Three Spined Stickleback Male (Photo: Laurie Campbell)
These cute little fish are smaller than your hand, (about five centimetres long), making them the smallest fish in UK fresh waters. Lots of people call them Tiddlers! They are the only British freshwater fish where doting Dads build a nest for their young.
Three-spined sticklebacks (Gasterosteus aculeatus) are not very strong swimmers and so you see them where the water moves slowly. Good places have muddy or sandy bottoms and water plants for them to hide in. Three-spined sticklebacks can also live in salty water and are often found in pools close to the sea. Sticklebacks are easy to catch with a small net.
Don’t confuse three-spined sticklebacks with their fifteen-spined friends. Fifteen spined stickle-backs have a long snout like a dragon and only live in brackish waters near the sea; you can sometimes find them trapped in rock pools.
Fifteen Spined Stickleback (Photo: Field Studies Council)
Special Features (Adaptations)
Three-spined sticklebacks have bony amour plates on their sides and sharp spines on their backs to stop big fish like trout from eating them. Like minnows young sticklebacks also swim in big groups to confuse the big fish that eat them.
Female three-spined sticklebacks choose their mate by deciding which male has the brightest red belly and does the best zigzag swimming dance.
Sticklebacks make nests for their eggs; males guard their nests from big fish attack.
Life cycle and habitat
In the spring male three-spined sticklebacks build riverbed nests. They make a sticky string to stick water plants together to make a green tent as big as your fist. The males also get sparkling silvery scales on their back, bright blue eyes and a red belly. Then they swim in a crazy zigzag dance to show off to female sticklebacks and scare away other males.
When the female stickleback sees a good dancer she follows him to his nest and puts her eggs inside, the male puts his milt on top and then the eggs can start to grow. The nests of the finest males are visited by lots of females and contain hundreds of eggs.
Male sticklebacks fiercely guard their nest to stop other fish from eating their eggs. To do this the males swim with their tail down and head up, as though they were walking on their tail. This makes them look big and scary to other fish. Dads also use their fins like a fan to move fresh water over their eggs. When young sticklebacks hatch from a nest devoted males spend at least another week guarding them while they learn how to find food and hide from big hungry fish.
When young sticklebacks leave their nest they stick together in big groups for safety and eat water fleas and small insects. As they grow they eat bigger water bugs like worms and water snails. They also like to snack on things that fall into the water such as dead flies. Some sticklebacks spend a little time at sea where they often hide under floating seaweed. After a year or two sticklebacks grow into adults and are ready to build a nest of their own.
The importance of three-spined sticklebacks to Harris
Because they are little, three-spined sticklebacks are good food for lots of creatures that live by or in our rivers such as trout, eels, terns and seagulls. Only five types of freshwater fish are common in Harris, eels, salmon, trout, sticklebacks and charr, so sticklebacks, or tiddlers, are an important part of the variety of life in the freshwaters of Harris (our biodiversity).
by Robin Reid