Coinciding with fish-spawning season from April to May of 2006, we investigated two spawning grounds of Megalobrama hoffmanni in the Pearl River, at Qingpitang and Luopang, in order to understand their hydro-acoustics characteristics. We used a Simrad EY60 split-beam echo-sounder and employed both manual calibration and fishery information in order to recognize the echo signal of M.hoffmanni. Our results indicated the existence of a spawning aggregation of M. hoffmanni at the two spawning grounds. The aggregation scale in Luopang was higher. There was also a significant difference in the reproductive behavior at the two spawning grounds; the swimming speed of M. hoffmanni in Qingpitang was much slower than at Luopang. In light of these results, we postulate that habitat diversity is responsible for M. hoffmanni′s reproductive ecological diversity. Therefore it is important to maintain habitat characteristics in order to ensure the protection of this fish species.