Bullhead
Cottus gobio
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All head and no tail, wedged under a stone — and the male guards the eggs himself.
A small, tadpole-shaped bottom fish with a broad flattened head, huge pectoral fins, bulging eyes set high, and no scales. The mottled brown colouring is superb camouflage against gravel. Also known as the miller's thumb, the bullhead lives under stones in the clean, fast, stony reaches of the Nith and its burns, and rarely moves more than a few metres in its life.
Behaviour
Bullheads are ambush predators, sitting motionless under a stone and lunging at passing invertebrates and small fish. They have no swim bladder, so they rest on the bottom and move in short darts rather than swimming freely. The male excavates a cavity under a stone, attracts a female to lay eggs on the roof of it, and then guards and fans the clutch alone until the young hatch.
When to see it
Quick facts
- Family
- Sculpins (Cottidae)
- Size
- Typically 8–12 cm
- UK status
- Protected under European habitats legislation
Photo by Woluhar, CC BY-SA 3.0, via Wikimedia Commons