Answer:
In this case, the fish are considered rival goods, because if Becky, her dad, or any other person catches one fish, this person keeps it, preventing other people from catching and consuming it.
In this case, the river in town is non-excludable, while the stream at Becky's property is excludable. The river in town does not exclude anyone from fishing, while Becky's family probably does not allow anyone other than family to fish in the stream located at their property.