Beautiful shark known to have many unique behavioral characteristics
The Leopard shark (Triakis semifasciata) is a species of shark in the family Triakidae. It is found along the northeast Pacific from Oregon to the Gulf of California in Mexico. It has an unmistakable pattern of black saddle-like markings and large spots over its back. This shark is a known schooling shark, and large schools of Leopard sharks are a common sight in bays and estuaries, swimming over sandy or muddy flats or rock-strewn areas near kelp beds and reefs. These sharks are quite common in shallow water.
Family: Triakidae – Houndsharks
Common Name– Ground Sharks
Common Name– Houndsharks
Average Size and Length: They are born around 20 cm/7.8 inches. Mature males have been measured between 70-119 cm/2.3-3.9 feet. Mature females have been measured between 110-129 cm/3.6-4.2 feet. The maximum recorded for a male is 150 cm/4.9 feet, and the maximum for a female is 180 cm/5.9 feet. Some mention a female at 6.9 feet, but this may be false.
Average Weight: The heaviest known Leopard shark weighed 41 pounds.
Current Rare Mythical Sightings: The first scientific name applied to the Leopard shark was Triakis californica, by British zoologist John Edward Gray in the 1851 list of the specimens of fish in the collection of the British Museum. However, Gray did not provide the name with a proper description, rendering it a nomen nudum. In December 1854, American ichthyologist William Orville Ayres gave a lecture describing the species as Mustelus felis, which included the first scientific description of the species. His lecture was reprinted first in The Pacific, a San Francisco newspaper, and then in the journal Proceedings of the California Academy of Natural Sciences. In April 1855, French biologist Charles Frédéric Girard published another description of this species, naming it Triakis semifasciata. 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) (Pietsch, T.W.; Orr, J.W.; Eschmeyer, W.N. (2012). “Mustelus felis Ayres, 1854, a Senior Synonym of the Leopard Shark, Triakis semifasciata Girard, 1855 (Carchariniformes: Triakidae), Invalidated by “Reversal of Precedence”).
The epithet semifasciata comes from the Latin words, semi (“half”) and fasciatus (“banded”), describing this shark’s dorsal pattern of saddle-like markings. The genus Triakis contains two subgenera, Triakis and Cazon. The Leopard shark is placed within the subgenus Triakis along with the Banded houndshark. A 2006 phylogenetic analysis by J. Andrés López and colleagues, based on protein-coding genes, 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 (López, J.A.; J.A. Ryburn; O. Fedrigo; G.J.P. Naylor (2006). “Phylogeny of sharks of the family Triakidae (Carcharhiniformes) and its implications for the evolution of carcharhiniform placental viviparity“. Molecular Phylogenetics and Evolution. 40 (1): 50–60).
Teeth and Jaw: The mouth is strongly curved. There are furrows at the corners of the mouth extending onto both jaws, with those on the lower jaw almost long enough to meet at the midline. The tooth rows number 41–55 in the upper jaw and 34–45 in the lower jaw; each tooth has a slightly oblique, smooth-edged cusp in the center and 1–2 small cusplets on either side. Teeth are arranged into a flat, pavement like surface with overlapping ridges. Replacement teeth take 9-12 days on average to repopulate.
Head: The snout is short and rounded. They have well-developed, triangular flaps of skin in front of the nares. The eyes are large and oval, with a nictitating membrane.
Their eyes contain very few cone cells, likely due to the murky water they inhabit (Sillman, A.J.; G.A. Letsinger; S. Patel; E.R. Loew & A.P. Klimley (1998). “Visual pigments and photoreceptors in two species of shark, Triakis semifasciata and Mustelus henlei“. Journal of Experimental Zoology Part A: Comparative Experimental Biology. 276 (1): 1–10).
Tail: 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.
Demographic, Distribution, Habitat, Environment and Range: The Leopard shark can be found in the northeast Pacific from Coos Bay, Oregon to the Gulf of California in Mazatlán, Mexico (45°N – 19°N, 126°W – 105°W). They inhabit cool to warm temperate waters inshore and offshore on the continental shelf. They are most often found on or near the bottom intertidal to 13 feet. They have also been recorded as deep as 298 feet. They prefer shallow, enclosed, muddy bays and mud flats, flat sandy areas, rocky areas or near rocky reefs, and beds of kelp.
These sharks are somewhat migratory, but within a very limited range; they do not travel far and mostly remain local. A few Leopard sharks, particularly in the north, leave their coastal habitats in winter and return in early spring. A study in Tomales Bay in northern California determined that they depart when the water temperature drops below 50–54 °F; one tagged shark was found to have swum some 87 mi south (Hopkins, T.E.; J.J. Cech (Jr.) (2003). “The influence of environmental variables on the distribution and abundance of three elasmobranchs in Tomales Bay, California“. Environmental Biology of Fishes. 66 (3): 279–291).
In northern areas, females use bays and sloughs as nursery areas, while to the south they give birth in more open areas. Known breeding grounds along the coast of California include Humboldt Bay (pups are birthed in eelgrass), Tomales Bay, Bodega Bay, San Francisco Bay, Elkhorn Slough, Morro Bay, Santa Monica Bay (Los Angeles), Catalina Harbor (Santa Catalina Island. These pups are birthed in 3.3 feet of water with the female’s dorsal fins exposed out of the water. Pups will remain in about a foot of water for a period of time.), and San Diego Bay.
