The narrator dreams of ghosts of salmon because he feels out of place in his current environment and wants to get in touch with his Native American heritage.

Truth be told, he's always felt out of place wherever he's been in life. That includes the reservation on which he grew up, a place characterized by poverty and lack of opportunity. Even after leaving the reservation, the narrator still felt out of place, if anything even more so.

It's only in his wishes and dreams that he can truly feel that he belongs somewhere. There, he can live closer to the river, a natural feature of the landscape that has deep spiritual significance for his people. He can also return to the falls where ghosts of salmon jump. Once upon a time, the narrator's ancestors fished in these waters, but like so much of what once belonged to Native Americans, they were taken from them by white men.

The narrator's dreams and wishes hark back to a simpler time, a time when his people were free to roam across the land of their ancestors without needing to worry about it being taken from them.