when visibility may be poor.
Learn how to identify various shark species
Remember, shark attacks on humans are rare. Reports of stepping on stingrays, jellyfish stings, lightning, dangerous surf conditions and car accidents greatly outnumber the number of shark attacks every year.
The holiday season is a special time for most of us! There are many creatures that live under the sea that represent many of our holiday traditions.
Photo Credit: Fl. Museum Of Natural History, George Burgess
Small cookie cutter sharks are found in very deep water during the day, at night they migrate up the water column to feed. Cookie cutter sharks attract their prey with lighted photophores. Photophores are lighted organs located on the lower part of the shark. Small fish are attached to the glow, larger fish searching for prey get close enough to the shark and the shark bites the prey. The cookie cutter shark has specialized sucking lips that attach to the victim. The shark then spins its body around and leaves a cookie cutter shaped hole in the fish.
Photo credit: Wikimedia Commons
Ribbon Eels are found in the Indio Pacific. They have long slender bodies and move like ribbons in and through the crevices reefs. They eat live fish. To view a YouTube video of ribbon fish feeding, click here.
Photo credit: Chris Verlinde
Jingle shells get their name as a result of their shells that when shaken together make a jingle like sound. Jingle shells can be found along the beaches of NW Florida. The shiny iridescent shell is strong and very attractive. Many shell collectors use the shells to make jewelry and wind chimes.
Jingle shells are bivalves and live attached to hard surfaces, just like oysters.
Jingle shells are filter feeders, meaning water is filtered through their gills for plankton.
Photo credit: Wikimedia commons
Christmas tree worms are Christmas tree shaped worms that form burrows corals. The tentacles, which form the tree-like structures are used for feeding on plankton and to breathe. These plumed creatures are a type of polychaete worm.
Christmas tree worms come in many colors and can be found all over the world. They feed by using their feathery appendages, called radioles to capture phytoplankton that floats by the “feathers.”
Christmas tree worms are easily disturbed and will quickly vanish into their burrows as shadows or larger marine life pass by. They return quickly and continue with their sedimentary lifestyles in the coral.
“Marine snow” falls gently on to a coral-covered shipwreck explored in the Gulf of Mexico in 2012 by the NOAA Ship Okeanos Explorer. Photo Credit NOAA
Marine snow gets its name as a result of the fluffy materials that resemble snow falling from the sky. Marine snow is decaying material from plants and animals that have died in the oceans. Marine snow may also include sand, fecal matter and inorganic dust.
Just like snowflakes, marine snow grows as it floats to the ocean depths. Marine snow is consumed by scavengers that live along the deep-sea floor bottom. Check out the video below showing the beauty of marine snow.
There are many more festive creatures that live in the sea. Have a wonderful Holiday Season!
White Shark (Carcharhinus carcharias). Credit: Florida Sea Grant Stock Photo
From Fear to Fascination: White Sharks in the Florida Panhandle
UF/IFAS Extension – Florida Sea Grant
By Rick O’Connor (Escambia County) and L. Scott Jackson (Bay County)
Recently, I was walking on our local Gulf fishing pier checking fishing line recycle bins. You can’t walk on a Gulf pier without looking over to possibly catch a glimpse of a sea turtle or a shark, and I was not disappointed. It was hard to tell which species of shark but it was about 6 feet in length. It swam south along the edge of the pier and then east to make a large arching circle through the emerald water, past bathers at the surf break, and back to the pier only to swim the pattern again. Onlookers from out-of-town were giggling with delight to see the animal while a couple of local fishermen tried tossing bait at it, but most ignored it and went on with their fishing.
Bob Shipp’s book, Fishes of the Gulf of Mexico, lists 29 species of shark found locally. Most are members of the requiem shark family, such as blacktips and bulls, and hammerheads. Though these sharks are certainly capable of attacking humans, their presence usually does not interrupt water activities. Divers who encounter sharks may be startled at first but rarely do they end their dive or have problems with them. Even in 2005, remembered as the “summer of the shark attack”, few people stopped diving or surfing. Individuals have become educated regarding shark behavior and are not as startled when they see one. However, in 2015 there were several encounters with White Sharks.
Sightings in the Gulf of Mexico are rare but usually occur in the cooler months. Is the increased interaction with White Sharks unusual or something to worry about?
Burgess assured me that White Sharks do occur in the Gulf of Mexico usually during cooler months and are transients, as opposed to residents. Their movement in and out of the Gulf is temperature driven. As late spring Gulf waters continue to warm into early summer, sighting a White Shark is less likely to occur. According to Burgess, White Sharks use deep water when traveling but prefer shallow water when hunting fish, turtles, and marine mammals. So, inshore encounters especially in cooler months would not be unusual.
Why is there a sudden increase in the numbers of encounters?
One part of the answer lies with the increased number of White Sharks. Conservation of sharks has been effective. Additionally, with the passing of the Marine Mammal Protection Act, there are more marine mammals, thus an increase in their predators, White Sharks. The other part is the number of humans visiting the northern Gulf has increased. There are more more visitors to marine waters, especially since the Deepwater Horizon oil spill. Everyone has a camera. Beachgoers, Swimmers, Divers, and Anglers all have improved technology to record their adventures.
Is Northwest Florida a “hot spot” for White Sharks? Burgess indicated that the northern Gulf of Mexico is more productive than the peninsular Florida due to the number of nutrient rich rivers in the region. Seeing more White Sharks here would not be any more unusual than finding more snapper, lionfish, or other species of shark. As far as worrying, there have been no records of White Shark attacks in the northern Gulf of Mexico since they began keeping records in 1872.
Finally, what does one do if they encounter a White Shark?
The quick answer is nothing different than with any other shark. It is true that most White Shark attacks occur at the surface but there are no records of any attacks in Florida. Burgess indicated that the Bull Shark is probably a bigger threat than the White Shark. For more information about Bull Sharks and general tips to avoid a negative shark encounter read this articlehttps://nwdistrict.ifas.ufl.edu/nat/sharktips
In a recent video, recorded near Apalachicola, a diver was on an anchor line on a decompression stop when he saw a White Shark approaching from depth. What should a diver do in this situation? Should they swim for the surface and risk decompression sickness, remain still, or return to the bottom?
The answer has a lot to do with what the shark is actually doing. Is the shark interested in the diver or acting aggressively? Burgess suggests, you assess the situation and the shark’s behavior. All options are on the table and have to be weighed against the consequences given in this scenario. As a last resort, a diver may need to make a quick but graceful exit out of the water, past the shark, and depend on their diving partners to render aid as needed. The lesson is for divers to be prepared for a variety of potential issues on every dive.
