DOWNSTREAM MIGRATION OF TAG -RELEASED JUVENILE CHINESE STURGEON (ACIPENSER SINENSIS)IN THE YANGTZE RIVER

1998-2002, 1752 thousands of juvenile Chinese sturgeon were released in the Yangtze River. Among them,77957 of two month old fingerlings(715) 1710cm Total Length) were tagged with Coded Wire Tags, and 400 fourteen month old juveniles(55) 98cmTotal Length)were tagged with both Coded Wire Tags and external silver tags. We sampled fishes after the release along theYangtzeRiver and costal areas. Within four years, 6400 fingerlings and 13 juveniles were captured.All captured juveniles weretagged and only 13 individuals of captured fingerlings were with tags.No significant difference between the wild fish and cultured released stock regarding the growth and the timing of appearance in the mouth of the Yangtze River. The average downstream migration speed of released juveniles was about 2816km/d(711) 10012km/d),with average distance between the release and recapture sites was 1,600km, ranging from 346km to 2, 459km. 4612% of recapture happened in the ocean. Based on the initial estimates, the contribution of culture released juveniles to the natural juvenile stock in the estuary of theYangtzeRiver is 21281% in 1999 and 01997% in 2000, respectively.Thewild stock of Chinese sturgeon is still themain sourceto maintain the population in theYangtze River.However, to release larger juveniles could contribute more to themaintaining of Chinese sturgeon population since the survival rate of them would be much higher than the fingerlings.