Sea stickleback
(Spinachia spinachia)

Spinachia is a monospecific genus of ray-finned fish belonging to the family Gasterosteidae, the sticklebacks. The only species in the genus is Spinachia spinachia, the sea stickleback, fifteen-spined stickleback or fifteenspine stickleback, a species 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. 

The fifteen-spined stickleback is an elongated fish with a long slender snout, an elongated caudal peduncle about one-third of the total length, and a fan-like rounded caudal fin. The anterior dorsal fin consists of a series of fourteen to fifteen small, widely separated spines. The posterior dorsal fin and the anal fin are aligned and are similar in size and shape and located immediately anterior to the caudal peduncle. The pelvic fins consist of spines.

This fish is brownish-yellow with indistinct dark markings and a silvery belly.

The fifteen-spined stickleback is native to coastal waters in the northeastern Atlantic Ocean where it lives among bladderwrack and eelgrass.