21 May 2019 | Posted in Charlotte Owen , fish
Three-spined Stickleback © Derek Middleton

By Charlotte Owen

WildCall Officer

There are many things to fear if you’re a tadpole.  From ducks and herons to grass snakes and goldfish, everything wants to eat you and one of the most formidable tadpole predators is the stickleback.  We may call them ‘tiddlers’ but shrink down to the size of a tadpole and a stickleback starts to look like a great white shark, complete with a mouthful of razor sharp teeth.

These feisty fish can be found in ponds, lakes, and streams across Sussex.  They can happily live in salt water too, and while you might not guess it they are closely related to seahorses.  Their bodies lack scales but are protected by bony armour plating, and the name comes from the distinctive row of spines just in front of their dorsal fin.  The number of spines varies depending on the species, although the Three-spined Stickleback can have two or four, while the Nine-spined Stickleback has eight to twelve.  The spines can be raised and locked into position in a highly effective defence against predators like the kingfisher, making a stickleback impossible to swallow.

Sticklebacks are aggressive predators themselves and will tackle anything smaller than they are, from water fleas to snails, worms, insect larvae and even other sticklebacks.  Tadpoles don’t stand a chance.  Darting towards its target at top speed, a hunting stickleback opens its jaws so rapidly that the unfortunate victim is drawn straight into its gaping mouth, where it is either swallowed whole or grasped with a powerful bite.  Just like sharks, sticklebacks constantly replace their teeth to maintain sharpness, and some populations have even evolved extra teeth to help them tackle larger prey. 

At this time of year, attention turns to breeding and the silvery-green males develop vibrant blue eyes and a bright red belly.  This acts as a signal to females and a warning to rival males, and they are so sensitive to the sight of red that the merest glimpse will trigger a furious territorial attack.  Each male builds a domed nest from pond weed to attract a passing female, wooing her with a zig-zag dance and defending the resulting eggs with fierce determination.

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