How to tell the difference between a shark and a dolphin by their fins
Although shark bites are rare, beach goers trying to savor the last two months of the summer season may feel a little more cautious after an incident on Tybee Island beach last week.
According to experts, sharks can reach the surf area and it is not uncommon to see a dorsal fin sticking out of the water. Sightings increase during the summer, as our vacation season coincides with their migratory patterns, says Bryan Fluech, of Marine Extension and Georgia Sea Grant at the University of Georgia.
“This is their feed zone and this is also where we go in the water,” said Fluech, “[But] statistically there’s a lot more chance of something happening at the beach than, you know, of actually being at the beach. “
But it can be hard to tell if you’ve actually spotted a shark or other marine animal. Here are some tips to know if you are in the presence of a real shark.
Dorsal fin shape
Sharks are most often confused with dolphins, but can usually be distinguished by their distinctive dorsal fins, according to Michelle Passerotti, fish biologist in the Apex Predators program of the National Oceanic and Atmospheric Administration.
“Shark fins generally have a more triangular shape,” Passerotti said. “The leading edge of the dorsal fin may have a small curve depending on the species, but generally the trailing edge of the dorsal fin that points towards the tail is quite square or flat.”
Passerotti said that for all species, most dolphin dorsal fins will be rounded, with sharks having a noticeably straight edge at the tail of their dorsal fins. Although some shark species have rounder fins, like the hammerhead shark, they are still distinct enough to stand out from the beach.
“If you just saw the top of a hammer-shaped dorsal fin sticking out of the water, you might think, oh, it’s got a curve, it might be a dolphin,” Passerotti said. “But it’s also sharper at the end; dolphins tend to be rounded, while being more curved and hook-shaped.”
Caudal fin orientation
If a dorsal fin piercing the surface of the water is accompanied by a smaller caudal fin a few feet behind, that’s another sure sign of a shark sighting, according to Dr. Fred Scharf, professor in the biology department. and Marine Biology from UNCW.
“In the case of sharks, sometimes the tail or caudal fin will also break the surface of the water because they have an upright caudal fin or tail,” Scharf said. “The dolphin’s tail, however, is horizontal, like that of a whale.”
Scharf said the tail fin would not always be visible to the smaller sharks most common on beaches in this region – like black tips and spinners – but would be more visible on larger predators like bull or tiger sharks .
Still, the triangular shaped dorsal fins would provide enough contrast and warning.
“Their fins are going to be bigger, but they’re just the same shape and quite distinct from a dolphin,” Scharf said.
People can also observe the animal’s behavior to find clues about its species. Dolphins are known to swim in small pods while sharks are generally solitary hunters.
“Usually when you see a dolphin you will see more than one,” Scharf said. “Sharks that feed in the surf area will tend to be solitary most of the time. There may be several sharks in the area, but they don’t tend to swim together.”
The way they move can also be a gift, with dolphins constantly having to break the surface to breathe.
“Sharks tend to swim in a constant motion in one direction, you know, they don’t move like dolphins going up and down in a kind of wave motion,” Passerotti said.
“Sharks in this proximity usually forage for food, moving back and forth while chasing something, but they generally won’t have up and down movement in the water.”
Other sea creatures
Some have suggested that recent dorsal fin sightings could have come from a manta ray or even a whale, but experts say this is unlikely.
Manta ray sightings typically involve two fins parallel to each other jutting out of the water, and they would typically be smaller than shark or dolphin fins.
As for whales, Scharf said, while plausible, a whale watching so close to the beach would be hard to confuse with anything else.
“If you’ve ever seen one, you would know,” he said.
Typically, whales would be spotted further from the beach and rather than just noticing a fin, it is likely that their entire body could be seen piercing the surface of the water.
“If it’s a whale, it’s going to spray through its blowhole and it will also tend to be really big,” Passerotti said.
Have you been bitten by a shark?
Although some of the recent attacks have not been confirmed to be from sharks since they have not been seen, Passerotti said it is possible to identify a shark bite by the wounds they leave behind.
“Shark teeth have a very distinct shape and it’s very specific to the species,” she said. “So often times you will get an imprint that will have a distinctive look.”
Earlier this year:Shark bites 7-year-old girl swimming at Ocean Isle Beach
Experts can use tooth pattern, tooth size, overall bite size, and other measurements to determine if you’ve been bitten by a shark and can even narrow down the species.
“If you watch it long enough you can kind of get a feel for what it could be like,” Passerotti said. “And if you are not sure, you better give it up and not try to swim and figure out what it is.”
Journalist John Orona can be reached at 910-343-2327 or [email protected]