Geographic differences in the diet and isotopic niche of Octopus hubbsorum (Cephalopoda: Octopodidae) in the Mexican Pacific

Abstract

Octopus hubbsorum is an important fisheries resource in the Mexican Pacific and a link among different trophic levels due to its ecological role as both predator and prey. In this study, the spatial variations in the diet, isotopic niche and trophic position of O. hubbsorum were determined by analysing digestive contents along with carbon and nitrogen stable isotopes. Octopuses were sampled from four locations, three in the Gulf of California ecoregion and one in the Mexican Pacific transition ecoregion. The diet of O. hubbsorum consisted of 11 major taxonomic groups. Crustaceans were the most important prey, although some individuals consumed high proportions of polychaetes, eggs and cephalopods. The stable isotope values showed high variation (−15.86 to −13.76‰ δ13C; 14.80–17.23‰ δ15N), reflecting signals of the base of the food web at the four locations. Differences in trophic positions and isotopic niches confirm the role of this species as a generalist predator, as it can shift among alternate food sources according to local availability. Overall, our results suggest that O. hubbsorum has a similar ecological role at all locations as a predator of crustaceans and, to a lesser extent, of molluscs and fish.