Leopard Shark, Triakis semifasciata
The Leopard Shark, Triakis semifasciata, whose common Spanish name is tiburón leopard, is a species in the Hound Shark or Triakidae Family, known collectively as cazones in Mexico. Globally, there are five species in the genus Triakis, and only the species described herein is found in Mexican waters of the Pacific.
The Leopard Sharks have robust, long, slim, and humped bodies. They are overall silvery to bronzed-gray dorsally and transition to white ventrally. They are covered with conspicuous dark saddles and splotches dorsally, giving rise to their common name. Their head has a short bluntly rounded snout. Their eyes are large horizontal ovals with ventral nictitating membranes. Their mouth is convex and equipped with 41 to 55 teeth set in rows on the upper jaw and 34 to 45 teeth on the lower jaw. Their teeth, which are periodically shed and replaced, form a large central point and small accessory points at the sides and are arranged into a flat “pavement”-like surface with overlapping ridges. They have five gill slits, the last two located over their pectoral fin base. Their anal fin originates under the middle of the second dorsal fin and is much smaller than the second dorsal fin; their caudal fin is asymmetric with the upper lobe being notched and elongated and the lower lobe having no point; their first dorsal fin is large and rounded and originates over the inner margin of the pectoral fins; their second dorsal fin is pointed and about three-fourths the size of the first dorsal fin; and their pectoral fins are broad and triangle-shaped. All their fins have blunt tips.
The Leopard Sharks are a coastal schooling species found demersal in sandy and muddy bays and estuaries, normally at depths of less than 25 feet and occasionally at depths of 300 feet. Females are larger than males and reach a maximum length of 2.1 meters (6 feet 9 inches) whereas males reach a maximum length of 1.5 meters (4 feet 9 inches). They can weigh up to 18.4 kg (41 pounds). They are generally slow growing and take a long time to reach sexual maturity. They are known to undergo limited migrations based on water temperatures, salinity, and dissolved oxygen content. They reside in bays and estuaries during the spring and summer and move to warmer coastal waters during the winter. Most tend to remain within a particular area rather than undertake long movements elsewhere. They are nighttime predators feeding primarily on benthic invertebrates (crabs, shrimp, octopus, and clams) and a wide variety of small fish. They feed on tidal cycles coming into shallow waters on the incoming tides and retreating when the tide retreats. Juveniles are preyed upon by various marine mammals and large fish such as the Broadnose Sevengill Shark, Notorynchus cepedianus and the White Shark, Carcharodon carcharias. They have lower than normal red blood cells allowing them to adsorb higher oxygen levels and giving them an edge over their competitive predators. They are strong swimmers and known to form large schools that can include the Brown Smoothhound, Mustelus henlei, the Gray Smoothhound, Mustelus californicus, and the Pacific Spiny Dogfish, Squalus acanthias. Reproduction occurs on an annual basis via aplacental viviparity with young being nourished by the yolk and hatching inside the uterus. Gestation lasts from 10 to 12 months and litter sizes range from 4 to 33 pups measuring 20 cm (8 inches) to 23 cm (9 inches) in length. Females can mate with multiple males and as many as 36% of litters having multiple paternities. Females aggregate and normally deliver their young in very shallow water in coastal bays and estuaries. They have a lifespan of up to thirty years.
In Mexican waters the Leopard Sharks are found along the entire West Coast of Baja, within the southern two-thirds of the Sea of Cortez, and south along the coast of the mainland to Mazatlán.
The Leopard Shark is most likely confused with the Swell Shark, Cephaloscyllium ventriosum (reddish brown with flattened head).
The vast majority of Leopard Sharks are caught in California waters by recreational fishermen from piers, jetties, beaches, banks, and skiffs, by bow fishermen in shallow waters, and by spearfishermen; catch levels are on the order of 50 to 550 metric tons per year. Commercially, they are taken incidentally in gill nets, longlines, and trawl fisheries with catch levels being minor and on the order of 10 metric tons per annum. This species has also been harvested for the cold-water aquarium trade and is highly prized for its distinctive markings and hardiness being capable of living for up to 20 years in captivity. Poaching of pups for the aquarium trade has been a significant problem with up to 50,000 pups being taken per annum which far exceeds the recreational and commercial catches of this species. They have thus become heavily regulated by the State of California with the establishment of length restrictions and daily bag limits. They are considered harmless to humans. Their meat is considered excellent and is sold fresh or frozen. They are known, however, to be contaminated with mercury, pesticides, and PCBs, and I for one, would not consume this fish. From a conservation perspective they are currently considered of Least Concern, noting that they are targets of heavy fishing pressure regionally, have slow growth rates with long reproductive cycles, and are experiencing ongoing loss and alteration of the inshore habitats needed for their foraging and nurseries.
Leopard Shark, Triakis semifasciata. Fish caught from coastal waters off Santa Catalina Island, California, September 2016. Length: 91 cm (36 inches). Catch courtesy of Marty Dufek, Long Beach, California. Photo and identification courtesy of Chris Wheaton, Loreto, Baja California Sur.