Rough Scad, Trachurus lathami
Rough Scad, Trachurus lathami, Juvenile. Fish caught from coastal waters off Long Island, New York, September 2023. Length: 13 cm (5.0 inches). Catch, photograph and identification courtesy of James Lafontaine, Long Island, New York.
The Rough Scad, Trachurus lathami, is a member of the Jack or Carangidae Family, that is also known as the Horse Mackerel and in Mexico as charrito garretón. There are twenty global members of the genus Trachinotus, of which seven are found in Mexican waters, three in the Atlantic and four in the Pacific Ocean.
The Rough Scad has a moderately compressed body that has a depth that is 26% to 30% of standard length. They are metallic blue to olive green in color dorsally and their lower two-thirds are paler ranging from white to silver. The caudal and dorsal fin margins are dark; all other fins are pale. They have a black area over the eyes on the upper edge of the gill cover. Their head has an equal lower and upper profile with large eyes that have fatty eyelids, and a small terminal mouth this is equipped with small teeth set in a single row on each jaw. Their anal fin has two standalone spines followed by 1 spine and 26 to 30 rays; their caudal peduncle is slender, and the caudal fin is deeply forked; their first dorsal fin has 8 spines; their second dorsal fin has 1 spine and 28 to 34 rays; and, their pectoral fins are long reaching past the anus. They do not have isolated finlets. A key to identification is their lateral line, which is arched in the middle and has well developed scutes on extending back mid-flank. Their body is covered with cycloid scales. They have 12 to 16 and 33 to 41 gill rakers.
The Rough Scad is a coastal schooling pelagic species found from the surface in the surf zone and near the bottom over the continental shelf to depths of 110 m (360 feet). They reach a maximum of 40 cm (16 inches) in length and 500 g (1 lb 1 oz). They are known to consume invertebrates, fish and fish eggs and in turn are preyed upon by large fish. The juveniles are known to take shelter within jellyfish to avoid predation. The Rough Scad is poorly studied with very limited information available about their lifestyle and behavioral patterns including specific details on age, growth, longevity, movement patterns, diet, habitat use, and reproduction.
The Rough Scad is a resident of all Mexican waters of the Atlantic Ocean including the Gulf of Mexico and the Caribbean.
The Rough Scad is very similar to the the Jack Mackerel, Trachurus symmetricus, from the Pacific. They are most likely confused with the Bigeye Scad, Selar crumenophthalmus (lacks arched lateral line), the Mackerel Scad, Decapterus macarellus (yellow-green caudal fin), and the Round Scad, Decapturus puntatus (lacks arched lateral line).
From a conservation perspective the Rough Scad is currently considered to be of Least Concern with stable, widely distributed populations. In some regions they are fished commercially with purse seines and sold for human consumption.