Horn Shark, California Horn Shark, Pacific Horn Shark, Bullhead Shark.
Stout body. Large square head with prominent ridges above eyes. Two large dorsal fin, each with a spine at its origin. First dorsal fin origin anterior to pectoral fin insertion. Second dorsal fin origin level with pelvic fin free rear tip. Pectoral fins much larger than first dorsal. Pelvic fins about the same size as dorsal fins. High, short anal fin. Well developed caudal fin with square terminal lobe.
Dorsal coloration may be light brown, dark brown, or patches of both, with scattered small black spots. Spots may be absent on larger animals. Juveniles usually have more prominent light and dark areas and more spots.
Maximum length 120cm. Size at birth 15-16cm.
Temperate seas. Present on rocky reefs and in kelp forests. From intertidal to at least 152m but often found in shallow bays in water less than 10m deep.
The horn shark is found in the northeastern Pacific from San Francisco (in the summer) southward to the central Mexico including the Sea of Cortez.
Compagno suggested that the horn shark may also be present in South America but there is no evidence to support this. Any records of Heterodontus francisci from the southeastern Pacific are probably misidentifications of the closely related Galapagos bullhead shark.
In California, horn sharks are of no commercial value, but they are taken as bycatch in traps and trawls and occasionally by recreational anglers. In Mexico they are caught as a bycatch of the shrimp fishery and other bottom-trawling operations. In the northern Gulf of Mexico and likely on the Pacific side of Baja California they are caught as bycatch in the demersal gillnet fishery during the winter and spring. This species should be closely monitored in Mexico if the gillnet fishery expands, as bycatch levels could impact the Mexican population (Wade Smith, pers comm). These sharks are kept in many public aquaria in the United States as they are hardy, attractive, readily maintained, and will breed in captivity (Compagno 2001, Ebert 2003).
Citations and References
Carlisle, A.B. 2015. Heterodontus francisci. The IUCN Red List of Threatened Species 2015: e.T39333A80671300. https://dx.doi.org/10.2305/IUCN.UK.2015-4.RLTS.T39333A80671300.en. Downloaded on 26 November 2020.
Oviparous. Like other heterodontids, the horn shark lays auger shaped egg cases that measure roughly 12cm in length with a max. diameter of 6.4cm at the widest end. Although egg cases sometimes found laying on the sand, they are usually found securely screwed into tight crevices between rocks. Although their installation has not been witnessed, Port Jackson Sharks in Australia have been documented holding their egg cases in their mouths and rotating their bodies to literally screw the eggs into cracks. It is likely that the Californian horn shark uses a similar technique.
The horn shark’s diet consists of hard shelled crustaceans and molluscs that it crushes between plate-like molars. Juveniles often consume polychaete worms.
Horn sharks are sluggish swimmers that rest during the day in deep crevices or under overhangs. Suspected of migrating seasonally into deep water.
Reaction to divers
Easy to approach, remaining completely motionless unless molested, at which point horn sharks usually retreat deeper into crevices or caves where possible.
Quite easy to locate on shallow reefs in Southern California where it is most abundant.
La Jolla Cove is a well known shore dive north of San Diego where horn sharks are frequently sighted. If the swell is not too problematic, try searching for juveniles under rocks in the sea grass zone very close to the entry point. Adults tend to be in slightly deeper water e.g. around kelp holdfasts or under larger overhangs in 10-15m.
The beach in front of the commercial laundry near Avalon on Catalina Island is another great spot to see juvenile horn sharks at night. Each time I have been there, about a dozen small horn sharks have been sitting here and there in plain sight on the sand in about 8m of water.