Effects of age, maturity stage, sex and seasonality on the feeding strategies of the diamond stingray (Hypanus dipterurus) in the southern Gulf of California

The diet of the diamond stingray (Hypanus dipterurus) was quantified based on individuals collected monthly from October 2013 to December 2015 on Espiritu Santo Island in the Bahia de La Paz, Mexico. Of the 473 stomachs analysed, 211 (44.6%) contained food. Analysis of the prey-specific index of relative importance indicated that the diet of H. dipterurus was based on infaunal and epibenthic invertebrates, especially the bivalve Solemya spp. (42.2%) and the stomatopod Nannosquilla raymanningi (7.7%). Statistical analyses of the diet considering sex, age, maturity stage and interactions between sex, age and season indicated that older females consumed more polychaetes in the cold (November–April) season and that younger females consumed more stomatopods and bivalves in the warm (May–October) season. The feeding strategy of the species is specialised on three prey categories (bivalves, polychaetes and stomatopods), with low trophic niche breadth values. The calculated trophic level indicated that the diamond stingray is a secondary consumer and mesopredator. We conclude that the diamond stingray does not maintain a redundant trophic function with sympatric elasmobranchs in the study area, and is therefore likely a key prey density-regulator functioning to link energy derived from lower to upper trophic levels within the southern Gulf of California.