Clutch and egg size in the Japanese amphidromous goby, Rhinogobius sp.DA (R. brunneus, dark type), inhabiting small rivers in the southern part of the Kii peninsula were examined. Clutch sizes, ranging between 1043 and 4436, increased with increasing maternal standard length. Spawned egg volume ranged between 0.85 mm3 and 1.38 mm3, mean egg volumes being similar among the eight rivers sampled during the study. Rhinogobius sp.DA had a relatively larger egg and smaller clutch size compared to those of three other amphidromous Rhinogobius species inhabiting relatively larger rivers in the same region. Inter-specihic egg size variations among the four species appear to result in differing larval survival rates during their migration to the sea.
