What does the line "The old man returned to sleep and dreamt his usual dream of lions at play in beaches of Africa" in The Old Man and the Sea mean?

Similar quotes of Santiago dreaming of lions recur throughout the text, such as:

He only dreamed of places now and of the lions on the beach. They played like young cats in the dusk and he loved them.

The novel ends with this line:

The old man was dreaming about the lions.

The lions symbolize youth, vigor, and happiness to the old man, who associates lions with his younger days in Africa. It is significant when he dreams of them, for this shows he is happy at those times. He does not fear the lions—who represent nature's strength—but loves them as he loves the natural world and the sea beside which they play.
It is especially significant that the novel ends with Santiago dreaming of his beloved lions. This suggests that he has been invigorated rather than defeated by the sea and his struggle with the sharks over the fate of the marlin. The sharks might have "won" in stripping the marlin clean, but they have not broken the old man's spirit, because he still dreams happily of his lions.