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The leopard shark ( Triakis semifasciata) is a species of houndshark, in the family Houndshark. It is found along the Pacific coast of North America, from the U.S. state of Oregon to Mazatlán in Mexico. Typically measuring long, this slender-bodied shark is immediately identifiable by the striking pattern of black saddle-like markings and large spots over its back, from which it derives its common name. Large schools of leopard sharks are a common sight in and estuary, swimming over sandy or muddy flats or rock-strewn areas near and . They are most common near the coast, in water less than deep.
Active-swimming , groups of leopard sharks often follow the tide onto intertidal zone mudflats to forage for food, mainly , Echiura, , shrimp, bony fish, and roe. Most leopard sharks tend to remain within a particular area rather than undertaking long movements elsewhere, which has led to genetic divergence between populations of sharks living in different regions. This species is aplacental viviparous, meaning that the young hatch inside the uterus and are nourished by yolk. From March to June, the female gives birth to as many as 37 young after a gestation period of 10–12 months. It is relatively slow-growing and takes many years to mature.
Harmless to humans, the leopard shark is caught by commercial and recreational fisheries for food and the aquarium trade. This species is mostly fished in the waters off California where, after a period of population decline in the 1980s, new fishing regulations in the early 1990s reduced harvesting to sustainable levels. The International Union for Conservation of Nature has assessed this species as of Least Concern, while noting that local Fish stocks may easily become overfishing because of the shark's slow growth and limited migratory habits.
Despite M. felis being the senior synonym, an error in recording the dates of publication resulted in the widespread use of T. semifasciata as the leopard shark's scientific name. As a result of this long-standing error, Triakis semifasciata came to be recognized as the valid name (as a nomen protectum) and Mustelis felis was invalidated (as a nomen oblitum). The specific epithet semifasciata comes from the Latin words semi ("half") and fasciatus ("banded"), describing this shark's dorsal pattern of saddle-like markings. In older literature, this species may be referred to as "tiger shark" or "Scyliorhinidae".
The genus Triakis contains two subgenera, Triakis and Cazon. The leopard shark is placed within the subgenus Triakis along with the banded houndshark ( T. (Triakis) scyllium). (1984). 9789251013847, Food and Agricultural Organization. ISBN 9789251013847 A 2006 phylogenetic analysis by J. Andrés López and colleagues, based on protein-coding , revealed that Triakis and Cazon are in fact not closely related, and additionally that the leopard shark may be the most basal member of its family.
While a few leopard sharks have been documented traveling hundreds of kilometers, most individuals tend to remain in a localized area for much of their lives. This low level of dispersal has led to genetic divergence across its range. Seven discrete have been identified along the coast between Humboldt Bay and San Diego. Of these, the Humboldt Bay subpopulation is perhaps the most isolated, with the sharks there maturing at a larger size and producing fewer offspring than those from other areas. By contrast, the area around Los Angeles represents a genetic transitional zone between subpopulations whose boundaries are more diffuse. Off Baja California, the leopard sharks on the Pacific side are probably distinct from those in the northern Gulf of California. Although there is equivocal evidence for natal philopatry (returning to one's birthplace to breed) in this species, proximity to established breeding grounds likely contributes to the structuring of these different subpopulations.
The large first dorsal fin is positioned about halfway between the pectoral fin and ; the second is almost as large as the first and much larger than the anal fin. The pectoral fins are wide and triangular. The lower lobe of the caudal fin is well-developed in adults but less than half the length of the upper lobe, which has a strong ventral notch near the tip. The coloration is unique, consisting of prominent black "saddles" and large black spots running along the back, on a silvery to bronzy gray background. Adult sharks often have more spots and saddles with lighter centers compared to juveniles. The underside is whitish and plain. The average length of a leopard shark is . Rarely males may grow to and females , and there is a record of an exceptional female that measured long. The heaviest known leopard shark weighed .
From birth, leopard sharks form large schools, generally segregated by age and sex; these groups may intermingle with grey smoothhound or brown smoothhounds ( Mustelus californicus and M. henlei) and spiny dogfish ( Squalus acanthias). These schools are apparently nomadic, often appearing suddenly in an area for a few hours before vanishing just as quickly. In captivity, larger sharks have been observed establishing their dominance over smaller individuals via light nips to the pectoral fins. During summer days, large aggregations of mature females assemble in shallow bays and estuaries, dispersing at night. As these females follow the warmest patches of water (allowing them to raise their internal body temperatures by up to , they are speculated to be taking advantage of the heat to speed their own growth and that of their gestation young. The membership of these aggregations is inconstant, with individual females periodically switching between different sites scattered over several kilometers.
