In enumerating salmon spawning population by the tag-recovery method, the error caused by the emigration of the tagged fish into the non-statistical area and the misjudgement of the tagged fish as untagged, which is caused by bear predation, appear to give a bias to the estimate of population size. Efforts were made in the present study to remove such bias by estimating population size under certain assumtion and by introducing a correction equation for the sample tag-ratios.