Faculty of Bioresources, Mie University, Tsu 514-8507, Japan
To evaluate the validity of indicators for egg quality assessment of Japanese whiting Sillago japonica, such as floating rate, neutral buoyancy salinity (NBS), and total egg osmorality, these variables were measured on the eggs during the spawning season in 1995 and 1999, then the relationships between these variables and viable hatching rate of the eggs were examined. No correlation was detected between floating rate and hatching rate in both years (r=−0.03 and r=−0.04). In 1995 hatching rate significantly correlated with both NBS (r=−0.87) and osmorality (r=−0.79), but not in 1999 (r=−0.04 and r=−0.12). These arranged data in both years showed that the eggs with NBS higher 28PSU and osmorality higher 480mOsm/kg were low in hatching rate. It is, therefore, concluded that both NBS and osmolarity are the indicators available for assessing egg quality of S. japonica.