Tench
Otolith description
Otoliths of cyprinidae are very hard to determine to species level. The otoliths are all round with a remarkable horseshoe shaped sulcus that is directed downwards. The margins are jagged and indented at the ostium.
Five species have otoliths that tend to be somewhat different from the others. Tench Tinca tinca tends to be more oval shaped instead of round, compared to the other cyprinidae. On gudgeon Gobio gobio otoliths the margins tend to be smoother, probably because this is only a small fish and the otoliths are not well developed. Bitterling Rhodeus sericeus is the smallest of the cyprinidae and otoliths are not well developed either. They are smoother at the margins and the sulcus is hardly visible. Roach Rutilus rutilus otoliths have a posterior end that tends to be straight instead of round. The otoliths of rudd Scardinius erythrophthalmus are more jagged and pointed at the ventral margin.
Sizes of otoliths:
gudgeon, bitterling: <2,5 mm
silver bream, roach, rudd: <8 mm
tench, bream, ide: <10 mm
carp: otoliths > 10 mm are always carp otoliths
When eroded the otoliths of all cyprinidae are smoothed, but the sulcus remains visible.
Cyprinidae are a family of fish that have well-developed pharyngeal teeth and chewing pads. These are very useful for specific identification of the different fish species (Wheeler, 1978, Veldkamp, 1994, 1995); also because these fish remains are less vulnerable to erosion by the stomach acid.
Pharyngeal teeth description
Tench pharyngeal teeth have only one row of 4 to 5 teeth. The teeth have a small depression on top. (Photograph of pharyngeal teeth not yet available)
Chewing pad description
The chewing pad of tench is oval shaped, with the widest point quite far dorsally. The surface of the inside is smooth. The pad is rounder, more droplet shaped compared to the bream chewing pad. The ventral margin is straight or indented.
Fish length and distribution
Tench can grow up to 70 cm. Tench is a common freshwater fish that is found in still and densely vegetated waters. It spawns in shallow water in late spring and early summer (Wheeler, 1978, Nijssen and De Groot, 1987).
Tench is found in fresh water bodies throughout Europe.
Sample origin
Northern part of the Netherlands.