Abstract: Chum salmon (Oncorhynchus keta) breeding population in Amur River immigrated from Okhotsk Sea in Russia runs into two geographic populations Amur population and Ussuri population when the salmon reach China border. In the past decade, China A- mur population developed strong nuptial colors very well, but few Ussuri population showed strong nuptial colors, even did not when they entered China. There were two groups faint color females (red chrominance a*〉13 ) and strong color females (red chrominance a*〈7)in Ussuri females whose breeding parameters were analyzed during 20th~29th of September in 2011 to evaluate the implica- tions of nuptial colors differentiation within a population in Ussuri River. It was found that the age, gonado-somatic index (GSI), egg diameter and weight, body length and body weight of the faint color females were all smaller than the strong color females very signifi- cantly (P〈0.01). The faint color females were found to have less absolute fecundity than the strong color females did significantly (P〈0.05), without significant differences in condition factor between the two groups. Correlations among reproductive parameters between the two groups revealed that the faint color females had lagged gonad development behind the strong color females, indicating that the strong color females shared higher reproductive fitness than the faint color females.

Key words: Ussuri river, Oncorhynchus keta, nuptial color, fitness