Plate XIV
Bullhead
Cottus gobio
No minimum size — release fish you won't keep.
The bullhead, more widely called miller's thumb, is a small bottom fish of at most about 15 to 18 centimetres, living in clean, oxygen-rich and cool flowing waters and regarded as an indicator species for good water quality. In the Franconian Saale it is especially favoured by the cooler, fast-flowing and well-structured sections of the Rhön and uplands character. Lacking a functional swim bladder, it is a poor swimmer that, nocturnal and well camouflaged, hops jerkily across the stony bottom.
How to identify it
Reliably recognised by three features: the broad, flat, frog-like head, the very large pectoral fins spread out like a fan or sail, and the scaleless, smooth and slippery skin.
Look-alikes
It is considered practically unmistakable; the safest distinguishing feature against the similarly small bottom fish is the absence of barbels, since the stone loach (six barbels) and the gudgeon (two barbels and clearly scaled) always bear barbels, the bullhead never.
Local note: Strictly protected Habitats-Directive species and an indicator of clean water – please release carefully.
Tip
As an angling target it is insignificant and moreover protected, so an accidental by-catch should be returned quickly and carefully with wet hands, mindful of the gill-cover spine.
This profile is provided without guarantee; biological details and especially closed season / minimum size must be checked against the current AVBayFiG and your permit before relying on them. Rules & closed seasons.