 In such situation, the following expression can be employed: where  RA is the ratio of the native-to-labeled fish in the lake , RB is the ratio of the native-to-labeled fish in the lot of nB marked fish which are added to the pond, and RAB is the ratio of the native-to-labeled fish captured during the second visit.
<meaning-changed>  In such situation, the following expression can be employed: where  RA is the ratio of the native-to-labeled fish in the lake , RB is the ratio of the native-to-labeled fish in the lot of nB marked fish which are added to the pond, and RAB is the ratio of the native-to-labeled fish captured during the second visit.
 In such situation, the following expression can be employed: where RA is the ratio of the native-to-labeled fish in the lake prior to the addition of marked fish; RB is the ratio of the native-to-labeled fish in the lot of nB marked fish which are added to the pond, and RAB is the ratio of the native-to-labeled fish captured during the second visit.