Resumen
Caprella scaura is an invasive amphipod, native to the Indian Ocean, which has already spread to several regions of the world, including the Mediterranean Sea. The present study reports the first occurrence of the species on fish farms cages in Greece, in the Pagasitikos Gulf. Specimens were collected from colonies of the bryozoan Bugula neritina. Basic aspects of the population dynamics of the species, such as the population structure, sex ratio, and size frequency were studied for 13 months and tested for differences between two depth levels (30 cm and 5 m). Population density was significantly different between the two sampled depths. All the demographic categories were present during the whole study period, indicating that the species follows a continuous reproduction pattern in the region. Males were typically larger than females, but females were more abundant in most samples. It seems that the species is well established in the region and is probably moving towards the northern parts of the Aegean Sea.