 Assume that the number of fish in a pond is to be determined. Five labeled fish are added to the pond during the first visit (nB = 5).
<meaning-changed>  Assume that the number of fish in a pond is to be determined. Five labeled fish are added to the pond during the first visit (nB = 5).
 Assume that the number of fish (nA) in a lake. For the purpose of this example, assume all fish native to the lake are blue. On their first visit to the lake, an ecologist adds five yellow fish (nB = 5).