Bull Shark, Carcharhinus leucas
Bull Shark, Carcharhinus leucas. Photography courtesy of the FAO.
Bull Shark, Carcharhinus leucas, Juvenile. Fish caught from coastal waters off Islamorada, Florida, February 2020. Length: 1.27 m (4 feet 2 inches). Catch, photograph and identification courtesy of Marc Eberlein, Grand Rapids, Michigan.
Bull Shark, Carcharhinus leucas, Juvenile. Fish caught from coastal river of Sebastian, Florida. Length: 1.27 m (4 feet 2 inches). Catch, photograph and identification courtesy of Ben Cantrell, Sebastian, Florida.
The Bull Shark, Carcharhinus leucas, is one of the largest members of the Requiem Shark or Carcharhinidae Family, that is known in Mexico as tiburón toro. They are named for their stout appearance, broad flat snout, and aggressive behavior. Globally, there are thirty-five species in the genus Carcharhinus, of which seventeen are found in Mexican waters, seven in the Atlantic, four in the Pacific, and six in both the Atlantic and Pacific Oceans.
The Bull Shark has a very stout body. They are pale to dark gray dorsally that transition to cream color ventrally. Their young have fins with dark tips. Their caudal fin is strongly asymmetrical with a well-developed lower lobe and a notch under the tip of the top lobe; their first dorsal fin is large, triangular with a pointed apex and originates over or slightly behind the pectoral fin insertions; their second dorsal fin is significantly smaller and originates slightly in front of the anal fin; and, their pectoral fins are large, broad and angular. Their head has short snout that is bluntly rounded and shorter than the width of the mouth and bluntly rounded, small eyes. Their mouth is equipped with broad, triangular and heavily serrated teeth on the upper jaw; the lower teeth have a broad base and are narrow and triangular with fine serrations. They do not have the interdorsal ridge found in similar sharks.
The Bull Shark is a coastal species that if found in lagoons, river mouths, and other low salinity estuaries normally at depths that are less than 30 m (100 feet) but on occasion at depths up to 150 m (490 feet). The Bull Shark is the best known of 43 elasmobranchs that are the only shark found in fresh water. They have been found over 4,000 km (2,500 miles) up the Amazon River and over 1,800 km (1,800 miles) up the Mississippi River. They are diadromous capable of swimming between fresh and salt water that makes them scientifically interesting. They are capable of traveling great distances in a short period of time, 180 km (112 miles) in 24 hours. They are capable of surviving in a wide rate of salinities including levels of 53 parts per thousand. They are also known to make seasonal migrations moving to cooler waters in the summer and returning to tropical climates in the winter. They reach a maximum of 4.0 m (13 feet 1 inch) in length and 316.5 kg (698 pounds) in weight with females being slightly larger than males. As of January 1, 2023, the International Game Fish Association world record stood at 316.5 kg (698 lbs) with the fish caught in coastal waters off Kenya in March 2001. They are normally solitary opportunistic hunters that consume bony fishes including smaller bull sharks and stingray as-well-as birds, crustaceans, dolphins, echinoderms, terrestrial animals and turtles. In turn their juveniles are preyed upon by various larger sharks, including adult Bull Sharks, the Sandbar Shark, Carcharhinus plumbeus, and the Tiger Shark, Galeocerdo curvier. Females reach sexual maturity at 18 years and males at 15 years. Reproduction occurs in river mouths and estuaries and is viviparous, with internal fertilization and yolk sac placenta, and gestation periods of 10 to 11 months and liter sizes of 1 to 13 miniature adults that are between 56 cm (22 inches) to 81 cm (2 feet 8 inches) in length. Mating occurs at sea and then the females migrate to fresh water areas which are free from other sharks. Their young are born live and capable of fending for themselves and remain in brackish waters for several months to avoid predation. They have lifespans of thirty-two years with females living longer than males.
The Bull Shark is a resident of all Mexican waters of the Atlantic and Pacific Oceans.
For sharks from the Atlantic Ocean the Bull Shark has a longer lower caudal fin lobe than other large sharks. However, for sharks found in the Atlantic Ocean they can be confused with the the Copper Shark, Carcharhinus brachyurus (slender body, long straight pectoral fins), the Dusky Shark, Carcharhinus obscurus (large eyes; slender body), the Finetooth Shark, Carcharhinus isodon (small narrow pectoral fins), and the Sandbar Shark, Carcharhinus plumbeus (interdorsal ridge). For sharks found in the Pacific Ocean they can be confused with the Bignose Shark, Carcharhinus altimus (long snout; interdorsal ridge), the Dusky Shark, Carcharhinus obscurus (large eyes, interdorsal ridge; large pectoral fins with concave rear margins, and the Sandbar Shark, Carcharhinus plumbeus (interdorsal ridge).
From a conservation perspective the Bull Shark is currently classified as Near Threatened. The Bull Shark is not targeted by commercial fishermen. They are caught has a by-catch of longliners and artisanal fishermen. Their meat is used for human consumption and for fish meal. Their fins are sold in Asian markets for use in fish fin soup and their skin is utilized in leather products. In some regions they are pursued by recreational anglers from shore, piers and bridges. They can also be found in large public aquariums. The Bull Shark is the “star” of the infamous movie “JAWS!” There have been multiple attacks of Bull Sharks on Humans documented over the years of which 27 have been fatal and due to their close proximity to humans is considered to be one of the most dangerous sharks in the world. Their long-term viability is currently threatened by overfishing, low reproductive rates and inshore habitat destruction caused by human developments. Due to misidentifications and underreporting from remote regions of the world the actual attacks are considered to be significantly understated.