Three-spined stickleback  (Gasterosteus aculeatus aculeatus)

Biology

This stickleback is an active fish that forms schools (5). Marine three-spined sticklebacks are migratory, whereas freshwater forms tend to be resident (they stay in the same area for life) (2).

Spawning occurs in early spring and summer. The male builds a hollow nest with seaweeds or aquatic plants. After much cajoling by the male, the female lays her eggs inside the nest and the male takes over parental duties, guarding the fertilised eggs and fanning them with his fins to provide them with oxygen (4). The young sticklebacks stay within the safety of the nest until they have absorbed their yolk sacs; they then enter the water where they initially live on plankton (2). After a while they begin to feed on worms, crustaceans, aquatic insects, small fishes and even the eggs and fry of their own species (5).

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