Population dynamics of two caprellid species (Crustaceae: Amphipoda: Caprellidae) from shallow hard bottom assemblages

Abstract

The community structure of caprellids associated with shallow hard bottom assemblages was studied in four locations around Pagasitikos Gulf, western coast of the Aegean Sea. Samplings were carried out every 3 months from April 2009 to April 2010. Samples were collected by scraping off the hard substrate, using 400-cm(2) handmade quadrate samplers. Water temperature, pH, salinity, dissolved oxygen and sea current velocity were measured in situ. Two caprellid species were found, Caprella acanthifera and Phtisica marina, with a clear dominance of C. acanthifera at all locations. The abundance of both species followed a seasonal pattern with a peak in spring or summer and a decline in winter. Lower abundances were detected at the locations with high current velocity and higher abundances at the locations with low water flow speed. This is an indication that the species might prefer areas with low hydrodynamism. Strong sexual dimorphism in body size was observed for both species, and the sex ratio was 1:1 throughout the samplings. It appears that reproduction for both species is continuous throughout the year, with a possible major breeding event in winter.