Diet: Leopard sharks are opportunistic predators. They feed on burrowing invertebrates and other bottom animals. Their diets vary with the size of the shark and the season, as well as location. Sub populations and groups seem to prey on different prey items then some others.
The Great White shark and the Broadnose Sevengill shark are known to prey on smaller Leopard sharks. There may even be a case of a Broadnose Sevengill shark attempting to ambush a Leopard shark on a tidal mudflat in Humboldt Bay, but further records need to be assessed.
Ram-Suction Index: The Leopard shark captures prey by expanding its buccal cavity to create a suction force, which is aided by its labial cartilages swinging forward to form the mouth into a tube. Simultaneously, the shark protrudes its jaws forward to grip the prey between its teeth (Ferry-Graham, L.A. (1998). “Effects of prey size and mobility on prey-capture kinematics in leopard sharks Triakis semifasciata” (PDF). Journal of Experimental Biology. 201 (16): 2433–2444). They possibly such clams out of their shels, and worms from burrows.
Aesthetic Identification: The Leopard shark is a stout but slender shark and has a unique and unmistakable pattern of dark black saddles and spots on a tan to greyish background. These fade right into the whiteish ventral side of the shark. In adult sharks, the saddle marks become light-centered. The first dorsal fin is large and positioned about halfway between the pectoral and pelvic fins. The second dorsal fin is almost as large as the first and much larger than the anal fin. The pectoral fins are wide and triangular.
Biology and Reproduction: They are ovoviviparous without a yolk sac placenta, having 4-29 pups per litter, and possibly as many as 32. The number of pups does increase with the size of the female. Multiple males may father a litter from a single mother. Birthing happens between March and June after a 10-12-month gestation period. Mating will occur in early summer. The only known mating observation in the wild was in 2004 off La Jolla, amongst nine sharks gathered 62 feet from shore in water 0.98–9.84 feet deep. (Smith, S.E. (2004). “Leopard Shark (Triakis semifasciata) Mating Activity Observed off La Jolla, California“.). Their growth rate is somewhat slow, especially after the first 3-4 years of life. Male Leopard sharks grow an average of 2.0 cm per year, reaching maturity at an age of 7–13 years and a length of 2.3–3.9 feet, while females grow an average of 2.3 cm per year, reaching maturity at an age of 10–15 years and a length of 3.6–4.3 feet. Larger sharks are known to be slower to grow. The maximum lifespan is an estimated 30 years.
Though 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 gene pools have been identified along the Californian coast between Humboldt Bay and San Diego. 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 dispersed. Off Baja California, the Leopard sharks on the Pacific side are probably distinct from those in the northern Gulf of California. It is also possible that they may return to their birthplace to breed, but evidence and more data is needed. (Lewallen, E.A.; T.W. Anderson; A.J. Bohonak (2007). “Genetic structure of leopard shark (Triakis semifasciata) populations in California waters“. Marine Biology. 152 (3): 599–609).
Compared to the related Grey smoothhound and Brown smoothhound 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).
Known parasites include the tapeworms Phyllobothrium riseri, Lacistorhynchus dollfusi and Paraorygmatobothrium barber, as well as the copepods Echthrogaleus eoleoptratus and Achtheinus oblongatus.
Behavioral Traits, Sensing and Intelligence: Leopard sharks are active and strong swimming. These sharks are known to form a school that is large and nomadic. They have also been observed forming schools with the Grey smoothhound, Brown smoothhound, and the Piked dogfish. Some have observed large schools in warm waters just from the discharge of power plants. Their range is small, traveling only up to 93 miles. Since their travel is limited, sub populations have begun to evolve. They have also been observed resting on sand or rocks. This shark is also known to be nocturnal. Some choose to rest by day and actively swim several miles in search of food at night.
During summer days, large aggregations of mature females assemble in shallow bays and estuaries, scattering at night. Females follow the warmest patches of water, allowing them to raise their internal body temperatures by up to 5.4 °F, they are speculated to be taking advantage of the heat to speed their growth and that of their gestating young (Hight, B.V.; C.G. Lowe (2007). “Elevated body temperatures of adult female leopard sharks, Triakis semifasciata, while aggregating in shallow nearshore embayments: Evidence for behavioral thermoregulation?“. Journal of Experimental Marine Biology and Ecology. 352: 114–128).
captivity, larger sharks have been observed establishing their dominance over smaller individuals via light nips to the pectoral fins.
They are skittish and quick to exit when in presence of humans.
Speed: The Leopard shark is a strong swimming shark. It swims with a strong undulating motion. Groups are known to follow tides into intertidal mudflats in search of food.
Leopard Shark Future and Conservation: They are currently of least concern. This could change if conservation efforts change. They are common among their range. Their meat is valuable though. They have been intensively fished commercially in the past, with a population decline in the 1980’s. From the 1990’s through today, populations in the USA are managed. Development does pose a threat to these sharks. They are a hardy species and adapt well in captivity when they are young, and for that reason are very popular in public aquariums. They are recorded to live more than 20 years in captivity.
Leopard Shark Recorded Attacks on Humans: Not a threat to humans. There has been one account af an interaction with a freediver, but no injuries other than minor cuts/bruising.