We claim the ornamental design for a mermaid fish lure, as shown and described.
FIG. 1 is a front view of the present invention showing the mermaid fish lure with treble hooks attached to the back of the lure and attached to the bottom of the mermaid's fin, and including a spinner attached to the top of the mermaid's head; and,
FIG. 2 is a rear view of the present invention showing the mermaid fish lure with treble hooks attached to the back of the lure and attached to the bottom of the mermaid's fin, and including a spinner attached to the top of the mermaid's head.