Preliminary survey of Porcellanidae larvae at the Piraquê-açú river system estuary, Aracruz, Espírito Santo State

Abstract

Composition and abundance of Porcellanidae larvae were studied at the Piraquê-açú and Piraquê-mirim estuarine system, in the city of Aracruz, state of Espírito Santo. These larvae were collected monthly (between April and July 2003) in eight sampling locations, with 4 locations at the Piraquê-açú River and 4 at the Piraquê-mirim River. Samples were collected using a plankton net with 50cm mouth opening and 200 micron mesh size. Abiotic factors (e.g. temperature and salinity) were also analyzed in situ at each sampling location and water was sampled with a Van Dorn bottle to analyze chlorophyll-a concentration. Two species (Petrolisthes armatus and Pachycheles monilifer) and one genus (Megalobrachium) were found. Piraquê-açú River showed a greater variation in salinity among the diferent sampling locations and a higher abundance of larvae. The highest larvae abundance was registered in April. P. armatus and Megalobrachium sp. were found at the zoea I and zoea II stages. Significant differences between species (and their developmental stages), sampling locations and rivers were not observed. Diffences were observed only between larvae abundance and months. Spearman’s correlation evidenced significant correlation between larvae at the zoea I stage and chlorophyll-a concentration, indicating that early life stages feed mainly on phytoplankton.