RESUMEN
The goals of this study were to describe the diet and estimate the trophic level and food selection of Jenyns's sprat Ramnogaster arcuata, one of the common fishes in the Bahía Blanca estuary in Argentina. The copepods Acartia tonsa [53·7% index of relative importance (I(RI))] and Eurytemora americana (13·4% I(RI)), the mysid Arthromysis magellanica (13·9%I(RI)) and the small shrimp Peisos petrunkevitchi (8·2% I(RI)) were the most important food items for this species, and its diet exhibited monthly variability with respect to the principal prey categories. The zooplankton species in the study area consisted of 32 taxa. Acartia tonsa was the most abundant species [54% individuals (N) m(-3)], followed by Balanus glandula (13·8% N m(-3)) and E. americana (10·1% N m(-3)). The rest of the zooplankton groups represented <3% N m(-3). The most preferred items throughout the year were A. magellanica and Idotea sp. The trophic level value estimated was 3·1.