FEEDING HABITS OF SAGITTA FRIDERICI RITTER-ZAHONY IN COASTAL WATERS OFF BUENOS AIRES PROVINCE, ARGENTINA

Abstract

For the first time for local populations the diet of the dominant chaetognath Sagitta friderici was determined in coastal waters off Argentina. Samples were collected monthly in Estación Permanente de Estudios Ambientales (38° 28´ S, 57° 41´W, 48 m depth) from March 2000 through April 2001. Copepodite stages of the species Oithona nana, Oithona spp. and Calanoides carinatus and their eggs were the dominant prey. The food containing ratio varied from 7 to 35 % with a mean value of 21.71 ± 8.64 %. this index varied among the different months with no clear seasonal pattern. The number of prey eaten by the chaetognath was higher in March and July 2000 than in the other examied months; S. friderici consumed mainly prey 0.10-0.19 mm wide. A direct relationship was observed between the head width of the predator and the width of prey; S. friderici could be competing for food with the larvae of Engraulis anchoita.