Outside the breeding season, sticklebacks may be found in loose shoals. They are nocturnal predators, but need quite a lot of light to be able to detect the movement of their prey. They probably hunt more successfully on a moonlit night. They eat all sorts of invertebrates, such as worms, insect larvae, small snails, crustaceans and water fleas. They even eat young fish and fish eggs - sometimes searching out those of other sticklebacks!
When a victim is spotted it is chased if necessary, and the jaws are pushed open and forward very quickly so that the food is sucked in. It is then grabbed by the stickleback's tiny, sharp teeth.
The stickleback itself may be preyed on by larger predators, such as larger fish, kingfishers, herons, water shrews and otters. The spines probably protect it from some of its enemies. When the spines are raised a larger fish may find the stickleback difficult to swallow.Read More: Breeding