Loligo vulgaris is a commercially important squid throughout the Mediterranean region and is a candidate species in biomedical and aquaculture research. Some loligo species (L. opalescens, L. forbesi, Sepiteuthis lessoniana) have now been cultured through some successive generations in closed, recirculating seawater systems. The effects of salinity on hatching European Squid (L. vulgaris Lamarck, 1798) eggs were investigated during November 2004. The egg capsules were incubated directly in salinity of 32, 34, 36, 38, 40, 42 and 37 g L-1 (control group) at 19.8 degrees C (SD 1.2 degrees C), and a photoperiodicity of 12 h light:12 h dark for 16-23 days before hatching. In all treatments, the eggs were developed and hatched normally after 16-22 days at 32 g L-1, 17-22 days at 34, 18-21 days at 42 g L-1, 18-22 days at 36 and 40 g L-1, 19-22 days at 37 g L-1 and 19-23 h at 38 g L-1. In the experiments, the highest hatching rate and hatching success (HS) of the eggs were obtained at 38 g L-1 (hatching rate: 100% (SD 0%) and HS: 96.7% (SD 3.5%)) and the lowest hatching rate at 42 g L-1 (hatching rate: 3% (SD 6%) and HS: 0%). Dorsal mantle lengths (DML) of new hatchlings ranged from 2.08 to 2.80 mm. The present study showed that salinity affects the hatching rate and HS of eggs and first hatching time and DML of paralarvae in L. vulgaris. The squid eggs at stage 11 (I) can tolerate 5 g L-1 reduction and 3 g L-1 increase in salinity.