Particle size is not the only significant factor in the distribution of the benthic assemblages; environmental variables also play important roles. However, several variables are needed to establish accurate predictions and grain size, alone, was not adequate (McBreen et al. 2008). Sediment characteristics are recognized as a controlling factor, directly determining the presence and abundance of the soft bottom assemblages, and different species prefer various specific types of sediment. In other words, sediment characteristics are a crucial factor in species composition (Hily et al. 2008). Fresi et al. (1983) carried out a study on the structural analysis of benthic communities found in Parca Naturale della Maremma (the Central Tyrrhenian Sea) and reported a total of 14 amphipod species from the study area. However, the linear regression analysis between the variables of sediment and biological factors showed an important dependence of the community structure (Fresi et al. 1983). Fresi et al. (1983) reported a significant correlation between benthos formation and the distribution of the sediment characteristics. The same authors also mentioned that the communities in areas of sandy bottoms, which have a high species richness, are quite seperate from communities in areas where the bottom is sandy mud. According to Fresi et al. (1983), species diversity is low on bottoms with a high ratio of silt to clay. The same authors found that the highest ratio of sand was 96.4% and that of silt was 79.8%. In our study, the highest ratio of sand was detected as 99.59% in the Eceabat Station. Meanwhile, we found the highest ratio of silt to clay at the Dardanos station, with a value of 0.77%. Fresi et al. (1983) also reported the amphipods Corophium rotundirostre Stephensen, 1915, Hippomedon massiliensis Bellan-Santini, 1965, and Perioculoides longimanus (Bate and Westwood, 1868).