Gasterosteus spinachia; Print; The sea stickleback (Spinachia spinachia); also known as the fifteen-spined or fifteenspine stickleback; is a species of stickleback which lives in benthopelagic and in brackish environments of the northeastern Atlantic Ocean. This species; the largest of the sticklebacks; grows to a length of 22 centimetres (8.7 in) SL. This species is the only known member of its genus Spinachia. It is of no interest as a commercial fish.