Temporal and sexual effects in the feeding ecology of the marbled sand skate Psammobatis bergi Marini, 1932

Abstract

Temporal and sexual effects in feeding ecology were examined in the marbled sand skate (Psammobatis bergi). Of 137 stomachs analysed, 130 (95%) contained food. Among these, >50% contained between 2 and 4 items, with a maximum of 18 prey items found. Thirty taxonomic levels of prey items were identified: 18 crustaceans, 5 polychaetes, 3 molluscs, 3 teleosts, and 1 chondrichthyan. Coenophthalmus tridentatus and unidentified Brachyura were the dominant prey items by number, frequency of occurrence and index of relative importance (IRI). Libinia spinosa was the dominant item by mass and third most important by %IRI. Psammobatis bergi consumed mostly brachyurans and showed little variability in overall mean prey importance, hence, only a small number of stomachs was needed for a precise description of its dietary composition. There was no interaction between season and sex in the diet composition of P. bergi and there were no differences between the diets of males and females during winter and spring. However, a seasonal pattern was found. The most important prey in spring was C.tridentatus by number and L.spinosa by mass whereas in winter the most important prey was Peltarion spinosulum. The temporal pattern indicates that P. bergi probably modifies its diet in response to prey abundance.