Abstract: The resources of migratory spawning groups and changes in population structure were surveyed in a total of 9160 statistical samples of chum salmon Oncorhynchus keta collected in Ussuri River from October 4 to October 21 in 2010.The results showed that water temperature and dissolved oxygen have a great impact on the quantity of spawning chum salmon daily.Two peaks were observed with an average of 64 individuals in a daily single boat catch.The individuals with body length of 55~65 cm were found to account for 74% in the group,with very similar ratio of male（36.82%） to female（36.58%） for the individuals with body length of 55~60cm.For the individuals with body length of less than 55 cm,however,the male individuals（27.17%） had higher proportion than the females（12.75%） did.There was higher proportion in the female（48.61%） than in the males（34.25%） in the chum salmon with body length of over 60 cm.The individuals with body weight of 2 000~3 000 g comprised of 57% in the group surveyed,and for the individuals with body weight of over 2.500 g,there was higher proportion in the females（61.73%） than in the males（46.06%）,with the ratio of female to male = 1.09：1.In the group of the chum salmon with body weight of above 2 500 g the females were shown the maximal proportion（36.06%）,followed by in males（28.8%） with body weight of less than 2.500 g.The chum salmon production in this year was the maximum in the past 15 years compared with the past data,indicating that the overall amount of resources presents an increasing trend year by year,but that the fish become smaller in size,with predominant females.

Key words: Ussuri River, Oncorhynchus keta, population structure