Sticklebacks – spiny customers

Sticklebacks – spiny customers

Of the two British freshwater sticklebacks, the better known is the three-spined. Careful observation shows that the fish has two obvious long spines on the back and a third smaller one in front of the long-based second dorsal fin. The three-spined stickleback also has a long spine on each side of the belly in place of pelvic fins. ‘Red frotes’?

Most young fishermen, armed with nets, fish for the three-spined sticklebacks in spring, usually calling them tiddlers, but occasionally finding a ‘red-throat’ (or in Essex a ‘red-frote’) as a great prize.

The three-spined stickleback is widely distributed and occurs in most lowland lakes and ponds, streams and rivers in the British Isles. In ponds you can often see it in a few inches of water, hovering above the bottom by moving its large pectoral fins. In flowing water, however, it stays close to cover – bankside vegetation or weedbeds. It isn’t a strong swimmer, so it doesn’t venture into fast currents.

The red-throated stickleback is in fact an adult male in breeding condition. In spring the male builds a nest made of various plants and about the size of a snooker ball, siting it on the river or lake bed. He protects it fiercely from all other males, displaying aggressively by raising and locking his spines and by presenting his bright red underside to the intruders.

He may also flash his red throat at mature females and, with constant darting-and-diving activity, lures or shepherds them towards his nest. The female enters the nest, pushing through the ball of fibres (it doesn’t have a well-defined entrance) to lay her eggs, and the male then joins her to fertilize them.

The male fans the eggs with his large pectoral fins to maintain a supply of oxygen. He also guards the eggs and hatchlings.

The effort of nest-building, breeding and then guarding the nest and eggs is exhausting, and by late summer it is common to find many dead sticklebacks in the water. Females also die in numbers after spawning, presumably because of the stress of egg-production and spawning.

Nine-spined cousin

The nine-spined stickleback resembles the three-spined but has between eight to ten low spines along the back. Both species feed on insect larvae and small crustaceans. The nine-spined stickleback is found all over Britain but not in high numbers. Its preferred habitat is stagnant water, either ponds with dense vegetation and muddy bottoms or streams and ditches which are partly blocked with plants or fallen leaves. You won’t usually find it in open water. The nine-spined stickleback can live in water with very poor oxygen levels.

The male nine-spined stickleback builds a nest for the eggs above the pond bottom in weed beds. His breeding behaviour is very similar to that of the three-spined, but he undergoes less dramatic colour changes.