Mediterranean Horse Mackerel

The Mediterranean horse mackerel has an elongated, compressed body (up to 60 cm (24 in) in length, common length 30 cm (12 in)) with a large head and projected lower jaw. The nostrils are small and close-set and the eyes are protected by a well-developed adipose eyelid. Its upper jaw, or maxilla, is also large and wide. Its body is a dusky color, blue to grey to black in color dorsally and on top of the head, while the lower two-thirds of the body is white to silver in color. Its caudal fin is yellow and it has a distinct black mark just posterior to the operculum. It has 36–41 gillrakers and the anal fin is preceded by two separate spines.

The Mediterranean horse mackerel is found in subtropical waters throughout the eastern Atlantic Ocean from the Bay of Biscay to Mauritania, as well as the Mediterranean Sea, the Aegean archipelago, the Black Sea, the Propontis or Sea of Marmara, and the southwestern Sea of Azov. Its latitudinal range extends from 49°N to 28°N and its longitudinal range extends from 13°W to 43°E. The subspecies T. m. mediterraneus is found in the Mediterranean Sea, while the T. m. ponticus subspecies, also called the Black Sea scad, is native to the Black Sea, the Sea of Marmara, and the Sea of Azov. T. m. ponticus is found in the territorial waters of every country bordering the Black Sea: Bulgaria, Georgia, Romania, Russia, Turkey, and Ukraine. Subspecies populations are not isolated and some limited migration between seas occurs. Hybrid offspring have been found in the wild. Its typical depth range is 5–250 m (16–820 ft), though it can be found as deep as 500 m (1,600 ft). It lives near the ocean floor, though it sometimes schools near the surface.

A marine species that prefers brackish water and subtropical temperatures, the Mediterranean horse mackerel is oceandromous, that is it migrates within its native bodies of water. It feeds primarily on sardines, anchovies, and small crustaceans. It shoals with other members of its genus, such as T. trachurus and T. picturatus. Like other mackerels, the Mediterranean horse mackerel's reproduction is oviparous. Its reproductive cycle is divided into three distinct stages, the prereproductive, reproductive, and postreproductive. The prereproductive stages occurs from January to April and the postreproductive stage occurs from September to December. During these periods, the gonads are much smaller than the reproductive stage. Mating occurs in the summer from May to August, during which testes and ovaries grow significantly in size. The ovaries become a dark orange color and eggs are visible on the surface. Embryonic development occurs in 24–26 hours. Eggs are pelagic and 0.71–0.92 mm (0.028–0.036 in) in length. Sexual maturity is reached at 2 years of age and around 16 cm (6.3 in) in length for both males and females. It is parasitized by the monogeneans Gastrocotyle trachuri, Pseudaxine trachuri, and Cemocotyle trachuri.