OBSERVATIONS ON THE FEEDING-HABITS OF THE SHARK HETERODONTUS-FRANCISCI GIRARD 1854 (CHONDRICHTHYES, HETERODONTIDAE), IN SAN-IGNACIO LAGOON,BAJA-CALIFORNIA-SUR, MEXICO

A total of 108 stomach contents of horn shark (Heterodontus francisci Girard, 1854) from San Ignacio Lagoon were analyzed. The samples were taken seasonally from January 1992 to February 1993. This species occu rred all year round, with low abundance in summer and fall. The index of relative importance (IRI) was used to determine the prey importance . The horn shark feeds mainly on benthic invertebrates, such as gastro pods (Lucapinella milleri and Calyptraea spp.), crustaceans (Callinect es bellicosus, Penaeus spp, and isopods), pelecypods (unidentified), s ipunculoids (Sipunculus nudus), cephalopods (Octopus spp.), as well as on small fishes (Syngnathus auliscus). This shark is a third-order co nsumer, because it is a predominantly carnivorous benthic species; it is a selective predator with nocturnal or crepuscular habits.