Abstract: Through comparing the body size and head size among juveniles and female and male adults, the sexual dimorphism of Shinisaurus crocodilurus was studied. There was a significant difference in the ventral color of head and breast between the adults, i.e., vivid red or light blue for the males, and light yellow or light red for the females. The head size (including head width (HW) and head length (HL)) of the males were significantly larger than those of the females (HL, P<0.001; HW, P<0.001), and the abdomen length (AL) of the males was significantly shorter than that of the females (P=0.018). However, the snout-vent length (SVL) and tail length (TL) between the males and females were not significantly different (for SVL, P=0.193; for TL, P=0.22). The increasing rate of HL with SVL for the juveniles was higher than that for the female adults (P=0.021), whereas the HW was not significantly different between the juveniles and female adults (P=0.545). The head size of both the juveniles and the male adults increased with SVL at the same rate (for HL, P=0.252; for HW, P=0.441). When the SVL was kept constant, the HW of the juveniles was larger than that of the female adults (P<0.001), and the HL of the juveniles was larger than that of the male adults (P<0.001), but the difference of HW between the juveniles and the male adults was not significant (P>0.05). The results indicated that partial sexual dimorphism existed in S. crocodilurus.

Key words: East China Sea, Harmful alga bloom, Prorocentrum dentatum