Differential use of food resources by dominant fish of San Ignacio Lagoon, Baja California Sur, Mexico.

Abstract

The use of food resources in five of the most abundant fish species (Occidentarius platypogon,Cynoscion parvipinnis, Menticirrhus undulatus, Trachinotus paitensis and Heterodontus francisci) in San Ignacio Lagoon, Baja California Sur, Mexico is described. Prey composition, seasonal changes, diet breadth, trophic diversity and trophic overlap were analyzed. Forty nine prey items were identified, grouped into six taxonomic groups: crustacea, molluska, osteichthyies, anellida, equinodermata and sipunculida. Crustaceans and mollusks were the most important items recorded, representing over 75% of the identified prey. The crustaceans Callinectes bellicosus, Penaeus californiensis, Squilla spp., megalop larvae ofportunids and the mollusks Donax spp., Lucapinella milleri, Anachis spp., and Bittium spp. were the most important prey in the fish species analyzed. Differences in the prey composition and seasonal changes were observed, as well as seasonal changes in the diet breadth. All the predators examined had low percentages of breadth of diet, being characterized as opportunists with low levels of trophic diversity. There was only one case of higher prey overlap between O. platypogon and C. parvipinnis. We concluded that food resource partitioning is very important only in those fish species with higher overlap in their diets. Differences in bucal morphology seem related to prey selection.