Clupea harengus


Otolith description
The general shape of the otolith is ovally pointed. The straight sulcus runs over the whole length of the otolith. It is open at both sides but this is not always clear at the posterior end of the otolith. The sulcus is well developed but ostium and cauda cannot be distinguished. The surface of the sulcus is irregular at the ostium side. The surface of the inside is smooth with some irregularity at the edges of the sulcus in some specimens. The dorsal margin is somewhat irregular and the ventral margin is lobed especially at the posterior end. Both anterior and posterior margins are indented at the ostium and cauda respectively, but otherwise smooth. The outside of the otolith is smooth. The rostrum of the otolith is very distinct and straight at the end or rounded. The antirostrum is large and pointed. The otolith is thin and flat, both at the inside and outside. Herring has the largest otoliths of the clupeiformes, otoliths larger than 5.5 mm are always of herring.
Herring otoliths are often difficult to distinguish from other clupeiformes. In herring, the posterior and ventral margins tend to be at a 90° angle with each other; the angle is smaller than 90° in sprat Sprattus sprattus and larger than 90° in twaite shad Alosa fallax. Sprat otoliths are rounder and the sulcus is less well developed compared to herring otoliths. The rostrum of sprat otoliths is smaller. Furthermore the otolith length-width ratio is larger in herring otoliths. Sprat otolith length does not exceed 2.5 mm. The sulcus of pilchard Sardina pilchardus otoliths is less well developed than in herring. The rostrum is bigger and more pointed in pilchard otoliths. The posterior end is not indented in pilchard otoliths. Otoliths of pilchard can grow up to 4.5 mm. Otoliths of twaite shad have a sulcus that is less developed and otoliths often have between the rostrum and antirostrum another protruding element. Otolith length-width ratio is smaller in twaite shad. Otoliths of anchovy Engraulis encrasicolus have a less developed sulcus. The sulcus is closed and ends at the centre of the otolith. The rostrum is smaller and more pointed in anchovy otoliths. Also the posterior end of the otoliths is more pointed in anchovy.
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 juvenile herring are more round instead of oval and the ventral margin is still smooth. The rostrum is visible and pointed but not well developed.

Fish length and distribution
North Sea herring can grow up to 40 cm, Norwegian herring up to of 55 cm. Herring is a pelagic roundfish (CLUPHARE.TIF). It is found close to the bottom during daytime but comes to the surface at night to feed. Two different spawning races can be recognised in the North Sea: a spring spawning stock in the south and an autumn spawning stock in the west (Wheeler, 1978, Nijssen and De Groot, 1987, Muus et al., 1999).
Herring is found in the North Atlantic, North Sea and Baltic and is a common, schooling species.

Sample origin
Juveniles: Western Wadden Sea and fyke.
Adults: mainly from the fyke, some from western spawning stock.