232 



BULLETIN OF THE BUKEAU OF FISHERIES 



87. Mackerel scad (Decapterus macarellus Cuvier and Valenciennes) 



Jordan and Evermann, 1896-1900, p. 909. 



Description. — The scads are easily recognized among pompanos by the presence 

 of a small detached finlet between the second dorsal and the base of the caudal 

 fin 97 with another similar to it behind the anal. Furthermore, they are more 

 slender than most other pompanos, being only about one-fifth as deep as long, 

 and fusiform like a mackerel, but the great length of the second dorsal fin and 

 the fact that there is only one dorsal and one anal finlet would separate a mackerel 

 scad from a mackerel at a glance. The nose of the scad is blunter, its snout shorter, 

 its mouth smaller, and its preniaxillary bones are protractile. The triangular first 

 dorsal fin (8 spines) originates over the middle of the pectoral. The second dorsal 

 (about 34 rays) is separated from it by only a very short space and extends back 

 nearly to the base of the caudal. The anal is sinular to the second dorsal in form 

 but shorter (34 to 27 rays), originating about under the seventh or eighth ray of 

 the latter, and it is preceded by 2 short stout spines. The ventrals are shorter 

 than the pectorals and below them. The tail of the scad is less deeply forked than 



/ \ M 



Fig. 107.— Mackerel scad (Dccapterus macarellus) 



in most pompanos. In place of fleshy keels on the caudal peduncle, the posterior 

 half of the lateral line is armed with a series of about 31 keeled shields, largest on 

 the peduncle, and all of them much larger than the ordinary scales — a very notice- 

 able character. 



Color. — Described as slate blue or leaden above, silvery below, with a small 

 black spot on the margin of the gill cover and with the axil of the pectoral black. 

 We have not seen it alive. 



Size. — Maximum length about 1 foot. 



General range. — Warm parts of the Atlantic, rarely straying northward to the 

 Gulf of Maine and to Nova Scotia. 



Occurrence in the Oulf of Maine. — A single specimen caught with smelt in 

 Casco Bay, Me., in 1920 is the only Gulf of Maine record, though it has been taken 

 at Canso, Nova Scotia, but being common in the autumn about Woods Hole, where 

 as many as 10 barrels have been taken from one trap haul, it would not be sur- 

 prising to find it north of Cape Cod. 



»' A second scad, the "round robin" (Decapterus punctatw), similarly characterized, is known as far north as the Woods 

 Hole region. It has 40 or more scutes or shield scales on the lateral line, instead of only about 30 or 31; its jaws are toothed, and it 

 is spotted along the lateral line, characters that separate it from the mackerel scad. 



