Horn Shark, Heterodontus francisci
The Horn Shark, Heterodontus francisci, whose common Spanish name is tiburón puerco, is a species in the Bullhead Shark or Heterodontidae Family, known collectively as tiburones cornudos in Mexico. They are named for their dorsal fin spines. Globally, there are only eight species in the genus Heterodontus, two of which are found in Mexican waters, both in the Pacific.
The Horn Sharks have rectangular blocky bodies that are easy to identify. They vary in color from dark brown to light gray on their back and sides and transition to white ventrally. They are covered with small dark spots that are about one-third the diameter of their eyes and have a dusky patch below their eyes. Their coloration allows them to easily blend with their surroundings. Their head is conical and elevated with a pig-like snout and a small mouth that opens anteriorly. They have a low bony ridge above each eye that ends abruptly at the rear; the space between their eyes is deeply concave. Their teeth morphology varies being sharp at the front for grasping prey and flat at the back for crushing shellfish. They have five gill slits, the first of which is enlarged and the second and third of which are over their pectoral fins. Their caudal fin is asymmetric. They have two virtually identical dorsal fins, each with a spine at the front (a key to identification). Their first dorsal fin originates over the pectoral fin base. They have small denticles on their flank but their skin is smooth to the touch.
The Horn Sharks are a slow and sluggish benthic species found from the intertidal zone to relatively deep waters in both rocky and sandy habitats. They move to deeper waters during the summer. They reach a maximum length of 1.2 meters (4 feet 0 inches). They are elusive fish that spend their days hiding under ledges, in caves, and in kelp beds and emerge at night to feed on seafloor benthic invertebrates including abalone, crabs, oysters, polychaete worms, shrimp, and occasionally small fish. They are poor swimmers and use their strong pectoral fins to crawl along rocks. They have a high degree of segregation with juveniles being found in deeper waters at depths of 655 feet over sandy bottoms and adults being found in shallow waters at depths of less than 35 feet within rock structures. They are site-specific with a small home range and return to the same location during the day; they can be found in the same location for many years. Reproduction is oviparous with females laying spiral egg cases that they wedge into crevices; pups require six to nine months to hatch and emerge as 14 cm (5.5 inch) miniature adults. They prefer water temperatures in excess of 21oC (70oF).
In Mexican waters the Horn Shark have a limited range in being found in the Pacific along both coasts of Baja and along the northwest coast of the mainland; the are absent from Guaymas southward along the central and southwest coasts of the mainland.
The Horn Shark can be confused with the Mexican Horn Shark, Heterodontus mexicanus (body spots greater than one-half the eye diameter).
The Horn Sharks are targeted by spearfishermen in certain locations with their spines being retained to make jewelry. They are also an accidental by-catch in crab traps, gillnets, and trawling nets. They have no commercial value and their conservation status is not of concern. They are consider harmless and will only attack humans if provoked.
Horn Shark, Heterodontus francisci. Fish caught in coastal waters off Loreto, Baja California Sur, April 2016. Length 55 cm (22 inches). Catch, photo and identification courtesy of Chris Wheaton, Fullerton, CA.
Horn Shark, Heterodontus francisci. Underwater photo taken in coastal waters off La Jolla, CA, September 2013. Length: 76 cm (30 inches). Photo courtesy of Bob Hillis, Ivins, UT.