Nine-spine sticklebacks: Britain’s tiny but mighty freshwater fish

Male nine-spine sticklebacks build nests and protect their young from predators. Photograph: Andrew Darrington/Alamy

The nine-spine stickleback, Pungitius pungitius, is Britain’s smallest freshwater fish and one of the toughest, able to withstand oxygen-poor water and a variety of temperatures.

Like its more numerous cousin, the three-spine stickleback, the males play a significant role in the breeding process. They build a nest and, once the female has laid her eggs, the males protect them from predators.