Compared to the related grey and brown smoothhounds that share its range, the leopard shark has smaller and more numerous red blood cells, allowing it to process oxygen more efficiently. This may be an adaptation for foraging in deoxygenated Estuary environments.Martin, R.A. Estuaries: Leopard Shark. ReefQuest Centre for Shark Research. Retrieved on August 9, 2009. Their eyes contain very few , likely due to the murky water they inhabit. Small leopard sharks fall prey to larger sharks such as the great white shark ( Carcharodon carcharias) and the broadnose sevengill shark ( Notorynchus cepedianus). On one occasion, a sevengill shark was seen ambushing a leopard shark on a tidal mudflat in Humboldt Bay, striking with such momentum that the larger predator momentarily beached itself.Martin, R.A. Sandy Plains: Broadnose Sevengill Shark. ReefQuest Centre for Shark Research. Retrieved on August 9, 2009. Known parasites of this species include the Phyllobothrium riseri, Lacistorhynchus dollfusi and Paraorygmatobothrium barber, as well as the Echthrogaleus eoleoptratus and Achtheinus oblongatus.
The leopard shark captures prey by expanding its buccal cavity to create a suction force, which is facilitated by its lip swinging forward to form the mouth into a tube. Simultaneously, the shark protrudes its jaws forward to grip the prey between its teeth. As with other sharks, the teeth of the leopard shark are periodically shed and replaced; it takes 9–12 days for a replacement tooth to move into position. Leopard sharks have been caught with stomachs filled with clam siphons, which the sharks seize before the clams can retract and break off with a levering motion of their bodies. On occasion, the shark tears the entire clam body out of its shell this way. Other sharks examined have had stomachs containing whole innkeeper worms with no bite marks, suggesting that the sharks sucked them out of their burrows. Under a hollow bridge support in San Francisco Bay, a group of leopard sharks and spiny dogfish have been observed feeding on a dense school of anchovies by slowly swimming counterclockwise through the clockwise-swimming school, and swallowing any anchovies that accidentally entered their open mouths.
In some places, this species feeds only on a few prey types and little else (e.g. innkeeper worms and cancrid crabs in Tomales Bay, jack silverside ( Atherinopsis californiensis) eggs and the crabs Romaleon antennarium and Metacarcinus magister in Humboldt Bay). The predominant prey taken depends on location, time of year, and age. For example, in the Elkhorn Slough at Monterey Bay, cancrid crabs and innkeeper worms are mostly eaten in winter and spring, fish eggs from winter to early summer, bony fish in summer, and grapsid crabs and clams in fall. Young sharks feed mostly on crabs and transition to clam siphons, fish eggs, and innkeeper worms once they reach long. The largest sharks are the ones that consume the most fish.
Females give birth to 1–37 young annually from March and July (most in April or May), with the number of pups increasing with female size. Multiple males may father a litter from a single mother In Humboldt and San Francisco Bays, females drop their pups in beds of eelgrass that provide both shelter and food. In Catalina Harbor, females give birth on flats in of water, their backs and dorsal fins exposed; the pups stay in even shallower water less than deep. Mating occurs in early summer following birth; the only known observation of this in the wild was in 2004 off La Jolla, amongst nine sharks gathered from shore in water deep.Smith, S.E. (2004). "Leopard Shark ( Triakis semifasciata) Mating Activity Observed off La Jolla, California". Southwest Fisheries Science Center, San Diego. Note.
Newborn leopard sharks measure around long. Relatively slow-growing after the first 3–4 years of life, male leopard sharks grow an average of per year, reaching maturity at an age of 7–13 years and a length of , while females grow an average of per year, reaching maturity at an age of 10–15 years and a length of . Individuals of the same age can vary significantly in size and large sharks are especially slow-growing: one specimen was documented to have gained only in length over 12 years. The maximum lifespan of this species is estimated to be 30 years.
Most of the fishing for leopard sharks occurs in the waters off California, where commercial landings peaked at in 1983 and has averaged annually since 1991. These figures are believed to be underestimates, as an unknown portion of the leopard shark catch is recorded simply as "shark". In recent decades the number of sharks taken recreationally has exceeded those taken commercially, with sport fishers catching an average of 52,000 sharks per year from 1980 to 1988, and 45,000 sharks per year since 1993. (2025). 9781879906570, ANR Publications. ISBN 9781879906570 This species contributes negligibly to fishery landings off Oregon. The status of leopard sharks off Mexico is uncertain, although Mexican shark fisheries tend to focus more on larger species.
The International Union for Conservation of Nature (IUCN) has assessed the leopard shark as of Least Concern. It is highly susceptible to local depletion due to its slow growth rate and low level of exchange between regional Fish stocks. It was considered for, but is not managed under, the U.S. Pacific Fishery Management Council's (PMC) 1982 Groundfish Management Plan. In 1992, the State of California imposed a recreational minimum size limit of and a possession limit of three fish, a move that was strongly supported and promoted by the sport fishing community. In 1993, the State also instituted a minimum size limit of for the commercial harvesting of all sharks and rays, including for the aquarium trade. In addition, Californian restrictions on the use of certain types of fishing gear in near-shore waters confer good protection to this shark's core population. These management measures seem to have successfully reduced fishing mortality and halted the population decline from the 1980s; the status of the leopard shark off California is regarded as secure, with demographic models estimating an annual population increase of 3–6% with sustainable fishing.
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