The Collaborative International Dictionary of English v.0.48:
mackerel scad \mackerel scad\, mackerel shad \mackerel shad\n. (Zool.) A small silvery fish (Decapterus macarellus) found from Nova Scotia to Brazil. [WordNet 1.5]WordNet (r) 3.0 (2006):
mackerel shad n 1: small silvery fish; Nova Scotia to Brazil [syn: mackerel scad, mackerel shad, Decapterus macarellus]