Sharks hold a special place in the hearts and minds of many people and, more importantly, they keep marine ecological systems healthy by keeping fish populations in check.
But one type of shark found in Florida waters has been suffering in recent years, mostly from overfishing.
Reef sharks numbers are dropping around the world as fishing pressure has increased on this species, according to a new global study published last week.
“People need healthy coral reefs,” said Mike Heithaus, co-author of the study and executive dean of the College of Arts, Sciences and Education at Florida International University. “We are seeing that when sharks disappear, that causes other changes in these ecosystems.”
Reef sharks include grey reef, blacktip reef, whitetip reef, nurse and Caribbean reef sharks.
“Keeping shark populations healthy, or rebuilding them, is important for maintaining their roles for healthy reefs,” Heithaus said.
Collectively, they’ve declined by an average of 63%, according to a five-year study conducted by Mote Marine Laboratory, Florida International University and a handful of international scientists.
“While overfishing and poor governance is associated with the absence of these species, they are still common in places where shark fishing was banned or highly regulated,” said Demian Chapman, director of the shark and ray conservation program at Mote. “Reef sharks can be important for human livelihoods through dive tourism and if very carefully fished. An investment in reef shark conservation can therefore be good for people, too.”
Let’s take a closer look at the five species of reef sharks that have declined in numbers:
Grey reef shark
Considered to be one of the more aggressive shark species, grey reef sharks (Carcharhinus amblyrhynchos) are grey on top and white on the bottom, with a black trailing edge on their tail fins.
Fished commercially for their fins (used in soups), grey reef sharks are also popular with dive operations as they’re easy to find as they’re territorial and generally stay in the same location.
“Grey reef sharks are social, gathering in groups during the day and hunting alone at night,” a University of Florida website reads. “They are inquisitive and commonly approach divers. They are also believed to be territorial and have been documented to arch their backs and push their pectoral fins downward and swim in an exaggerated pattern as part of a territorial display.”
Growing up to 7 feet in length, grey reef sharks have attacked eight humans, with one of those encounters being fatal, according to the International Shark Attack File.
Sharks that eat grey reef sharks include silvertip, tiger and great hammerhead sharks, according to UF.
Blacktip reef shark
Recognized for their black-tipped dorsal fin, blacktip reef sharks (Carcharhinus melanopterus) grow to about 5 feet and are among the most common sharks found across the planet.
Smaller in size than the grey reef shark, blacktip reef sharks are sometimes confused with other species.
“The grey reef shark can be distinguished by its stockier body and lack of black tip on the dorsal fin,” a UF website reads. “The prominent black tips on all fins distinguishes this species from others that it may otherwise be easily confused.”
Blacktip reef sharks show strong “fidelity” to their home reefs, and they rarely travel beyond those areas.
Nurse shark
Historically targeted for their liver oil and hides, nurse sharks (Ginglymostoma cirratum) are considered extinct in their far southern ranges in Brazil.
The species is popular in the Caribbean and in South America as table fare.
Light tan to brown on top, it’s thought that nurse sharks, once grown, don’t have predators chasing them, although their remains have been found in the bellies of lemon and tiger sharks.
Nocturnal sharks that sleep on sandy bottoms or in coral caves, nurse sharks have a powerful, unyielding bite, although they rarely attack humans.
“In some instances, the jaws lock and can only be released using surgical instruments,” a UF site reads. “The frequency of bites has increased in recent years as a result of ecotourism feeding operations.”
Whitetip reef
The smallest shark of the five, the whitetip reef shark (Triaenodon obesus) is not the same fish as the open-ocean white-tips, which are much larger and capable predators.
Unlike many shark species, whitetip reef sharks can breathe without swimming and forcing water and oxygen through their gills.
Known for their placid behavior toward humans, whitetip reef sharks can be hand-fed, although there are obvious risks to doing so.
Caribbean reef shark
As its name suggest, the Caribbean reef sharks (Carcharhinus perezi) is found largely in the Caribbean Sea and is prohibited from harvest in United States waters.
Large for a reef shark (growing up to 10 feet in length), Caribbean reef sharks are another species that is popular in the international scuba community.
“The shark uses six keen senses to locate its prey: olfactory, visual, tactile (including water vibration sensitivity through a lateralis canal system), auditory, gustatory, and electric reception,” says a UF website. “The Caribbean reef shark is especially adapted to detecting low frequency sounds (indicative of a struggling fish nearby).”
Feeding the fish off the coast of Florida is illegal, but many dive operations in the Caribbean specialize in Caribbean reef shark feeding dives.
Shark attacks on humans are rare, according to UF, but these sharks are large and capable predators.
And you probably shouldn’t eat them, either.
“Another danger posed to humans by the Caribbean reef shark involves the accumulation of toxins in the flesh of the shark,” according to UF. “Since sharks are apex marine predators, they may contain toxic levels of mercury and other heavy metals due to bioaccumulation.”
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