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Stickleback facts for kids

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Four species of stickleback (Gasterosteidae).jpg
Four marine species of stickleback from the Atlantic Ocean coast of North America
Scientific classification


The Gasterosteidae are a family of fish including the sticklebacks. They are related to the pipefish and seahorses.


FishBase recognises 16 species in the family, grouped in five genera. However, several of the species have a number of recognised subspecies, and the taxonomy of the family is thought to be in need of revision.

Although some authorities give the common name of the family as "sticklebacks and tube-snouts", the tube-snouts are classified in the related family Aulorhynchidae.


Genera include:


Sticklebacks are most commonly found in the ocean, but some can be found in fresh water. The freshwater taxa were trapped in Europe, Asia, and North America after the Ice Age, and have evolved features different from those of the marine species.

Sticklebacks are carnivorous, feeding on small animals such as insects, crustaceans and fish larvae.

Sticklebacks are characterised by the presence of strong and clearly isolated spines in their dorsal fins. An unusual feature of sticklebacks is that they have no scales, although some species have bony armour plates.


The maximum size of the best-known species, the three-spined stickleback (Gasterosteus aculeatus), is about 4 inches, but few of them are more than 3 inches long. They mature sexually at a length of about 2 inches. Most other stickleback species are roughly similar in size or somewhat smaller. The only exception is the far larger fifteen-spined stickleback (Spinachia spinachia), which can reach 22 cm (approx. 8.7 inches).


All stickleback species show similar, unusual mating behaviour. The males develop a red breast and construct a nest from weeds held together by secretions from their kidneys, then attract females to the nest. A female lays her eggs inside the nest, where the male fertilises them. The male then guards the eggs until they hatch, and may continue to guard the fry after they hatch. This large investment in both the nesting site and guarding of the eggs limits the number of females a male can mate with. This introduces the ability for selection to favor male mate choice. Some males die following spawning.

Use in science

Faroe stamp 248 stickleback (gasterosteus aculeatus)
1994 Faroe Islands postage stamp with three-spined sticklebacks

The family includes the three-spined stickleback Gasterosteus aculeatus, common in northern temperate climates around the world including Europe, most of northern North America and Japan. Niko Tinbergen's studies of the behaviour of this fish were important in the early development of ethology as an example of a fixed action pattern. More recently, the fish have become a favorite system for studying the molecular genetics of evolutionary change in wild populations and a powerful "supermodel" for combining evolutionary studies at molecular, developmental, population genetic, and ecological levels. The nearly complete genome sequence of a reference freshwater stickleback was described in 2012, along with set of genetic variants commonly found in 21 marine and freshwater populations around the world. Some variants, and several chromosome inversions, consistently distinguish marine and freshwater populations, helping identify a genome-wide set of changes contributing to repeated adaptation of sticklebacks to marine and freshwater environments.

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