Bullhead

• It has no swim bladder, which suits its life pressed against the riverbed.
• The male guards and actively fans the eggs throughout incubation.
• When food is short the male may eat his own clutch.

Skeleton type

Vertebrate - internal bony skeleton (fish)

Habitat and environment

Fast, cold, well-oxygenated rivers and the rocky shores of cold lakes across much of Europe, from Scandinavia to Italy

Birth weight

Eggs laid under stones; a tiny larva on hatching

Size at birth

A tiny larva on hatching; the male tends and defends the eggs until they hatch

Sexual maturity

Not precisely known (maturity is reached in the first or second year)

Gestation / incubation

Several weeks of egg development, watched over and actively fanned by the male

Litter / clutch size

100 to 500 eggs per clutch

Sources consulted: The Wildlife Trusts · Natural England (Ecology of the Bullhead) · FishBase · Website of Everything · Grokipedia · Wikipedia (European bullhead) · Fishipedia

Best time: All year round in cold, well-oxygenated rivers and streams; by day it stays under stones and is found only by lifting them carefully.