This is a small fish sometimes called a ‘Tiddler’, with 2 to 4 dorsal spines (usually 3 spines), just in front of the dorsal fin. Larger fish are discouraged from swallowing Sticklebacks because of those dorsal spines which can be sharp and locked erect. A favourite quarry of children with fishing nets in small pools, they hover and dart about in open water and are usually quite easily spotted and caught. It has a torpedo-shaped body which narrows towards the tail, which is either mottled brown or greenish, being silvery underneath. During the breeding season the male has a red underbelly and a bluish dorsal sheen. Length 4 to 7 cm.
It is a fierce carnivore which feeds mainly on invertebrates, but it will also eat tadpoles. The male attracts the female to courtship with his bright red underbelly and by doing a courtship dance. He will build a nest with vegetation in which the female will lay up to 400 eggs. He will then defend the nest from predation, and will fan the eggs to ensure a plentiful supply of oxygen. After the eggs have hatched 4 weeks later he will protect the small fry and teach them how to defend themselves against predation. They can live up to 5 years.
It can live in brackish water, freshwater or salt water environments, including freshwater rivers and streams, freshwater ponds, lakes and ditches, and in coastal habitats like estuaries and harbours. A common and widespread species throughout Britain.
Photographs taken August 2015, country park pool, Staffordshire.