Abstract: A bobber is provided for a fishing line which provides a light signal when a fish strikes. The bobber includes an electrical circuit for the light which has a position-sensitive switch that is activated when the bobber is rotated about its center of gravity due to the striking of a fish. The battery in the bobber serves as a ballast to normally hold the bobber in upright position and posts extend from opposite sides of the bobber which are attached to the fish hook and fishing line and act as moment arms to rotate the bobber when a fish strikes.