Samples of Corbicula fluminea (Muller) used for population analysis were taken from the Guangzhou Reach of Pearl River in 1981-1983, twice a year irregularly. The distribution of the species along the river reach was found to be discontinous. Theoretically, it is attributed to a negative binomial pattern calculated from the Morisita Index. The maximum density of the clam reached 7,500 inds./m2, however, the average density on the left river side is remarkely lower than on the right one (t = 2.6779; P<0.01)....