Phylum: Chordata - Class: Actinopterygii - Order: Gasterosteiformes - Family: Gasteroteidae
The three-spined stickleback is very common in British rivers, canals and lakes. In rivers, in particular, it is a fish of the slow-flowing lowland reaches, but because of its habit of colonising tiny bays and backwaters it is sometimes able to thrive in surprisingly swift streams.
In spring the male Stickleback develops a red throat and belly (the male in the picture is a few weeks away from full spawning colours) and it builds a nest from vegetation beside the bank. Sticklebacks usually spawn in May and June. The adults look after their eggs and protect the young larval fish during their first few days of life - an unusual trait for a fish.
The British record 3-spined Stickleback weighed just 4drm; it was caught by Dennis Flack in Cambridgeshire in 1998
At just three or four centimetres when fully grown, the tiny ten-spined stickleback (Pungitius pungitius), is another common species in the north and Britain's freshwater fishes and is most often found in the brackish water of river estuaries or in weedy ponds and ditches.