Scad
Otolith description
The general shape of the otolith is ovally pointed. The sulcus runs straight over the total length of the otolith and is strongly curved and pointing down at the posterior. The sulcus is well-developed and deep and open at the ostium. Ostium and cauda are separated by a narrowing of the sulcus. The ostium is wider but much shorter than the cauda. The surface of the inside and outside is smooth. The dorsal margin is lobate. The ventral margin is rounded and smooth. The posterior margin is pointed in most specimens. The rostrum is well-developed and pointed, while the antirostrum is small and rounded. The inside is convex and the outside concave. The otolith is thick.
Scad otoliths may resemble those of bass Dicentrarchus labrax, which also have a sulcus pointing down posteriorly. Bass otoliths are much thinner, have a rounder rostrum and a ventral side which is more triangular.
When eroded the sulcus remains clearly visible. The rostrum is sometimes missing in otoliths that have gone through the digestive tract of an animal.
Otoliths of juvenile scad already have a strong curved sulcus, but the sulcus is not clearly visible. The rostrum is already pointed. The ventral and dorsal margin are slightly lobate.
Fish length and distribution
Scad can grow up to 50 cm. Scad is a common pelagic schooling fish (TRACHTRA.TIF) found in offshore waters. Juveniles can also be found in inshore waters. In winter scad is mostly found southerly of the North Sea, while in summer it is found as northerly as Southern Norway. Two spawning populations can be distinguished, in the Southern North Sea and the Bay of Biscay. Spawning takes place in May and June in the North Sea and slightly earlier in Biscay (Wheeler, 1978, Nijssen and De Groot, 1987, Witte et al., 1991, Knijn et al., 1993, Muus et al., 1999).
Scad is a common fish and found in the Eastern Atlantic and North Sea.
Sample origin
Juveniles: Southern North Sea.
Adults: Fyke.