A jar full of ‘tom-tiddlers’ is a childhood memory for many. Most of these little fish caught in pools or ditches were three-spined sticklebacks – one of the most common British fishes.

They may be small, but these colourful little fish have a fascinating life.

By April, the male has assumed his breeding finery and is a handsome fish: emerald-green with a bright-red throat patch.

This red colour is an important sign of his breeding condition and a warning to rival males.

In experiments to demonstrate stickleback aggression, a male would attack almost any fish-sized shape which was placed in his territory if it had a red patch on the underside.

The humble stickleback is one of the most widely-studied freshwater fish anywhere, because of their complex behaviour.

The male stickleback lures in potential mates by building a nest of waterweed, detritus and algae which he manoeuvres with his mouth to create a small dome or bower.

He glues these materials together with spiggin, a secretion from his kidneys.

When his nest is ready, he performs an erratic zig-zag dance in the presence of a pregnant female who is persuaded to enter the bower to lay her eggs which he fertilises immediately.

Daddy day care

Once she’s gone, he continues to court more females whose eggs he also fertilises; as his crèche grows, he aerates the eggs by fanning his pectoral fins and chasing off intruders.

When the youngsters hatch, he guards them at first by keeping them close to the nest and even prevents females from cannibalism.

As the young fry grow and swim farther away his fathering instincts begin to falter; the result of old age.

Many sticklebacks live for one year only, which makes his efforts to invest in paternity all the more vital.

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Thank you to Springwatch Flickr group contributor Duncan Cooke for the use of his image.

Illustration by Rose Sanderson.