Girard first documented the leopard shark as Triakis semifasciatum in 1855. Since then, the species name has been modified to semifasciata. The genus Triakis is derived from the Greek word "triakis" translated as three pointed, referring to this shark's three pointed teeth, while the species name semifasciata means half-banded, describing the distinctive markings found on this shark.
Triakis semifasciata is known as the leopard shark in the US and the UK, and is sometimes referred to as a cat shark. It is also known as leopardhai in Germany, leopardihai in Finland, luipaardhaai in the Netherlands, tiburón leopardo in Mexico, tollo leopardo in Spain, turbarão-leopardo in Portugal, and virli léopard in France.
Despite the fact that the two sharks do not share the same geographic distribution, the zebra shark (Stegostoma fasciatum) is sometimes confused with the leopard shark (Triakis semifasciata) as both animals are referred to by the common name leopard shark in Australia and South East Asia.
Leopard sharks have a relatively narrow range, found in the Eastern Pacific Ocean from Oregon to the Gulf of California in Mexico. Large populations occur in San Francisco Bay, and other large estuaries.
World distribution map for the leopard shark
The leopard shark is most commonly found in sandy or muddy bays and estuaries either at or near the bottom. The shark is most commonly encountered in 20 feet (6.1 meters) of water or less, but has been sighted up to 300 feet (91.4 meters) deep. Leopard sharks seem to prefer cool and warm temperate waters.
Importance to Humans
Leopard shark illustration
source Field Guide to Eastern Pacific and Hawaiian Sharks, U.S. Fish and Wildlife Service 1967
- · Distinctive Features
The leopard shark has a relatively broad and short snout. The prominent rounded dorsal fin of this shark originates over the inner margins of its pectoral fins. The second dorsal fin is pointed and averages about three-quarters the size of the first dorsal fin. The anal fin is diminutive in comparison to the leopard shark's second dorsal fin. The pectoral fins of the leopard shark are rather broad and roughly triangular in shape. The upper lobe of the tail is notched and elongated.
The leopard shark could possibly be mistaken for the swell shark (Cephaloscyllium ventriosum), which is reddish-brown and has a flattened head.
Recent research indicates that the erythrocytes (red blood cells) of the leopard shark are more diminutive and numerous than those of its relatives, the brown smooth-hound (Mustelus henlei) and the gray smoothhound (Mustelus californicus). This could theoretically provide the leopard shark with an edge over its chief competitors in estuarine environments by allowing the leopard shark to more easily absorb oxygen from the water.
The leopard shark is a strong swimmer and it often forms large nomadic schools that sometimes include brown smooth-hounds (Mustelus henlei), gray smooth-hounds (Mustelus californicus), and spiny dogfish (Squalus acanthias).
- · Coloration
The leopard shark is conspicuously covered with dark saddles and splotches. The dorsal surface of the animal varies in coloration from silver to a bronzed gray. The ventral surface of the animal is lighter and sometimes white.
- · Dentition
Leopard sharks produce tooth sets that form overlapping ridges between different tooth rows. The resulting effect is a large flattened and ridged surface on the upper and lower jaws. This type of dentition is often referred to as "pavement-toothed." The pointed surfaces of the toothed ridges of the leopard shark are capable of puncturing human skin. However, there are no reports of humans being bitten by this shark.
- ·Size, Age, and Growth
Leopard sharks can reach lengths of up to 7 feet (2.13 meters), but it is rare to find an individual larger than 6 feet (1.83 meters). The average size of an adult leopard shark is between 50 and 60 inches (120cm to 150 cm). Pups are born at a size of 8 to 9 inches (0.20 to 0.23 meters). The sharks reach maturity at a size of 3 to 3.5 feet (0.91 to 1.07 meters).
Leopard sharks feed on many species of fish including bat rays
courtesy Tony Chess/National Marine Fisheries Service
- · Food Habits
Leopard sharks feed primarily on benthic invertebrates and small fish. Their diet includes invertebrates such as crabs, shrimp, octopi, fat innkeeper worms (Urechis caupo), clam siphons, and fish such as midshipmen, sanddabs, shiner perch, bat rays, smoothhounds, and a variety of fish eggs. Leopard sharks have been known to mutilate their prey, taking only parts of the animals they ingest, leaving the rest. For example, a number of clam siphons have been found in multiple specimens of leopard shark. However, a body of a consumed clam has not been reported to be found.
- · Reproduction
Female leopard sharks are ovoviviparous and can produce litters of 4 to 33 pups. The gestation period of the shark is between ten and twelve months, and birth usually occurs between April and May.
Large fish, including the white shark, feed on leopard sharks
- Marine mammals prey upon young leopard sharks, and both juvenile and adults are vulnerable to large fish, including the white shark (Carcharodon carcharias).
Commercial and sport fishermen harvest the leopard shark. The shark is used primarily as a food source, and is sold both fresh and frozen.
Danger to Humans
The leopard shark poses virtually no danger to humans. The International Shark Attack File has a single report of an incident involving a human and a leopard shark. This incident did not reportedly cause any significant damage to the victim, and no bite was involved. However, leopard sharks do contain high levels of mercury and should not be consumed regularly, as per the warnings of the California Department of Fish & Game.
Leopard shark with yellow tag through dorsal fin
courtesy National Marine Fisheries Service
Due to the relatively late age of first reproduction, the slow growth rate, and the low reproduction rate, the leopard shark is potentially threatened by over-fishing. However, the shark is not currently listed as an endangered or threatened species. Management of this species in recent years is thought to have protected the core population of this species in waters off California and Oregon (US). The status of stocks off Mexico is currently unknown.
The leopard shark is considered to be at "Lower Risk" by the World Conservation Union (IUCN). The IUCN is a global union of states, governmental agencies, and non-governmental organizations in a partnership that assesses the conservation status of species.