Sprattus sprattus


Otolith description
The general shape of the otolith is ovally pointed. The sulcus is straight and runs over the whole length of the otolith and is open at both sides. The sulcus is not well developed and ostium and cauda can not be distinguished. The surface of the sulcus is smooth but at the ostium side a small depression is visible. The surface of the inside is smooth, whereas the margins are a bit irregular. Both anterior and posterior margins are indented at the ostium and cauda respectively, though this is not always very clear at the cauda. The posterior end is pointed at the ventral side. The outside of the otolith is smooth. The rostrum of the otolith is distinct and rounded; the antirostrum is well visible and rounded. The otolith is thin and flat at both the inside and outside. Sprat is the smallest of the clupeiformes and otoliths are not larger than 2.5 mm.
Sprat otoliths are difficult to distinguish from other clupeiformes. Typically, the posterior and ventral margins tend to be at an angle smaller than 90° with each other; this angle is about 90° in herring Clupea harengus and larger than 90° in twaite shad Alosa fallax. Herring otoliths are no as round and the sulcus is better developed. The rostrum and otolith length-width ratio are larger in herring otoliths. Otoliths of pilchard Sardina pilchardus have a well-developed pointed rostrum and the posterior end is not indented and more rounded. The otolith length-width ratio is also larger in pilchard otoliths. The otoliths of twaite shad often have between the rostrum and antirostrum another protruding element, and the margins are straighter compared to the margins of sprat otoliths. Anchovy Engraulis encrasicolus otoliths have a closed sulcus and ends at the centre of the otolith. The rostrum is more pointed in anchovy otoliths.
When eroded the sulcus becomes less distinct and the margins, rostrum and antirostrum are smoothed. Often the rostrum is missing after the otolith has gone through the digestive tract of an animal.
Otoliths of small sprat are more round instead of oval. The ventral margin is already jagged. The rostrum is less pointed but not well developed.

Fish length and distribution
Sprat can grow up to 16 cm. Sprat is a common small pelagic, schooling roundfish (SPRASPRA.TIF) that is mostly found in inshore waters. It is found in deeper waters during winter and like herring has a daily cycle and comes to the surface at night to feed. It spawns in spring and summer (Wheeler, 1978, Nijssen and De Groot, 1987, Muus et al., 1999).
Sprat is found in the inshore waters of the NE Atlantic, North Sea and Baltic.

Sample origin
Mainly fyke catches but larger specimens are also caught in the Southern North Sea.