Thegrowth of the bivalve Abra segmentum (Recluz, 1843) in two Mediterranean lagoons

Abstract

1 - The growth of Abra segmentum was studied for nearly one year in two Mediterranean lagoons with different degrees of communication with the sea. 2 - Tsopeli, situated in Amvrakikos Gulf (Ionian Sea), is a brackish-water lagoon, with restricted water circulation, relatively isolated from the open sea. Vivari is situated in Argolikos Gulf (Aegean Sea), and has better communication with the sea. Both lagoons are shallow with muddy bottom and both are used for the extensive culture of fish. 3 - Differences in the populations of A. segmentum were found regarding intensity of recruitment and growth in the two lagoons: recruitment was higher and survival lower in Vivari, while growth was better in Tsopeli. 4 - Length frequency histograms showed that larger body-size classes prevailed in Tsopeli, as opposed to Vivari where smaller individuals dominated. Mean individual size of A. segmentum was higher in Tsopeli throughout the year. 5 - Predation may be important in structuring the populations, however, comparison with findings in the literature suggest that the degree of communication with the sea is a more important factor controlling growth of A. segmentum.