Changes in population characteristics of Mytella falcata (D'ORBIGNY, 1846) beds, an exploited tropical estuarine mussel

Abstract

Mytella falcata is a heavily exploited mussel from Brazilian mangrove estuaries. Population density, spatial dispersion, shell length, dry weight and biomass of mussels were estimated from two exploited beds and one unexploited bed. In the latter, mussels were smaller due to lower tidal inundation frequency and thus had little economic value. Mussels were continuously harvested from exploited beds until almost all individuals were removed and mussel spatial dispersion changed from aggregated to random as harvesting proceeded. Exploitation does not appear to be strongly size-selective as mean shell size and dry weight either remained high or increased during the harvesting season. In the unexploited bed, spatial dispersion remained aggregated but density decreased during the wet season, perhaps as a result of low salinity. The population characteristics studied are simple but potentially important indicators of overexploitation for use in mussel bed management.