Featured Elasmobranch – Mexican Hornshark

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Featured Elasmobranch – Mexican Hornshark

October 2010

Photo credit: Helmut Debelius (1972)

Mexican Hornshark

Heterodontus mexicanus (Taylor & Castro-Aguirre, 1972)

Family Heterodontidae (Bullhead or Horn Sharks)

Identification: A small cylindrical shark that has a very short and bluntly rounded snout. It is light grey-brown to dark grey in color, with large black spots (equal to or greater than half of the eye diameter) on fins and body. Between the bony eye-ridges there is a pale colored bar, as well as one or two indistinct, dusky blotches underneath the eye. A very stout dorsal spine precedes each dorsal fin, with the first dorsal fin origin over the pectoral fin bases. The pectoral fins are quite large, and an anal fin is present. This shark family is the only group with a combination of dorsal fin spines and an anal fin.

Size: A relatively small shark with a maximum total length of 55 cm (1.8 ft) for males, and 70 cm (2.3 ft) for females. Size at birth is about 14 cm (0.5 ft) total length. Males reach maturity at about 40-50 cm (1.3-1.6 ft) total length. Age and length of female maturity remain unknown.

Distribution: This species is endemic to the East Pacific. It ranges from Mexico (southern Baja California, the Gulf of California, and the southern Pacific coast) down to Guatemala, Panama, Colombia, and most likely Ecuador and Peru. It is quite common in the upper Gulf of California.

Habitat: A warm-temperate and tropical shark found in littoral continental waters, 20-50 m (66-164 ft) in depth, on rocky habitats including coral reefs and seamount. It can also be found over sandy or soft bottom areas.

Biology: Oviparous reproductive mode, with egg cases possessing long tendrils and thick, rigid T-shaped spiral flanges. The egg cases are 8-9 cm in length, with young hatching around 14 cm in length. The longevity, age at maturity, gestation time, and litter size are unknown. These sharks feed on crabs and demersal fishes including midshipman.

General interest: The conservation status of this species has been assessed as “Data Deficient”. Minimal interest to fisheries, but is taken as by-catch in bottom gillnets and shrimp trawling operations, and sometimes utilized as fishmeal. Occasionally, the meat is used for human consumption. This is a hardy species, and if released soon enough, can survive capture in drift and trawl nets. In the Gulf of California, this species co-exists with a similar species, Heterodontus francisci, and the two are frequently confused in the field.

By James D.S. Knuckey
Pacific Shark Research Center
Moss Landing Marine Laboratories
8272 Moss Landing Road
Moss Landing, CA 95039