Background

Tanks:


To keep a shark, you must have at least a 50 gallon tank. Some sharks may require a larger tank, especially if the shark can grow more than a foot long. The aquarium will need a cover so that the shark can not jump out. The aquarium should be around 76-80 degrees Fahrenheit. Be sure to check the temperature weekly. The aquarium should have gravel at the bottom, but only about an inch. The gravel should be cleaned regularly, along with the rest of the tank.

Sphyrna tiburo:

Karl Linnaeus first described this species as Sphyrna tiburo in 1758 after initially naming it Squalus tiburo. Synonyms referring to this species in past scientific literature include S. vespertin. The genus name Sphyrna is derived from the Greek word "sphyra" which translates as hammer. Bonnetheads are

the smallest species in the family Sphyrnidae. There are approximately 10 related species of hammerheads throughout tropical and temperate regions including the scalloped hammerhead (Sphyrna lewini), great hammerhead (Sphyrna mokarran), and smooth hammerhead (Sphyrna zygaena). The bonnethead is limited to warm waters of the Northern Hemisphere, ranging in the Atlantic Ocean from New England (U.S.) (rare) south to the Gulf of Mexico and Brazil. It is common throughout the Caribbean Sea including Cuba and Bahamas. This shark is rare in Bermuda. In the Pacific, this shark can be found from southern California towaters off of Ecuador. Summertime finds the bonnethead commonly residing in the inshore waters off the Carolinas and Georgia (U.S.) while during the spring, summer, and autumn it is found off the coast of Florida and in the Gulf of Mexico. Bonnetheads move closer to the equator, as waters grow colder during the winter months. Bonnetheads reside on continental and insular shelves, over reefs, estuaries and shallow bays from depths of 32-262 feet (10-80 m). They usually occur in small schools of up to 15 individuals, however during migration events they are seen in groups of hundreds or thousands. As spawning time approaches, bonnetheads tend to group by gender. During pupping season; females predominate in shallow waters where they give birth. Bonnetheads travel long distances everyday, following changes in the water temperature. This preference for water temperatures over 70°F (21°C) leads to migrations to warmer waters during the winter months. As a result, the bonnethead is found closer to the equator during the winter, moving back to higher latitudes during the summer. This species must swim continuously so that its gills receive oxygen from the water, otherwise it will sink. Although this shark is not territorial, it appears a hierarchy exists within groups of bonnetheads. Another interesting aspect of this species is a cerebrospinal fluid used in chemical communication among individual bonnetheads, informing others when there is a bonnethead in the area. Further studies are needed to learn more about this communication system. The shovel- or bonnet-shaped head is a distinguishing characteristic of this species, making it easy to identify among hammerhead sharks. The eyes are located at the ends of the evenly rounded lobes of the flattened head, increasing the field of vision. When the bonnethead swims, the head rolls from side to side. The arched mouth is located ventrally. The body is moderately compact and lacks a mid-dorsal ridge. The high first dorsal fin originates just behind the base of the pectoral fins. The second dorsal fin is slightly less than ½ as long as the base of the first dorsal fin with a slender free rear corner. The pectoral fins are short and the anal fin has only a slight indentation. The caudal fin has a nearly straight upper margin with a lower lobe about 1/3 as long as the upper lobe with a nearly straight rear edge. Bonnetheads lack air bladders and have strong digestive chemicals in their specialized intestines. Bonnetheads can be distinguished from other species by the flattened, bonnet-shaped head that is rounded between the eyes rather than hammer-shaped. Also, the head lacks a notch at the midline. It is the smallest of the hammerhead-type (family Sphyrnidae) sharks, reaching an average of 3-4 feet in length in comparison to the scalloped hammerhead which grows to an average of 6 feet and the great hammerhead growing to almost 20 feet in length. Bonnetheads feed during daylight hours primarily on crustaceans, dominated by blue crabs. They also feed on mantis shrimp (Squilla empusa), pink shrimp (Penaeus durorarum), mollusks, and small fishes. Occasionally bonnetheads will also feed on seagrasses as documented by stomach contents of some individuals. This species has been reported burrowing under coral heads in search of small fishes and invertebrates in the waters of southern Florida. Females tend to feed more often due to the need for increased amount of energy budgeted for reproductive efforts. Prey items appear to be correlated with seasonality as well as habitat. Although crustaceans are the primarily food source throughout the year, during the autumn diversity of prey items increases with the inclusion of spider crabs (Libinia dubia), purse crabs (Persephona punctata), stone crabs (Menippe mercenaria), and various cephalopods including octopus. Bonnetheads residing inside bays feed on a less diverse array of prey items than those caught off beaches in open waters. The bonnethead has evolved well-developed sensory and nervous systems that allow them to be efficient predators. Vision and hearing capabilities are exceptional as well as the sensitivity of the lateral line to small vibrations, alerting them to nearby potential prey. Upon locating a prey item, the bonnethead swims slowly within range followed by a quick acceleration to attack that item. The item is then crushed with the molariform teeth. There are two jaw closing phases, continuing the closure of the jaws. This differs from the capture event typical of other sharks, where the jaws are initially closed and biting ceases at jaw closure. This allows the bonnethead to take advantage of prey that is not available to other species of sharks. After the prey is crushed, it is moved by suction to the esophagus. In Florida waters, bonnetheads are believed to mate during the spring and autumn or perhaps even year-round. In the waters off the coast of Brazil, mating occurs during the spring. After mating, the females can store sperm for up to four months prior to actually fertilizing the eggs. The control over the fertilization period is believed to be an adaptation to ensure that the pups are born during optimal conditions for their survival. Bonnetheads are "viviparous", or live bearing. Female bonnetheads produce eggs that are maintained and nourished by a yolk-sac during the initial phase of gestation. The eggs withing the female are tough but elastic with folded ends allowing for growth of the embryos. The embryos released from the eggs absorb the yolk-sac. This sac attaches to the uterine wall of the mother forming a yolk-sac placenta. Blood vessels running through this placenta provide nourishment until birth of the embryo. Also, after hatching, sections of the uterine wall come together to separate each embryo and its placenta in its own uterine compartment. The gestation period, shortest among all sharks, is only four to five months.