The sandbar shark is a migratory shark belonging to the family Carcharhinidae and found in many warm regions of the Atlantic and Pacific oceans. This shark spends much of its time seeking food at the bottom of shallow-water areas, and may migrate each year in response to changing water temperatures. Its primary distinguishing feature is its unusually tall dorsal fin. Typically, the female sandbar shark becomes impregnated every two years, following violent courtship behavior on behalf of the male.
Generally, the sandbar shark is found in warm, shallow, smooth-bottomed regions of the Atlantic and Pacific oceans, which can include areas as diverse as Cape Cod and the Galapagos Islands. It tends to avoid waters directly adjacent to the beach, however, and thus is usually not considered a significant threat to humans. This shark usually feeds on bottom-dwelling prey, such as rays, eels, octopi, crabs, and squid. It tends to hunt between dusk and dawn.
Many sandbar sharks perform at least one long-distance migration each year, a behavior which scientists believe is motivated by the need to seek warmer water temperatures. Evidence for this theory can be found in the fact that sandbar sharks living in waters that tend to remain warm all year — such as those surrounding Hawaii — usually do not migrate. In most cases, migrating male sandbar sharks travel in groups, while female specimens journey alone.
A sandbar shark can be recognized by its dorsal fin, which tends to be much taller than those of other sharks in the Carcharhinidae family. Its skin can range in color from bluish-gray to brown. A mature sandbar shark can reach a length of up to 7 feet (2.13 m), although fully grown specimens more commonly measure approximately 5 feet (1.52 m). Mature sharks usually weigh between 120 and 140 pounds (54.43 and 63.5 kg).
Male sandbar sharks tend to display fairly violent courtship behavior, following a female and biting her repeatedly until she permits intercourse. Females usually become pregnant once every two years — most often in late spring or early summer — and carry their litter for approximately one year. These sharks are viviparous, which means that their pups are fed by a placental sac prior to birth. Litters can range greatly in size, with some numbering as few as six pups and others as many as twelve. Pups are usually born in water that is quite shallow, which may prevent them from becoming the prey of larger sharks.