Trophic habitat of the Pacific sharpnose shark, Rhizoprionodon longurio, in the Mexican Pacific

Abstract

The Pacific sharpnose shark Rhizoprionodon longurio is caught seasonally by inshore artisanal fisheries in the Mexican Pacific. Our study focuses on the feeding ecology of this shark species in the southern Gulf of California. The prey species obtained from stomach contents were identified and quantified, and variations between sexes and maturity stages were determined. A total of 98 stomachs were analysed during two periods (2000–2001 and 2003–2004); 64% of stomachs contained food. The trophic spectrum was composed of four cephalopod species, three crustacean species, and 13 pelagic and benthic fish species. According to the index of relative importance (%IRI), the fish Echiophis brunneus (IRI = 14.4%), Opisthopterus dovii (IRI = 12.2%) and Scomber japonicus (IRI = 9.6%) were the main prey items. Based on diversity values, IRI values and diet breadth, R. longurio is an opportunistic predator. The trophic position of R. longurio was above four in all categories, which indicates that this shark is a tertiary consumer.