Bullhead
Otolith description
The general shape of the otolith is ovally pointed. The sulcus runs almost straight over to of the length of the otolith. The sulcus is not well developed, shallow and open at the ostium. Ostium and cauda are not easy distinguishable and separated by a slight narrowing of the sulcus. The ostium is wider than the cauda. The surface of the inside is smooth, while the outside surface is irregular. The ventral margin is straight or slightly rounded, but smooth. The dorsal margin is rounded and smooth but may be strongly indented in smaller specimens. The rostrum is well developed and pointed, while the antirostrum is small and rounded or indistinct. The anterior margin is slightly indented between the rostrum and antirostrum. The posterior margin is pointed. The inside is convex and the outside concave. The otolith is thick. Otoliths do not exceed 5 mm in length.
Otoliths of bullhead are difficult to distinguish from marine cottidae, such as bull-rout Myoxocephalus scorpius and sea scorpion Taurulus bubalis (but origin of samples may provide a clue for identification). Otoliths of bull-rout are the largest of the three, otoliths >5 mm are always of bull-rout. Bullhead otoliths are longer and more pointed (particularly at the posterior end) than bull-rout or sea scorpion otoliths, but small specimens of the latter may also be pointed. The sulcus is less well developed and not deep. The antirostrum is less distinct than in bull-rout otoliths. Otoliths of bull-head are irregular on the outside instead of smooth.
When eroded the sulcus becomes indistinct. The rostrum and posterior end are smoothed.
In samples sometimes the preoperculae of cottidae can be found. These can be useful for determining the species of cottidae. Bullhead has only one not well-developed spine on the preoperculum. The preoperculum of bull-rout has two relatively short but straight spines which are pointing more upwards than backwards. Sea scorpion has one long slightly curved spine on the preoperculum. The spine is pointing more backwards than upwards.
Fish length and distribution
Bullhead can grow up to 17 cm. Bullhead is a fresh water living fish (COTTGOBI.TIF) found in streams and lakes with rocky bottoms. It hides between the rocks at daytime and becomes active at night. It spawns from March to May and the eggs are deposited under stones (Wheeler, 1978, Nijssen and De Groot, 1987).
Bullhead is found in the streams and lakes of Western and Central Europe.
Sample origin
Lake IJssel.