Abstract
Diel and monthly variations in abundance, stage composition, biomass, production and feeding rates of the chaetognath Sagitta friderici were studied in the Cananeia Lagoon Estuarine System, Sao Paulo, Brazil. Plankton samples were collected at intervals of 4 h over several 24-h periods from February 1995 to January 1996. Sagitta friderici occurred throughout the year. Abundance of S. friderici showed considerable diel and monthly variations, ranging from 2 to 373 ind. m−3. During the low-salinity period of February and March, higher abundance was found when salinity was higher, but from May to January abundance did not show consistent pattern in relation to time of day and tidal cycle. Seasonal variation in total body length was related to temperature variations. Mean biomass ranged from 10.593 to 57.533 mgDW m−3. The daily production rate of S. friderici ranged from 0.009 to 4.488 mgC m−3 d−1. Sagittafriderici preyed mainly upon copepods (63.2%) such as Acartia (8.3%), Oncaea (7.4%) and Corycaeus (6.7%), among other prey. The daily mean feeding rate was 1.33 prey d−1 and it was related to the water temperature.
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