Notes on feeding of chaetognatha in Guanabara Bay, Brazil

Abstract

A preliminary analysis, by means of the gut content, of the diet of Sagitta friderici and Sagitta enflata occurring in Guanabara Bay was carried out. The samples were collected at different times over a 4 day period in September 1995, during vertical tows with a conical net of 200 μm mesh size at a fixed station (30 m depth). In total, 1000 individuals were examined. Copepoda were the numerically dominant group of prey of S. friderici and S. enflata (67.2 and 74.6%, respectively); both species behave as opportunistic carnivores, feeding mainly on the more abundant copepod species throughout the water column. Adult individuals of S. friderici and S. enflata (stages III and IV) seem to have food requirements different from juveniles: adults fed on other items (chaetognaths, crustacean larvae, hydromedusae and luciferidae), and the food containing ratio (FCR) was higher in individuals of stage III. In general, only one prey per gut was registered. Chaetognaths may have chosen their prey in relation to their size, since the size of the prey was proportional to the size of their predators. Feeding intensity (NPC) was higher in individuals collected during the night periods.