POPULATION-DYNAMICS OF THE DATE MUSSEL, LITHOPHAGA-LITHOPHAGA (L., 1758) (BIVALVIA, MYTILIDAE), IN THE EVOIKOS GULF (GREECE)

Changes with time in a Lithophaga lithophaga population, spatial distr ibution, size-frequency distribution and recruitment were studied. The population was homogenous, without statistically significant differen ces, down to a depth of 6 m, the depth to which sampling was carried o ut. Population density showed periodic variations over the year and ch anged as the gradient of the substratum increased. Dispersion indices indicated that individuals were distributed randomly in clumps during the period of recruitment at different depths. Juveniles, up to a leng th of 4 mm, formed the highest percentage of the population. Larvae se ttled at a length of > 260 mu m, and individuals reached a length of 3 5 mm by the end of their first year. The appearance of newly settled i ndividuals occurred two months after the maximum occurrence oi larvae in the water. High percentages of settled spat were first observed in early winter at a depth of between 0-3 m although, later, higher perce ntages were found at 3-6 m depth.